502 vs. 496 vs. 454 (7.4 MPI) WARNING: Boating Content

[DragDad]

Ok, I am getting close to buying a boat and I have heard all kinds of issues with Mercruiser computers (wadeva they are called). I hear about engine codes shutting down the boat in error, I hear the 502 does it more than the other two.. I hear the 454 is most reliable... I hear 496 is the way to go. All this scares me. I'm thinking about just going old school without the computer control.

Anyone got an opinion? (opinions are like assholes.. everyone's got one).

 

[RiverDave]

I know a lot of guys with the 502 Mag, and the original 454 Mag.. I don't think anybody I know has ever had a problem with either of those motors, they are pretty bullet proof. The early 496's had a bunch of problems, but I think they are all sorted out now.

personally I would go EFI over Carb's, unless you plan on supercharging it down the road etc..

RD

 

[Bobby V]

I have over 500 hours on my 502 EFI 98' 25' Eliminator Eagle. Never had a problem at all. (knock on wood)..

 

[fmo24]

I have a '98 502 efi and never a hiccup. starts everytime and runs great. hope i did not jinx myself now LOL

 

[HBCraig]

I have an '04 496HO and it has been a good motor thus far knock on wood. I had to replace a water pressure sensor and that is it. But, I am about ready to replace the entire water pump housing. The impeller is replaced every year and they wear down easily to the point the housing gets worn.

If I were to do it all over again I would buy a N/A motor from a reputable builder and lose the computer stuff.

 

[RiverDave]

I have an '04 496HO and it has been a good motor thus far knock on wood. I had to replace a water pressure sensor and that is it. But, I am about ready to replace the entire water pump housing. The impeller is replaced every year and they wear down easily to the point the housing gets worn.

If I were to do it all over again I would buy a N/A motor from a reputable builder and lose the computer stuff.

Get the stainless one from CP.. Lifetime housing, 300 bucks.

RD

 

[HBCraig]

Get the stainless one from CP.. Lifetime housing, 300 bucks.

RD

Cool. Good to know. Al Stoker has machined mine for the last time and it is down to getting a new one.

 

[DragDad]

Im so damned proud of you guys....
I posted a clearly boating oriented thread, and you all shined with blazing colors.

Truly, my faith in RDP and humanity in general has been restored.

sniffle.... wiping a tear from my cheek.
:blah:arty2::blah:arty2::blah:

 

[Duffster]

I have a efi 502 mag with low hours. Had a vapor lock issue on the injector tank on hot days that took so time to sort out. But now it runs bitchen a hell of a lot better than the carbed 454 mag I was running before.

 

[rivermobster]

I know a lot of guys with the 502 Mag, and the original 454 Mag.. I don't think anybody I know has ever had a problem with either of those motors, they are pretty bullet proof. The early 496's had a bunch of problems, but I think they are all sorted out now.

personally I would go EFI over Carb's, unless you plan on supercharging it down the road etc..

RD

what he said ^^^

 

[milkmoney]

i have a 496 mag 07' this dam engine runs like a champ. always starts and idles perfect and runs when need to. bullet proof motor as far as i am concerned. also maintaince is the key like all other engines...

they way it was explained to me is that it has a computer watching the computer so it will shut down and take over, if it detects a problem thats seriuos enough.. like only going to 5mph to get ya back to the ramp etc...

 

[sdpm]

Now if they only had an engine with a 3rd computer that could watch over the other 2. You just never know!

 

[Motor Boater]

I have a 2001 502 EFI and have had no issues other than a coil go bad. The 502's are known for burning some oil though. Mine is one of the good ones and hardly uses any. It only has 225 hours though so its fairly young.

 

[DragDad]

Im looking at an injected 502... so all of this gives me a warm fuzzy feeling.
Thanks guys!

