Holley Sniper EFI conversion on a 1995 Kachina Icon 25' mcob 454/bravo 1

[Thomas K]

I'm changing out my carb for the Holley Sniper EFi. Looking to get better fuel economy and maybe pick up some ponies. I'm not much of a mechanic but here it goes.

First up is getting the oxygen sensor mounted. I bought a 4x5x1.5 block of aluminum and used the gasket as a pattern for the bolt holes, water, and exhaust.

I was going to attempt to mill this myself on a drill press but I opted to have a pro do it.

I forgot to take a picture of the finished block. I was so excited to get it in.

Drilled and tapped at a 10 degree angle.

02 sensor mounted.

Next up I'm building a base for mounting the new fuel filters and pump. Will post more.

 

[sintax]

nice, and that 10* built into the block is enough to keep everything else exhaust wise lined up?

Are you already plumbed for a fuel return to the tanks?

 

[Thomas K]

nice, and that 10* built into the block is enough to keep everything else exhaust wise lined up?

Are you already plumbed for a fuel return to the tanks?

10 degree is the angle 02 sensor pointed down. The rest of the block is flat. Will post fuel return

 

[sintax]

10 degree is the angle 02 sensor pointed down. The rest of the block is flat. Will post fuel return

oh ok!

I interrupted that as an angle built into the block. Cool, curious to check out your fuel return. Are you just gonna run it back into the filler neck? I'd do this if i had a single fill or a balance line.

 

[Thomas K]

oh ok!

I interrupted that as an angle built into the block. Cool, curious to check out your fuel return. Are you just gonna run it back into the filler neck? I'd do this if i had a single fill or a balance line.

using the filler neck

 

[wet hull]

Great thread and I did this kast year. Your O2 bung is great but you will need this as well. When we tuned the motor we were running rich and when pulling 02 sensor moisture was detected. This fixed it right up and at $80 for a 02 sensor you dont want to keep fouling them. Ran all season and zero issues.

 

[Thomas K]

Great thread and I did this kast year. Your O2 bung is great but you will need this as well. When we tuned the motor we were running rich and when pulling 02 sensor moisture was detected. This fixed it right up and at $80 for a 02 sensor you dont want to keep fouling them. Ran all season and zero issues. View attachment 1087496

Thanks for the advice. I will get one. If I'm looking at this correctly I'm to pull my 02 out, thread the extender in its place and then the 02 goes into the extender?

 

[wet hull]

Thanks for the advice. I will get one. If I'm looking at this correctly I'm to pull my 02 out, thread the extender in its place and then the 02 goes into the extender?

Yes. Very easy and its a nice looking part. You can see it on my right side exhaust riser.

 

[Blackmagic94]

Wouldn’t that make the signal less accurate

 

[wet hull]

Wouldn’t that make the signal less accurate

Not at all according to Brian who tuned my motor in Havasu. This guy knows his shit and he was in my boat on his laptop tuning as we ran through all RPM ranges. I did ask that same question when we started. The ability to run in closed loop is far more beneficial then open as well.

 

[wet hull]

Brain Macy of EFI Store in Lake Havasu

 

[Blackmagic94]

Not at all according to Brian who tuned my motor in Havasu. This guy knows his shit and he was in my boat on his laptop tuning as we ran through all RPM ranges. I did ask that same question when we started. The ability to run in closed loop is far more beneficial then open as well.

Well I hate to say this but it will cause the signal to not be as fast or as accurate. There is a reason why the oem wants the sensor in direct flow and at a certain angle and position before a tail pipe.


Bodies in motion tend to stay in that motion.


If exhaust gas is flowing through the exhaust riser into the manifold it’s got a straight shot now you want it to make a 90° turn and go through a small passage to reach the actual sensor unit of the wide band oxygen sensor. It’s impossible for the exhaust gas to actually have a fast in an accurate signal in that position.

 

[Thomas K]

Well I hate to say this but it will cause the signal to not be as fast or as accurate. There is a reason why the oem wants the sensor in direct flow and at a certain angle and position before a tail pipe.


