1984 OMC will not run full power with cowling on.

[Tomb77]

I put this in other outboards but the OMC is the same thing as johnson so looking for help.

I have a 1984 OMC seadrive out board 1.6L. I got the boat this spring and was in running condition but the engine ran poor. Purchased a manual and went through everything I could think of and got it running good made several trips in the Atlantic around 30 mile out. Then about a month ago we went out and about 5 mile into the trip the motor started to bogie down would only get up to about ? rmp. Pulled the cowling off and check around and could not find any problem started out again and the same thing could only get ? speed. Took the cowling off and ran without it to look around and got full speed ran better than ever. This one has me stumped there is no problem with air flow I can see but the motor will just not run with the cowling on. There are no cables or wires pinched and it will run great with the muffler on in the drive way I know that does not mean anything. The idle is good starts up good just won?t run full speed with the cowling on. The motor seam good and sound everything works tilt and trim cables wire over temp warning no problems. Top end was redone 2 years ago and I mix my fuel 50 to 1. Any one got a subjection.

 

[coolguy147]

Re: 1984 OMC will not run full power with cowling on.

exhaust leak?

 

[Daviet]

Re: 1984 OMC will not run full power with cowling on.

If an outboard has a blown base gasket, it will allow exhaust into cowling and starve engine for fresh air. This usually gets worst with high RPM. Get a can of aerisol fogging oil and spray into carbs and look for smoke coming from around base gasket.

 

[blue_streak]

Re: 1984 OMC will not run full power with cowling on.

might want to check for a pinched/grounding wire where the cowl goes onto the motor.

just a thought

 

[emdsapmgr]

Re: 1984 OMC will not run full power with cowling on.

Check the air vents in the cowling. Could be something is restricting airflow to the carbs, reducing their ability to make hp.

 

[kenmyfam]

Re: 1984 OMC will not run full power with cowling on.

Exhaust leak or air intake restriction by the sounds of it. Other could be a plug wire or two grounding out on the cover when it is in place.

 

[crxess]

Re: 1984 OMC will not run full power with cowling on.

Tossing my vote in for exhaust leak or short when installing cowl. Main suspect - exhaust leak

 

[Faztbullet]

Re: 1984 OMC will not run full power with cowling on.

Yep, sounds like exhaust leak from base gasket or bolts on exhaust plate. When you check engine with fogging oil make sure its in water or trash can so exhaust has back pressure to force it out leaking area.

 

[ShawnN]

Re: 1984 OMC will not run full power with cowling on.

insulation on the cowl lose being sucked into the intake ?

 

[Tomb77]

Re: 1984 OMC will not run full power with cowling on.

Update: First thanks for the help. Found 2 possible. There was some of the foam insulation lose so took all of that off. Second the studs on the back of motor one striped on had no nut. Was able to get a nut on the one and tightened down. Finley got out yesterday for the first time in a while. Ran good fished all day made several 6 mile moves water a rough for the sound but still a nice day a few blues no big drum this time. I should pull the power head and replace the studs but not right now. The motor is running well right now. I want to restore the boat and put on a bracket with a 150 or 175 Yamaha or Honda. But that will have to wait for better times.