Engine was running great, until it wasnt.. Carb issue?

Shadow91

Petty Officer 3rd Class
Joined
May 1, 2017
Messages
97
Okay so as many of you know ive been trying to get my old OMC 2.5 going for some time now. After finally getting the engine to run without overheating I finally got to take it out to the lake. Get there, drop the boat in the water and after some small convincing it fires up and runs okay. It wants to idle but if i give it any gas at all it dies. I assumed maybe just being a cold carb still After letting it warm up for awhile I was able to put it i gear and move away from the shore some. Still it would get to about 1000 rpms, pop and die, or pop and almost die until it actually died. After just slowly giving it throttle it would eventually just clear up and rev no issue. Full throttle and away we went. The engine roared up to about 4000rpms and hopped right up on plane. Engine was running fantastic, oil pressure was great, engine temp was just under 175 on my gauge. Ran for a good 30 minutes WOT to try and really let the engine get nice and warm and open up. Went threw about 1/2 tank of gas with varying throttle from 2-4000 rpms no issue. Slow down to in idle and it just dies. After some convincing it fired back u and didnt want to idle. Finally got it in gear and it again just wanted to pop and dies right around 1000 rpms. I could sit there and hold it just at about 1000rpms for awhile then all the sudden would feel it 'open up' and the rpms would raise to about 1200. At the point i could open the throttle no issue. Did that for the rest of the day just working the throttle at an idle until i could get it above 1200 rpms and it ran just as good as i could hope for. Even pulled a tube with some friends doing that. Idle was a complete pain in the butt but with just working the idle it would constantly stall out and die. Never could get it to idle without dying after just a few minutes. I assumed I just had a sticky choke or plugged/partially plugged idle jet.

Well then we pull up to a beach and let the kids have some fun on the sand for awhile. We are there for maybe 45 minutes or so, go back to the boat and fire it up. Engine DID NOT want to fire. Finally after some starting fluid (i had no other choice) it fired and would only idle at about 900 rpms with the throttle half open. If i moved the throttle ether way it would die. Finally I just had to get back to the ramp as it was getting dark so i put it in gear and idled it back to the ramp. While running back to the ramp, regardless of my throttle position it would not change speeds. I could be WOT, 1/2 throttle or just enough pressure to put in gear, I got a solid 750-900 rpms. No matter what. It dld great, best it had all day, but that was all, an idle.

All in all i ran probably 10 gallons of fuel threw it, with probably 1/2 of that being old gas with just treatment in it.

Im thinking I either have a fuel supply issue (is there a filter in the fuel pump??) or something is way messed up on the carb. I just have so little experiences with carburetors that im just not sure. I could rebuild the carb if thats what needed or look into an entire different issue if anyone thinks im looking at the wrong area.

And any recommendations for a carb rebuild kit for this old 2.5?

Thank you for any and all help
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
50,283
OMC used a few different carbs. so start with the factory OMC manual (Not a Seloc, Clymers or Chilton)
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,335
That Rochester is easy to rebuild . The check ball in the bottom of the acellerator piston bore is surely stuck and the piston seal is dried up and shrunken. If the float bowl has white residue from water the best way to clean it is with some Muratic acid or bead blast it. Regulator carberator cleaner may help if it is gummed up from dried gas .
 

Shadow91

Petty Officer 3rd Class
Joined
May 1, 2017
Messages
97
Well damn. I'm so pissed off right now that I missed this weeks ago with the engine out of the boat. I seriously looked all over and at the time had no water in oil..but I guess that's because it was going out faster then it could come in. Damn block is cracked.

sBhlKof.jpg


From you all that have been in my shoes. What should I do?

Keep looking for a replacement used for hopefully cheap? Buy brand new? Or sell boat for cheap and start over from the beginning? I'm just so frustrated right now I want to burn the damn thing down. Ugh.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,592
Depends on how much you like the boat. Cannot get a new 2.5 but might be able to find a used or reman
 
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