1978 Johnson 85HP

[Billabong089]

Hey guys,

Having a strange problem, It runs fine out of the water on muffs, throttles no problem, all cylinders have spark, like it runs absolutly fine out of water.

Put it in water and just goes barely above no-wake speed, no power.

Any suggestions?

Simply put, runs fine out of water, in water, wont gain speed, wont go any faster than no-wake speed

plugs are new, just replaced.

 

[HighTrim]

Re: 1978 Johnson 85HP

Welcome to iboats.

Will the spark jump a good 7/16" gap with a bright blue ZAP!!? on all cylinders?

Does the motor rev up but not accelerate?

You're not dragging your anchor or trailer are you ?

 

[Billabong089]

Re: 1978 Johnson 85HP

lol , the spark does look good, what do you think the most common cause of this is?

I think maybe some kind of fuel issue... but IDK, I winterized it and it was running fine before, then the first time out of this season and its acting up like this...

Pretty much I push the throttle down, it speeds up a little bit, slightly faster than a no-wake type speed, but it wont pick up any speed, I just dont understand it!

Please help! I dont want to play a money guessing game =/

 

[321lawncare]

Re: 1978 Johnson 85HP

jets in the carbs need cleaned or rebuilt !

 

[Billabong089]

Re: 1978 Johnson 85HP

how do you know that? How do I go about cleaning it, is it difficult to rebuild the carbs? I really don't have any experience with Carbs but I'm fairly good with engines and cars.

 

[75-JOHNSON]

Re: 1978 Johnson 85HP

do you have any fuel additive in it? I was trying to break in my new engine so i mixed the fuel slightly rich, and added LUCAS fuel treatment (which later i found out is just basically oil) and ended up with the same problem. mixed up a fresh mixture of just gasoline and oil (a bit lean) and works good now... just an idea..

 

[Chinewalker]

Re: 1978 Johnson 85HP

We don't "know" that, but we have a hunch the carbs are the problem. You say you have spark. We can assume (to a degree) that you have compression as it ran fine when put away. Although it wouldn't be a bad idea to check compression while you're at it.
Your motor has, essentially, four carburetors, set up as two 2-barrel carbs. If any one of them is gummed up, the cylinder it is feeding will not run and will also be starved of lubrication (so don't run it again until you've either fixed it or eliminated it as a possibility).

Carbs must come off to be cleaned. Good idea to install new carb kits while you're at it, too, as they will have ethanol resistant gaskets and bits.