Bodies in motion tend to stay in that motion.


If exhaust gas is flowing through the exhaust riser into the manifold it’s got a straight shot now you want it to make a 90° turn and go through a small passage to reach the actual sensor unit of the wide band oxygen sensor. It’s impossible for the exhaust gas to actually have a fast in an accurate signal in that position.

I do have the recommended 10 degree of angle down into the exhaust. I'm hoping that should do the trick but I do not want to fry my new stuff.

 

[Blackmagic94]

I do have the recommended 10 degree of angle down into the exhaust. I'm hoping that should do the trick but I do not want to fry my new stuff.

Just run it. Sensors are cheap if they foul. If your tune is on the sensor will be good to go for a long time. As long as water isn’t hitting it

 

[Thomas K]

I have very limited space in my engine bay. The best solution I could come up with for mounting my new pump and filters is just above the transom. I will be using the tow hook hardware to hold a plywood base to mount them to.

Just coated the plywood with epoxy resin and will use bilge paint next

 

[wet hull]

Just run it. Sensors are cheap if they foul. If your tune is on the sensor will be good to go for a long time. As long as water isn’t hitting it

How is that? The sensor Holley sniper requires is their brand or the Bosch. They are $80-$125 each. I do agree if he can get it tuned prior to fouling he can lock that tune and run in open loop. If he wants to run in closed loop and have the system adapting to conditions at all times, the minute he fouls he is dead in the water. Only way around this is to have the Sniper dash so he can access the tune on the water and switch to open loop to eliminate O2 sensor. I have the dash in my boat and love it. Worth every penny.

We did start my tune without the extender. Sensor made it halfway. What we think is happening that when motor is off the steam leftover condinsates. Once it gathers on walls of exhaust and you fire back up it blows across sensor and fries it. Brian told me the computer does not require alot of 02 and therefore the extender works for boat/ holley applications, but he was also able to adjust all parameters to make a perfect tune for me. This was at a cost of $800 for 4 hours of work. The OP just needs to plan on having someone tune his motor on the water, lock that tune and have a worry free season.

To the OP, its a pain to get there but once you do you will love the system. The other item we added was oil pressure, water temp, water pressure and battery min/ max specs and if reached we go into a limp mode that keeps me at 1200 rpm or less so I can idle back to trailer if needed. This is how we found my low oil pressure do to worn rings. We ate enough oil that weekend my pressure would drop if boat leaned to side going over wakes. Went into limp mode. Saved my motor from going boom at end of season.

 

[Blackmagic94]

They use Bosch lsu4.9 sensors.


All snipers come with the dash.

 

[02HoWaRd26]

Just run it. Sensors are cheap if they foul. If your tune is on the sensor will be good to go for a long time. As long as water isn’t hitting it

Sensors at 80-100$ are cheap until you burn a few up, or worse come out for the weekend and burn that spare so now your boat is a canoe. But your budget must be a lot better than some.
!

 

[Blackmagic94]

Sensors at 80-100$ are cheap until you burn a few up, or worse come out for the weekend and burn that spare so now your boat is a canoe. But your budget must be a lot better than some.
!

I’ve never had a wideband fail that fast in my life. Sounds like a shit tune. Turn off the closed loop function with the dash if you are worried about it once the tune has completed the self learn

 

[rush1]

Following , I've been wanting to put this on my boat but wanted to see how it works first.

 

[John Taylor]

Yeah , following. I would love to do this to my 540. I am running closed cooling . The problem I have is getting the temp to stay at 160 or above. off plane she gets warm but while running I dip down into the 140ish range. The imco lower flows a lot more water through the heat exchanger.

 

[DaveH]

if you are killing 02 sensors the MOST likely reason is moisture in the exhaust.

the "self learn" these systems offer is NO SUBSTITUTE for a proper tune. bumpy cams cause the 02 reading to be highly inaccurate and the ecu can not self learn around that.

