Logo
FULL SITE MENU

1989 OMC 15 HP loosing power, hard starting.

I

icarus

New member
Newbie here, thanks in advance for any and all help.

I have a 1989 Johnson (OMC) 15 hp shortshaft. This motor is in remote bush service in Northern Ontario, Canada. I have owned it since new.

I have had a number of problems of late. For years the motor would quite quickly lose power, and you could restore full power (rpm) by quickly pulling and pushing in the choke. This was solved with a new (used carb)

The new problem(s) are thus. The motor is very hard to start when semi warm, (after sitting ~1/2 hour) I haven't figured out if it needs more choke or is over choked. The second problem is, while running full throttle (full rpm) slowly, almost imperceptibly it begins to drop rpm, until it seems to be running ~80% rpm, and then slowly it comes back to full rpm, only to repeat the process. The final issue is that when the motor is tipped up, the carb drains into the lower cowl, spilling fuel into the water. I know my older (1960's vintage omc's would do that) but I have no memory of this ne doing it until I replaced the carb. My newer vintage omc's don't leak like this.

My hunch is that all three problems are related, but after tearing the carb apart time and again, I am lost for ideas. Anybody out there who has a clue to what is happening?

Thanks in advance,

Icarus
 
Re: '89 OMC 15 HP loosing power, hard starting.

Don't get impatient, this is a forum not a chat room.
It sounds like you have a carb problem. Part of the problem sounds like the float is set to high or the needle and seat is not shutting off the fuel properly. It also sounds like the high speed jet is particaly blocked and causing your high speed problem. If it were mine I would remove the carb and rebuild it paying attention to the needle and seat and make sure the high speed jet is clean.
 
Re: '89 OMC 15 HP loosing power, hard starting.

Daviet,

Thank you for your reply. (Sorry if I seem impatient, since I am new to this forum, I have no idea how active it is, so I was curious to keep the newbie thread near the top,, probably not a good idea).

I too concur that it is a carb problem. I have had it apart a number of times, and can't seem to find any real issue. This motor is in daily bush service, so it's supply of parts is mostly bone yard parts from other OBs. Perhaps this winter I will tear it down, and rebuild the carb with a new kit.

Once again thanks for you help, and any future help!

Tony

PS. What is a good way of measuring float height?
 
Re: '89 OMC 15 HP loosing power, hard starting.

Rule of thumb is to turn the carb upside down and the float should be parallel to the carb body. You should check the manual to be sure.
 
Back
Top