Start issues

[Rayson1971]

I've got a 1988 merc 200 black max. Hasn't running on a while. Changed fuel pump diaphragm. Primer bulb fuel to carb. Will fire with start fluid but that's it. I have pulled all carbs and clean out orifices. Any I deas where else to look. ? Even tried an electric. Pump thinking that the mechanical one wasn't working. Has spark on all 6 cylinders. Electrical choke not working. Could it be that?

 

[PilotRyan]

Once you get it running on starting fluid will it continue running? The choke is only there for starting purposes so if that is broken that’s only part of the issue.

Is your bulb holding pressure once primed? Is it fresh fuel?

 

[Rayson1971]

Will not continue running. Fuel not 100% fresh. Primer bulb still full of fuel.

 

[PilotRyan]

In order to completely rule out your fuel system, can you run a brand new fuel line out of a jerry can with new fuel and primer bulb straight to the pump?

This way we can eliminate possibility of collapsed fuel hose liner, clogged tank pickup, etc etc.

 

[Rayson1971]

Still doing same thing with fresh gas. Runs through start fluid and dies. I even pull throttle to see if it'll keep going. Nope

 

[PilotRyan]

ok while you continue trying to diagnose this, try and use fuel and oil in a spray bottle instead to prevent lubrication issues.

If you’re 100% sure you did a good carb rebuild, id go ahead and recheck the fuel pump rebuild you did. If you’re 100% on that then id move to a few different possibilities:

1) cracked or bent reed valves
2) leaking crankcase
3) do a compression check

We need to find out why your carbs aren’t pulling fuel. Needles and seats are often an overlooked item on rebuilds because they don’t appear worn until you look very close

 

[PilotRyan]

Also, try and manually hold the choke butterflies down with your finger when you start if you can. Then when it hopefully pulls fuel you can release them and see if it’ll run

 

[HST4ME]

There is no choke, it's a primer system.

 

[stingray11]

So what are the compression numbers? I would think smooth bore cyl or dead cylinder. Do a leak down test. When was this motor last rebuilt?

 

[Rayson1971]

Well I took the carbs apart one at a time and Chem dipped them thoroughly blew out all the orofices. Notice that some of the needle were stuck. Put it all back together and well low and behold it runs. Sounds good too. I due have a buzzer going off I'll have to figure out. I pulled the oil injection off to run premix. I wonder if it's that? Its a rapid beep. Any ideas?

 

[grumpy88]

Well I took the carbs apart one at a time and Chem dipped them thoroughly blew out all the orofices. Notice that some of the needle were stuck. Put it all back together and well low and behold it runs. Sounds good too. I due have a buzzer going off I'll have to figure out. I pulled the oil injection off to run premix. I wonder if it's that? Its a rapid beep. Any ideas?

Have you tried a different prop ? Sorry buddy i had too ! Lol

 

[Rayson1971]

Lol. Next step.

 

[Rayson1971]

What's the highest I can run the motor with regular water pick up some on the lower? Pickups are 26 inches from back of boat and right now the second hole from the bottom is at bottom of boat

 

[PilotRyan]

What's the highest I can run the motor with regular water pick up some on the lower? Pickups are 26 inches from back of boat and right now the second hole from the bottom is at bottom of boat

This is determined by 1 gauge, but preferably 2. Your water pressure gauge tells you 90% of the story. You raise it up until you start losing your pressure, below 15 PSI on my motor specifically. Then bump it back down 1/4” at a time until you gain that desired pressure back. That is the highest you can run it.

Now, turn your head towards your temp gauge and monitor that. Make sure you’re not exceeding temps. If you’re getting hot, bump her back down again.

 

[Rayson1971]

Kinda figured trial and error. I was gonna run it before I put a low water pickup nose cone on it but I think I'll just do it anyway.

 

[PilotRyan]

Kinda figured trial and error. I was gonna run it before I put a low water pickup nose cone on it but I think I'll just do it anyway.

A lot of people say that if you can’t reach speeds of 75+ a LWP nose cone will actually hinder performance and cause unfavorable handling conditions. Something to read up on if you haven’t done so yet.