 

[wet hull]

if you are killing 02 sensors the MOST likely reason is moisture in the exhaust.

the "self learn" these systems offer is NO SUBSTITUTE for a proper tune. bumpy cams cause the 02 reading to be highly inaccurate and the ecu can not self learn around that.

I agree fully. Mine was moisture. I run closed loop but had a full tune done on the water and there is definitely no way the self learn could have woke my motor up the way Brian did.

 

[Ace in the Hole]

Had this system on both motors of my last cruiser...the o2 spacer was a must..without it I had to constantly fuck with it. Also had to space it (the unit itself) off the manifold to clear things as well. Once it runs right its great..but it wasn't an instant deal. Looking forward to seeing how it goes for you.

 

[Thomas K]

Thanks for the advice guys! I just received my bung extender. Its looking like nasty weather this week so I probably will not get it installed until this weekend.

 

[Nanu/Nanu]

Thomas! Your setup looks very nice. One of these days you should post your pics of the transom rebuild you did.

Keep up the good work!

 

[Thomas K]

Thomas! Your setup looks very nice. One of these days you should post your pics of the transom rebuild you did.

Keep up the good work!

I will do

 

[Thomas K]

I decided I better pull my exhaust 02 mounting block to check and see how far the bung extender was in the exhaust flow. Bummer deal, it is over half blocked. l sent the block and the bung extender back to the shop. I'm getting it milled a little more so the extender will operate correctly.

 

[Thomas K]

With the added 1-1/2 of height in the exhaust riser, there was just too much stress on all of the other sections of exhaust to get it all fitted up. I split my pipe and added another boot to relieve the stress.

 

[Thomas K]

Fuel pump and filter mounting block installed at transom.

 

[Thomas K]

I got my 02 sensor mounting block and bung extender back from the shop. Now the extender is in the right spot

Here it is on the manifold

I decided to go with nylon braided fuel lines and 6an fittings. I should have sprung for the steel braided lines. Some of the 6an fittings wanted to bunch up the outside braiding while getting the fittings put together. I used my angle grinder with metal cutoff wheel to cut the lines. After I cut them, I flushed them out my garden hose and them used compressed air to blow them out and dry.

I have 1/2 in pinch clamps for pex plumbing pipes and they worked great to secure my lines where I could not use the 6an fittings

Fuel pump and filters mounted.

 

[wet hull]

I got my 02 sensor mounting block and bung extender back from the shop. Now the extender is in the right spot View attachment 1105813


Here it is on the manifold

View attachment 1105814


I decided to go with nylon braided fuel lines and 6an fittings. I should have sprung for the steel braided lines. Some of the 6an fittings wanted to bunch up the outside braiding while getting the fittings put together. I used my angle grinder with metal cutoff wheel to cut the lines. After I cut them, I flushed them out my garden hose and them used compressed air to blow them out and dry. View attachment 1105815


I have 1/2 in pinch clamps for pex plumbing pipes and they worked great to secure my lines where I could not use the 6an fittings View attachment 1105817

Fuel pump and filters mounted.

View attachment 1105819

Looking good! Sounds good as well!

 

[Blackmagic94]

I would not recommend running a fuel pump higher then the tank level. Low is a must.



Any why aren’t you using the correct AN fittings? That looks like a fire in the making.

 

[Thomas K]

I would not recommend running a fuel pump higher then the tank level. Low is a must.



Any why aren’t you using the correct AN fittings? That looks like a fire in the making.

With my boat, Kachina stuffed the motor in as tight as tight as they could get it. On either side are the fuel tanks, batteries, and trim pump motor. There is just not room for anything else or any spot to mount a pump low.

The pump and fuel filters have barbed ends...... so I used clamps. AN fittings on the rest.

 

[Blackmagic94]

With my boat, Kachina stuffed the motor in as tight as tight as they could get it. On either side are the fuel tanks, batteries, and trim pump motor. There is just not room for anything else or any spot to mount a pump low.

The pump and fuel filters have barbed ends...... so I used clamps. AN fittings on the rest.