 

[NicPaus]

My 454 MPI has been bulletproof. Has not burned a drop of oil in 10 years. Burns fuel like a honda. 15 gallons on saturday and towed tubers off the shore for 3 hours several trips to roadrunner and up to the dam and back.

 

[HBCraig]

BTW, my 496HO takes a little oil but not a lot. I put about 2 quarts in over the entire summer.

 

[Duffster]

MaddogMateo,
Attached is a diagram of the efi 502 VST tank. To fix your vapor lock problem flip the spring and seal around circled. Make sure the seal
is on the bottom not how it's pictured in the diagram. The way they have it the tank gets very little air and causes the vapor lock issue on hot days.

This was an instant problem when I put the efi motor in at first I thought it was the low pressure fuel pump.
It took me some time to figure out but now It runs great no issues.

Craig

 

[WET-N-WILD LIGHTNING]

I have a 05 496HO with 118hrs on it and have had no issues. Great motor

Get the stainless one from CP.. Lifetime housing, 300 bucks.

RD

Thanks for the info

 

[charlyox]

I have an '01 496 H.O. with 444 hours. No issues.

 

[92562]

'05 490 MAG HO with a Whipple. 165 problem free hours and lots of this!

 

[HBCraig]

'05 490 MAG HO with a Whipple. 165 problem free hours and lots of this!

How much boost are you running?

 

[Kleptow]

502 No problems since I re-flashed the ECM.

 

[Trash]

Not a big block, but I had a 1995 Merc 350 Mag EFI/MP with 734 hours and the EFI was flawless. It ALWAYS started. It could sit on the trailer for months, fire up within seconds, bang it into gear and NEVER even hiccup.

In fact I'm going to utilize the same EFI system on the rebuild I'm currently knee deep in.

 

[MaddogMateo]

MaddogMateo,
Attached is a diagram of the efi 502 VST tank. To fix your vapor lock problem flip the spring and seal around circled. Make sure the seal
is on the bottom not how it's pictured in the diagram. The way they have it the tank gets very little air and causes the vapor lock issue on hot days.

This was an instant problem when I put the efi motor in at first I thought it was the low pressure fuel pump.
It took me some time to figure out but now It runs great no issues.

Craig

Yep thats it, I will check it out thanks!

 

[TPC]

I'm no expert, this is just an armchair observation.

Most everyone uses the GM Vortex blocks for their gas motors.
The variation between builders seems to be with the computers and accessories like the pick-up/sea pump, alternators, cats, belt and hose pathways etc.,,, we're told.
Someone correct me if I'm wrong. I always appreciate a teachable moment.

Our Merc's have been flawless, our Marine Power versions have been frustrating nightmares with the electronics.
Run amazing when the conditions are right and the computer likes what it reads,,, but,,,, it would bite us on the ass un-expectantly,, and at the worst possible time.

We just happened to mention the fuxstory intermittent engine issues on Hotboats and some sharp MoFo poster had gone through the same nightmares with his Marine Power engine.
A one-and-done poster, he was a Univac with programs,, figured out the re-programming on his own,, and passed on the info to us,, and how and where to go to fix it.

Nothing like launching on the river, then the NEW engine pukes because the computer is stepping on it's dick,,,, and you're drifting toward the rocks with a direct drive and a boatload of kids.

We went with the NEW design for 2012 Merc 502 on the latest boat (if we ever find what became of it, but that's another fuckstory).
Extreme Limited availability if you're thinking new purchase.
Jump now or ya won't get one in time.

I don't mind being a Pioneer with new design motors,, but so far,, like all Pioneers, I usually just end up with arrows shot in my ass.

 

[RiverDave]

I'm no expert, this is just an armchair observation.

Most everyone uses the GM Vortex blocks for their gas motors.
The variation between builders seems to be with the computers and accessories like the pick-up/sea pump, alternators,, belt and hose pathways etc.,,, we're told.
Someone correct me if I'm wrong. I always appreciate a teachable moment.

