1976 johnson 55hp oil/fuel mixture

[tun1775]

I am running a 1976 55hp Johnson on an old 16ft fiberglass tri-hull fishing boat.

I have a 12 gallon fuel tank and when I add only about 8 ounces of oil (or even less) it runs really slow. Not nearly the power that I think it should have. The boat doesn't even come close to planing out.

Last year when I added fuel to the tank but no oil it ran great and had enough power to plane out the boat. Everything i read says to use a 50:1 ratio. Any thoughts?

 

[Joe Reeves]

Re: 1976 johnson 55hp oil/fuel mixture

That engine demands the 50/1 mixture..... 1 pint (16 ounces) of 50/1 TCW-III oil to 6 gallons of gasoline. Your problem lies elsewhere. The experimenting you're doing will blow the powerhead.

What is the compression of all cylinders?
Will spark (with plugs removed) jump a 7/16" gap?
Have carburetors been cleaned?
Is timer base under the flywheel sticking when throttle is advanced?
S/Plugs should be Champion QL77JC4 plugs, gapped at .040.

 

[OBJ]

Re: 1976 johnson 55hp oil/fuel mixture

tun....you need to be adding at least 32oz of oil to the fuel....that is for 12 gallons (50:1 mix). Your fixin' to burn that engine up if you don't. If you can, get a compression test on the holes....they should be within 10% of each other.

When was the last time the carbs were overhauled? Can you tell if the engine running at the correct temp? Easy way to check this....with the engine at idle and warmed up, you should be able to put your fingers on the flat area at the top of the head for several seconds before having to remove them. If there is no heat, may be some of your problem....cold cylinders don't burn fuel real good. You will know if it's overheating. Spark plugs good? Ignition system good....ie...good spark? How's it idle? What are the rpms at top end? Sorry for all the questions but the more we know, the better we can help.

 

[OBJ]

Re: 1976 johnson 55hp oil/fuel mixture

You type to fast Joe......

 

[tun1775]

Re: 1976 johnson 55hp oil/fuel mixture

The carbs were cleaned two months ago and it has good spark.
Checking the timer base under the flywheel and compression of the cylinders is a little advanced for me. But I'll find someone who knows what they're doing to help. This boat isn't worth putting any money into...