Ok i get that but problems



First you dont run braided hose with push lock barbed fittings, you run push lock hose which is different and not braided


Second


The pump should be as close to the fuel lines to the tank as possible if you cant mount below the tank, but having the pump where you have it will cause long term issues I promise.

 

[Thomas K]

Here is the 02 sensor installed with the bung extender. I don't have to use the special 02 socket to loosen for tighten the sensor now, and that is nice

Removing the carb was pretty easy. The old fuel pump was easy to block off with a plate. The Mercathode support bracket needed a little modifying to allow room for the vacuum lines on the efi. I did not have any vacuum lines to the old carb. The valve covers vented to the flame arrestor. I was just going to put some breathers on the covers. What I did not realize is that the efi unit has to have the 3/8 vacuum line hooked up to function properly. The brake booster vacuum line, I connected to pcv valves, and put a oil filler neck breather on.

All hooked up and wired

The efi wizard is fairly straight forward. I'm not controlling the timing so its pretty basic. After the setup, we got the fire extinguishers out just in case. A few never's for that initial crank.... no go. Oh Geez! Gotta flip the kill switch!
Holy crap, she fired right up!

I spent maybe 30mins adjusting the idle screw to get the iac to 0%-5%. It has never idled this nice before

 

[Runs2rch]

With my boat, Kachina stuffed the motor in as tight as tight as they could get it. On either side are the fuel tanks, batteries, and trim pump motor. There is just not room for anything else or any spot to mount a pump low.

The pump and fuel filters have barbed ends...... so I used clamps. AN fittings on the rest.

Like BlackMagic said above.

They are Push Lok not barbed.

 

[Blackmagic94]

Mounting a pump above the fuel fill line in a storage tank creates air pockets. When the engine is off the air will raise to the highest point which will be your pump, every time you go to prime the fuel system for start it will be cavate against the air and may or may not self prime the 10-20' of fuel line from the tank to the filter to the pump. This will cause wear to the pump but as stated earlier you may never get fuel to the pump to make the engine run to begin with.

 

[Thomas K]

Mounting a pump above the fuel fill line in a storage tank creates air pockets. When the engine is off the air will raise to the highest point which will be your pump, every time you go to prime the fuel system for start it will be cavate against the air and may or may not self prime the 10-20' of fuel line from the tank to the filter to the pump. This will cause wear to the pump but as stated earlier you may never get fuel to the pump to make the engine run to begin with.

Okay well I may be the biggest dummy. In my earlier post you can see the fuel pump with no hose on it. Your saying that is not a barb fitting but a push lock? My fuel tanks are in the engine compartment. From the pickup hose it is less than 4ft to the fuel pump

 

[Thomas K]

Like BlackMagic said above.

They are Push Lok not barbed.

Please explain to me how this is push lock

 

[Nanu/Nanu]

@Thomas K I imagine these were supplied terminations from Holley

@Blackmagic94 @Runs2rch are you talking about these push-lock hose terminations?

How do you secure the hose on a push-lock fitting? All the pictures ive seen are with traditional hose clamps or pex like Thomas has used. Is there different hardware? Do you have pics?

I'm interested now...

 

[Blackmagic94]

barbed fittings are push lock


Push lock hose is never braided, its just solid rubber that says push lock on it etc. You need hose that handles 100 psi or more, rubber fuel line at the hardware store isnt going to work. Push lock hose when done correctly does not need a clamp.

 

[counterpart7]

barbed fittings are push lock


Push lock hose is never braided, its just solid rubber that says push lock on it etc. You need hose that handles 100 psi or more, rubber fuel line at the hardware store isnt going to work. Push lock hose when done correctly does not need a clamp.

Barbed fittings are not Push-lock. Push-lock fittings are Push-lock and Barbed fittings are barbed…

The fittings and hoses the OP used look to be what is supplied directly from Holley in the Sniper Kit. I’m not saying Push-lock hoses wouldn’t be better(they are), but OP looks to be using exactly what Holley specs for this kit. In a boat, I would run something stronger and less susceptible to leaks.

