'81 Johnson 90 intermittent power loss

[metriccrescentwrench]

1981 Johnson 90 HP. This engine runs flawlessly ALMOST all the time. Last compression check: 120 118 115 115. I put new spark plugs in 2 weeks ago.

Every so often when going slow (no wake speed) there will be an obvious drop in power (but yet it doesn't really run rough), then when I feed in throttle there will be very poor acceleration for maybe 10 seconds and then WHAM, it'll jerk your head back when it starts running on all cylinders again. This hasn't happened often, maybe 3 or 4 times in the past 6 months. The latest occurence was this past weekend, while idling away from the boat ramp. As has always been the case, after the one hiccup it ran great for the rest of an afternoon of pulling skiers and tubes.

Am I barking up the wrong tree in assuming this is an ignition related problem? Maybe a power pack?

I hate intermittent problems because it always seems like you end up throwing money away until you finally luck into the fix.

 

[tashasdaddy]

Re: '81 Johnson 90 intermittent power loss

you probably have a jet that is clogging, and clearing out. or the timing plate is sticking, and coming free.

 

[metriccrescentwrench]

Re: '81 Johnson 90 intermittent power loss

Thanks for the input. I'm trying to reconcile these potential conditions to my observations.

Could a sticky timing plate cause a loss of power while operating at a constant throttle setting in a no wake zone? I could see that once throttle is fed in to accelerate, but am wondering if that could cause what I saw.

I hadn't thought about the possibility of a jet clogging, I suppose that could possibly account for the symptoms. I'm wondering, if that is indeed the problem, what could cause that because I replaced the fuel line and installed a spin-on fuel filter a little over a year ago (replaced the filter cartridge this spring). Are we talking about a carburetor cleaning/rebuild?

thanks again.