Our Merc's have been flawless, our Marine Power versions have been frustrating nightmares with the electronics.
Run amazing when the conditions are right and the computer likes what it reads,,, but,,,, it would bite us on the ass un-expectantly,, and at the worst possible time.

We just happened to mention the fuxstory intermittent engine issues on Hotboats and some sharp MoFo poster had gone through the same nightmares with his Marine Power engine.

I forget who it was, but he was a univac with programs,, figured out the re-programming on his own,, and passed on the info to us,, and how to fix it.

Nothing like launching on the river, then the NEW engine pukes because the computer is stepping on it's dick,,,, and you're drifting toward the rocks with a direct drive and a boatload of kids.

We went with the NEW for 2012 Merc 502 on the latest boat (if we ever find what became of it, but that's another fuckstory).
Extreme Limited availability if you're thinking new purchase.
Jump now or ya won't get one in time.

I don't the mind be a Pioneer with new design motors,, but so far,,to be a Pioneer I usually just end up with arrows shot in my ass.

LMAO..

RD

 

[purrfecttremor]

2004 496 HO with over 200hrs and always turn key. Just routine service and it runs like a champ every trip.

 

[92562]

How much boost are you running?

5.5lbs max.

 

[WET-N-WILD LIGHTNING]

'05 490 MAG HO with a Whipple. 165 problem free hours and lots of this!

What kind of internal work did you do to the motor before you added the whipple? Who did the work? What drive are you using?

 

[NoDoz]

another vote for the 502 EFI and yes knock on wood as well, no problems. have K&N airfilter, EMI thunder exhaust, AZ Speed and Marine chip.Engine sounds and runs great.

 

[NoDoz]

http://www.youtube.com/watch?v=r-6nkAH4gDs&feature=player_embedded#at=14

sounds a lot better and louder in person. If you have a nice sound set-up on your home computer with bass/subwoofer you get a better idea.

 

[Duffster]

another vote for the 502 EFI and yes knock on wood as well, no problems. have K&N airfilter, EMI thunder exhaust, AZ Speed and Marine chip.Engine sounds and runs great.

How much difference did the AZ Speed and Marine chip make? I have EMI thunder exhaust on mine.
Is it really worth getting them tuned?

 

[NoDoz]

How much difference did the AZ Speed and Marine chip make? I have EMI thunder exhaust on mine.
Is it really worth getting them tuned?

http://www.azspeed-marine.com/peecuca.html

Unfortunately I don't have the answer, maybe someone can chime in. The owner before me did the work.

 

[92562]

What kind of internal work did you do to the motor before you added the whipple? Who did the work? What drive are you using?

No internal work, I did the install, XR drive. The key is in the ECU, don't let it detonate and Whipple did the flash (and re-flash - the first one was too fat).

 

[WET-N-WILD LIGHTNING]

No internal work, I did the install, XR drive. The key is in the ECU, don't let it detonate and Whipple did the flash (and re-flash - the first one was too fat).

Really!!??? I have talked to 3 shops and they all told me not to add the whipple without doing internal work is about $12000 plus the whipple. You haven't had any issues with it? I have an X drive would it handle the whipple?

 

[92562]

Really!!??? I have talked to 3 shops and they all told me not to add the whipple without doing internal work is about $12000 plus the whipple. You haven't had any issues with it? I have an X drive would it handle the whipple?

I know several people who have the same combo (many did the work themselves) and all are still running great. You just have to be aware of gas quality and be sure it's set up right at the start (fuel pressure, etc.). I would not try this combo with less than an XR. If you want detail, PM me so we don't highjack this thread.

---Rob

 

[WET-N-WILD LIGHTNING]

I know several people who have the same combo (many did the work themselves) and all are still running great. You just have to be aware of gas quality and be sure it's set up right at the start (fuel pressure, etc.). I would not try this combo with less than an XR. If you want detail, PM me so we don't highjack this thread.