I do agree with finding a way to mount the fuel system bellow the fuel tank like stated earlier!

 

[Thomas K]

barbed fittings are push lock


Push lock hose is never braided, its just solid rubber that says push lock on it etc. You need hose that handles 100 psi or more, rubber fuel line at the hardware store isnt going to work. Push lock hose when done correctly does not need a clamp.

Dude you assume way to much. I didn’t get my fuel lines from a hardware store. I got them from hobby lobby.

 

[Thomas K]

@Thomas K I imagine these were supplied terminations from Holley

@Blackmagic94 @Runs2rch are you talking about these push-lock hose terminations?

View attachment 1106758
How do you secure the hose on a push-lock fitting? All the pictures ive seen are with traditional hose clamps or pex like Thomas has used. Is there different hardware? Do you have pics?

I'm interested now...

@Nanu/Nanu You are correct. They are the supplied terminations from Holley

 

[renodaytona]

Any updates? Depending on if I keep the Daytona I might be installing the dual 4500 system on my blower motor and having Brian at the EFI store do the tune and lock it out. I out the Holley system on my Tatum sand car with an LS1 and it is so much better than the hacked Delphi system that was on it.

 

[Thomas K]

Update. I did some other things to my boat as well. New ignition switch, new solenoids on my trim pump motor because my outdrive would not come up, even with the trailer switch. New engine control throttle shifter because my old quicksilver 3000 I really didn't like, and lubed my cables. Now I'm lake ready?
My wife and I did a shake down cruise last weekend to Lake Pleasant. She fired right up with no long crank times which was nice. When I tested the engine idle with the hose, it was very nice. Not so good on the water. My exhaust tips are below the water line when at idle. I think the added back pressure of the exhaust and actual load on the prop when in gear made for a rough idle and stalling when put into gear. My target rpm at idle was 750. I'm going to up it to 800-850 rpm. Hopefully that will fix it. Accelerating and on plane, she ran very smooth. Very responsive and she did not stumbling at any rpm. We cruised around for about 5 min. The engine temp was around 150 according to the handheld dash and so it was not into learn mode yet. I went to do a wot run to see if I could get the temp up a bit and the throttle handle went limp at 4400rpm. I thought the cable broke. After poking around a bit I found the problem.

The plastic retainer nut broke off the cable. The left cable in the photo is the throttle with the broken nut, the right is the shift cable. The shift cable nut has stress fractures in it as well. Not good.
So I disconnected the throttle cable at the motor and operated the throttle by hand while holding the engine hatch open a bit to get my arm in there while my wife drove. Haha kinda funny.
We tried to make the most of the day but it was getting really windy so we called it. My wife did great job getting back on the trailer considering the wind ,no throttle, and stalling. I pulled the plug and a ton of water came out of the bilge. Usually it is bone dry. Turns out the shift cable bellows has a big tear in it. Pretty disappointing because I replaced the bellows last year.
I was pleased with how the sniper operated. On the motor, I'm going to swap the location of the temp sensor for the efi with the dashboard temp sensor. The dash was reading around 180 while the efi 150. I hope that will make a difference to get the sniper into learn mode. Also up my target idle speed a bit.
I ordered all new cables and a bellows kit. Today I'm pulling the outdrive to do the lower shift cable and bellows.

 

[Blackmagic94]

You can change the min learn temp or disable it.

 

[rivermobster]

Update. I did some other things to my boat as well. New ignition switch, new solenoids on my trim pump motor because my outdrive would not come up, even with the trailer switch. New engine control throttle shifter because my old quicksilver 3000 I really didn't like, and lubed my cables. Now I'm lake ready?
My wife and I did a shake down cruise last weekend to Lake Pleasant. She fired right up with no long crank times which was nice. When I tested the engine idle with the hose, it was very nice. Not so good on the water. My exhaust tips are below the water line when at idle. I think the added back pressure of the exhaust and actual load on the prop when in gear made for a rough idle and stalling when put into gear. My target rpm at idle was 750. I'm going to up it to 800-850 rpm. Hopefully that will fix it. Accelerating and on plane, she ran very smooth. Very responsive and she did not stumbling at any rpm. We cruised around for about 5 min. The engine temp was around 150 according to the handheld dash and so it was not into learn mode yet. I went to do a wot run to see if I could get the temp up a bit and the throttle handle went limp at 4400rpm. I thought the cable broke. After poking around a bit I found the problem.
View attachment 1115832

