Having issues keeping my 25HP OMC running, and above idle

I posted about this on thehulltruth.com as well since its more active https://www.thehulltruth.com/boating-forum/673047-carb-adjustment-help-25hp-omc.html

But, thought I'd ask here as well since you guys have more experience with small motors.

Engine runs but dies after idling about 30 seconds, or dies if you take it above a high idle within about 2 seconds.

I rebuilt the fuel pump. Definitely getting fuel now - I confirmed it is delivering fuel.

Engine will idle for about 30 seconds before cutting out.

If you take it above about 1/3rd throttle it dies immediately.

Its very hard to restart it and takes 20-25 seconds of cranking usually.

It will start up the first time almost immediately, but subsequent restarts are very hard.

I've taken the carb apart and cleaned the heck out of it.

I don't have much experience adjusting a carb.

Does this sound like a carb issue?

I'm wondering if it could be a coil pack, since it runs well cold, but starts acting worse as it warms up.

I also noticed a nasty ring of oil in the test bucket.



I'm running 50:1. Is this amount of oil expected? It only ran about 2-3 minutes in total.

Lugo, glad to see you made it through the fuel pump rebuild.

how did it run last week when you and your dad went out ?

and with my 25hp of the same vintage, yes, that amount of oil is about normal. (from my experience).

Barefoot_Johnny said:

Lugo, glad to see you made it through the fuel pump rebuild.

how did it run last week when you and your dad went out ?

and with my 25hp of the same vintage, yes, that amount of oil is about normal. (from my experience).

Click to expand...

Johnny -

Engine did not run well when we took it out. It would die as soon as you put it in gear, was hard to start after the first time it went to idle, and wouldn't stay running above idle. Same thing as its doing now.

Fuel pump wasn't difficult, just lots of small parts. Pretty simple, I went slow and took pictures of each stage as I went.

So not fuel pump is ruled out.

Start your idle mixture setting at a rich 1 1/2 turn mixture setting from a lightly closed position. Yes, the engine will run rough.
If you can bring it above idle from that setting then we know the carb is capable of supplying the needed amount of fuel.
Start bringing the needle in 1/4 turn at a time and let it run for at least 30 seconds between setting changes. Try the throttle each time to see if you are making headway. If you are, keep going until the engine coughs lean or refuses to accelerate again then back the setting up to the last known good setting.
Carb to spark set up would be well worth looking at as well. You should have a mark on the cam that picks up the roller on the carb. Set that to where the roller is picked up at that mark, not sooner or later.
Are you sure you put the gasket/seal around the high speed nozzle? Should seal when the bowl is fastened to the main body.
This should keep you busy for a while.

have you checked the spark plugs during this no run situation ??

porcelain color can tell you a lot about the fuel burning and ignition.
tan, brown, black, clean, oily and WATER droplets . . .
I am NOT a mechanic...... I can only share some of my past experiences with you.

worst case scenario would be water getting into the cylinders.
I just remembered my last episode before I gave the boat to my brother.
I had changed the head gasket twice, new thermostat, new rubber water deflectors,
new side water jacket gaskets.
Then Pappy said it is most likely from the gasket between the motor and lower unit base.
That is when I said enough is enough and gave it to my brother.
hope someone can pinpoint it for you SOON.
Good Luck

Pappy said:

Start your idle mixture setting at a rich 1 1/2 turn mixture setting from a lightly closed position. Yes, the engine will run rough.
If you can bring it above idle from that setting then we know the carb is capable of supplying the needed amount of fuel.
Start bringing the needle in 1/4 turn at a time and let it run for at least 30 seconds between setting changes. Try the throttle each time to see if you are making headway. If you are, keep going until the engine coughs lean or refuses to accelerate again then back the setting up to the last known good setting.
Carb to spark set up would be well worth looking at as well. You should have a mark on the cam that picks up the roller on the carb. Set that to where the roller is picked up at that mark, not sooner or later.
Are you sure you put the gasket/seal around the high speed nozzle? Should seal when the bowl is fastened to the main body.
This should keep you busy for a while.

Click to expand...

How do I adjust the idle mixture setting?

Lugo - you really really NEED to invest in a shop repair manual for your motor.
It will give you indepth information to accurately make adjustments and repairs
to your motor and to do necessary maintenance. It is not a good practice to wait
until something breaks before you find out it should have been addressed in a
preventative maintenance program.

how to clean and overhaul your carb: Johnson carb rebuild
https://www.youtube.com/watch?v=FkhyS83s_XY

parts diagram: https://www.google.com/search?q=25hp+carbreutor+diagram&ie=utf-8&oe=utf-8

The links may or may not be exact for your motor, but will put you in the ball park for understanding the process.
Once you have all the adjustments made to specs, it "should" at least run smooth.
then, you fine tune it from there.
Pappy has 60 years of OMC experience LOL...... he has taught me a LOT and I thought
I knew it all ...







.

Barefoot_Johnny said:

Lugo - you really really NEED to invest in a shop repair manual for your motor.
It will give you indepth information to accurately make adjustments and repairs
to your motor and to do necessary maintenance. It is not a good practice to wait
until something breaks before you find out it should have been addressed in a
preventative maintenance program.

how to clean and overhaul your carb: Johnson carb rebuild
https://www.youtube.com/watch?v=FkhyS83s_XY

parts diagram: https://www.google.com/search?q=25hp+carbreutor+diagram&ie=utf-8&oe=utf-8

The links may or may not be exact for your motor, but will put you in the ball park for understanding the process.
Once you have all the adjustments made to specs, it "should" at least run smooth.
then, you fine tune it from there.
Pappy has 60 years of OMC experience LOL...... he has taught me a LOT and I thought
I knew it all ...







.

Click to expand...

Thank you!

This will keep me busy for tonight, and I'll start looking for a manual for my motor.

This sucks. Prime striper fishing season and I'm missing it.

I pulled the plugs. Both are carbon fouled.

I'm going to guess I am running rich. I'll be playing with the idle air screw on it this afternoon

I got it running!

It was the fuel pump after all.

I figured out that if I kept squeezing on the bulb when the motor would start sputtering, it would keep going.

I took the fuel pump back apart again, and noticed one of the small metal valves was crooked over the hole it was positioned over. I fixed that and put it back together.

Now it stays running, and will go all the way to the top of the throttle with no issues!

I let it sit and idle for about 20 minutes with absolutely no issues.

=D> WAY TO GO DUDE =D>

Now tell me, how rewarding is it to have figured it out for yourself ???
Granted, some of the most simplest of things have kicked our butts
at one time or another.
We learn as we go. Next time you see this question, YOU can chip in YOUR
dos centavos that you have learned from experience !!!!

IF that is your only problem, you should be puttering in the lake Saturday !! LOL

Good Job !!