'63 75Hp Johnson Slow and Sucking Gas

[jimmbo]

Re: '63 75Hp Johnson Slow and Sucking Gas

Those old OMC V4s were very thirsty, burning a lot of gas at WOT. At idle they are still just about as thirsty.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Definitely not a fuel flow issue, it sucks gas like a son of a gun.

I put in some ethanol free gas tonight and seafoam and it ran better for sure, but still not as good as it could be... took quite some time to pick up speed. Is it possible that I have a stuck valve or something?

 

[jimmbo]

Re: '63 75Hp Johnson Slow and Sucking Gas

Which prop is on it? There are only about 3 to choose from for the last 40 yrs

10 x 9 1/4
10 x 11
10 x 12

 

[82rude]

Re: '63 75Hp Johnson Slow and Sucking Gas

the fact that it takes a while to hit good speed and sometimes not at all could also be a spun hub.i had one on a Nissan years ago that acted just like your motor.sometimes good most times no.is it hitting recommended rpm and still not picking up speed ?also theres a possibility of coil breakdown.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Not sure which prop is on it. How do I tell? (boat is docked)

It isn't hitting high rpm's, and when it does it picks up, so I don't think its a spun hub. How do I test the coil?

 

[jimmbo]

Re: '63 75Hp Johnson Slow and Sucking Gas

You'd have to take the prop off. The info should be on one of the ends of the hub. Or with the 10 x 9 1/4, well it might be 9 1/2, the info was on one of the blades

 

[fromcarsToboats]

Re: '63 75Hp Johnson Slow and Sucking Gas

Really sounds like your losing a cylinder. Is it idling good? Are you still running with the choke on?

 

[Willyclay]

Re: '63 75Hp Johnson Slow and Sucking Gas

Its an 18ft tri hull bow rider.

That is a lot of boat for only 75HP and tri-hulls are typically heavier than a conventional hull of equal size. Also, have you checked the bilge for water-saturated flotation foam which would add more weight? I feel your pain because I had the 1962 version of that motor and battled that hot-water choke for many years. My only suggestion is to compare the cost of fuel consumption of that old beauty to the purchase price of a more fuel efficient, newer motor. My decision was to keep feeding the beast. Good luck!

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

However, none of this matters now because the engine wont stay in gear. God dammit....

See this thread if you have any ideas:
http://forums.iboats.com/johnson-evinrude-outboards/1963-johnson-slipping-out-gear-619297.html#post4314409

Thanks guys.