The plastic retainer nut broke off the cable. The left cable in the photo is the throttle with the broken nut, the right is the shift cable. The shift cable nut has stress fractures in it as well. Not good.
So I disconnected the throttle cable at the motor and operated the throttle by hand while holding the engine hatch open a bit to get my arm in there while my wife drove. Haha kinda funny.
We tried to make the most of the day but it was getting really windy so we called it. My wife did great job getting back on the trailer considering the wind ,no throttle, and stalling. I pulled the plug and a ton of water came out of the bilge. Usually it is bone dry. Turns out the shift cable bellows has a big tear in it. Pretty disappointing because I replaced the bellows last year.
I was pleased with how the sniper operated. On the motor, I'm going to swap the location of the temp sensor for the efi with the dashboard temp sensor. The dash was reading around 180 while the efi 150. I hope that will make a difference to get the sniper into learn mode. Also up my target idle speed a bit.
I ordered all new cables and a bellows kit. Today I'm pulling the outdrive to do the lower shift cable and bellows.

Not bad! You have an IO, right? 850 might be a bit high for that.

Keep messing with it. You'll get it.

 

[Streetmoto]

Update. I did some other things to my boat as well. New ignition switch, new solenoids on my trim pump motor because my outdrive would not come up, even with the trailer switch. New engine control throttle shifter because my old quicksilver 3000 I really didn't like, and lubed my cables. Now I'm lake ready?
My wife and I did a shake down cruise last weekend to Lake Pleasant. She fired right up with no long crank times which was nice. When I tested the engine idle with the hose, it was very nice. Not so good on the water. My exhaust tips are below the water line when at idle. I think the added back pressure of the exhaust and actual load on the prop when in gear made for a rough idle and stalling when put into gear. My target rpm at idle was 750. I'm going to up it to 800-850 rpm. Hopefully that will fix it. Accelerating and on plane, she ran very smooth. Very responsive and she did not stumbling at any rpm. We cruised around for about 5 min. The engine temp was around 150 according to the handheld dash and so it was not into learn mode yet. I went to do a wot run to see if I could get the temp up a bit and the throttle handle went limp at 4400rpm. I thought the cable broke. After poking around a bit I found the problem.
View attachment 1115832

The plastic retainer nut broke off the cable. The left cable in the photo is the throttle with the broken nut, the right is the shift cable. The shift cable nut has stress fractures in it as well. Not good.
So I disconnected the throttle cable at the motor and operated the throttle by hand while holding the engine hatch open a bit to get my arm in there while my wife drove. Haha kinda funny.
We tried to make the most of the day but it was getting really windy so we called it. My wife did great job getting back on the trailer considering the wind ,no throttle, and stalling. I pulled the plug and a ton of water came out of the bilge. Usually it is bone dry. Turns out the shift cable bellows has a big tear in it. Pretty disappointing because I replaced the bellows last year.
I was pleased with how the sniper operated. On the motor, I'm going to swap the location of the temp sensor for the efi with the dashboard temp sensor. The dash was reading around 180 while the efi 150. I hope that will make a difference to get the sniper into learn mode. Also up my target idle speed a bit.
I ordered all new cables and a bellows kit. Today I'm pulling the outdrive to do the lower shift cable and bellows.

There's a Air Conditioning feature in the Sniper software that proactively ups the idle to compensate for the extra load of the AC compressor. It's a one wire trigger that can potentially be tied into the safety switch in your shifter to come one when you put the boat in gear (might need to be used in conjunction with a "normally on" relay). Hope that helps!