Half power on 1979 Johnson 85hp outboard

[fmbellok]

Boat was running great for about 20 minutes when in the middle of towing my son on a tube, the engine lost about half of its power. Thought it might be a fuel issue. Switched from the old metal tank to the new tank, but no difference. I thought I heard air when I pumped the gas hose. It was very old, so I replaced, but again there was no difference. I also wonder if there was some dirt in the fuel screen in the fuel pump. Any suggestions?

 

[Yepblaze]

Re: Half power on 1979 Johnson 85hp outboard

Perhaps...... But, Does it still idle well or has the idle dropped off since the incident?<br /><br />If the idle is still fine it could be a fuel filter related problem. Or perhaps a bit of debris has made it's way into the main jet(s).<br /><br />If the idle is off, it will be time to check compression. If that check out ok, then start looking for ignition realeted failure(s).

 

[JB]

Re: Half power on 1979 Johnson 85hp outboard

Howdy, Morgan.<br /><br />Did you try pumping the primer bulb while this was happening?<br /><br />I think it would be useful to determine whether the problem is fuel or fire related before tearing anything apart.<br /><br />Your symptoms sound like you lost a couple of cylinders. You can check that by disabling spark plugs while idling on the muffs. Disabling a dead cylinder will not affect idle, disabling a good one will cause a drop in rpm.<br /><br />Side by side cylinders share a carb, each bank (top & bottom) has it's own powerpak.<br /><br />Let us know what you find.<br />