---Rob

 

[Blazen Js]

I vote 7.4MPI over 496...don't have any friends with the 502? My cousin has had several cooling system issues with his stock 496. I think the water pickup is low on his drive compared to my 7.4MPI motor which is approaching 350 hours without a hiccup.

 

[Denniston]

Ok, I am getting close to buying a boat and I have heard all kinds of issues with Mercruiser computers (wadeva they are called). I hear about engine codes shutting down the boat in error, I hear the 502 does it more than the other two.. I hear the 454 is most reliable... I hear 496 is the way to go. All this scares me. I'm thinking about just going old school without the computer control.

Anyone got an opinion? (opinions are like assholes.. everyone's got one).

 

[Denniston]

Hi. I'm I the same boat as you except the boat I'm looking at has three Merc 502's in it. I've been interested in diesel powered cruisers before, but this boat is gas powered. Always heard diesel was the preferred power plant due to reliability.
What am I getting into in possibly buying a 1997 502 powered Sunseeker? The man says he's had the same mechanic since he bought it oroginally.

 

[HCP3]

Welcome to the forum. One hell of a thread resurrection.

 

[Denniston]

Welcome to the forum. One hell of a thread resurrection.

... Well thanks.... I had to really try!!!

 

[Universal Elements]

Hi. I'm I the same boat as you except the boat I'm looking at has three Merc 502's in it. I've been interested in diesel powered cruisers before, but this boat is gas powered. Always heard diesel was the preferred power plant due to reliability.
What am I getting into in possibly buying a 1997 502 powered Sunseeker? The man says he's had the same mechanic since he bought it oroginally.

That is a lot of $ for gasoline per hour.

 

[Tank]

I think it's pretty common industry knowledge Mercury black motors are tried and true. I've had a 454 and two 496HO's, great motors. and 3 or 4 or 5 (depending if you're counting rebuilds ) 525SC's.

Did drag dad ever settle on which motor he was going to buy?

 

[Tank]

Hi. I'm I the same boat as you except the boat I'm looking at has three Merc 502's in it. I've been interested in diesel powered cruisers before, but this boat is gas powered. Always heard diesel was the preferred power plant due to reliability.
What am I getting into in possibly buying a 1997 502 powered Sunseeker? The man says he's had the same mechanic since he bought it oroginally.

Are you referring to the Sunseeker Apache in Huntington Beach? Owned by Nort Alderson? That boat has been maintained and upgraded with an open checkbook. I don't think you'll find a cleaner one. And, I'd leave the 502's for now. They're virtually brand new and have been dialed in and completely trouble shot out.

 

[Socalx09]

I don’t know much about engines and mechanics, but the 454 in the boat ran for 27 years. I forgot the hours since it was reset with the rebuilt engine (Brought a rebuilt engine) , but’s its written down somewhere. But, it was used a lot I can tell you that!

My dad had a 454 SS truck that had around 325k miles before the engine went out. So I would say the 454 engine has been good!

 

[guest hs]

Absolutely can not go wrong with a 454 or 502 mag or 500 efi

 

[dribble]

03 496 Mag and never an issue. My second trip out my buddies dog swallowed a fish hook and was bleeding from his stomach. With only two hours on the engine I drove that boat wide open and fully trimmed out for 25 minutes to get the dog to the dock. The boat has run perfect ever since and never burned one drop of oil.

 

[Blackmagic94]

Crystal died on my 496 mag. 500 dollar fix via whipple. Sold the boat with 790 hours and still ran strong

 

[Denniston]

It's a Super hawk 50.
I think it's fuel burn may eat me alive.

Are you referring to the Sunseeker Apache in Huntington Beach? Owned by Nort Alderson? That boat has been maintained and upgraded with an open checkbook. I don't think you'll find a cleaner one. And, I'd leave the 502's for now. They're virtually brand new and have been dialed in and completely trouble shot out.