Power comes and goes?

[thresher15]

1996 Johnson Ocean Runner 150 carbed.

Took the boat out yesterday for some early morning striper fishing. Got to the boat around 6 am, temp about 26*, plenty of frost on the boat. Idled out of the marina then got up on plane and ran at about 4200 rpm's for about a mile and a half. Then, all of a sudden the motor loses power and comes off plane and I kill the ignition. Check the lower unit and everything is fine, nothing in the prop. Starts right back up like nothing happened so off we go again for about 3 or 4 hundred yards at speed and it happens again, falls off plane and powers down. Starts back up but this time it is running rougher and lacks power so I started idling back in (didn't want to try to get on plane and damage it). Halfway back in the roughness smoothes out and it's running fine again (ran just like nothing ever happened, smooth as can be) so I get on plane and take it back to the slip. I am going to pull the boat out today.

Couple things of note: each time it lost power the fuel bulb was softer than normal. Second, I took the cowling off to look around and noted that the starboard side bank of cylinders was hot to the touch but the port side was cool to the touch and nothing else was out of the ordinary. Third, there is an in-line fuel flter that i have not been able to take off yet (didn't have strap wrench on the boat).

 

[jonesg]

Re: Power comes and goes?

Just guessing, wait to see what the experts say,

I have a 94 J150, similar carbed.

its overheating, check the overheat switch.
Overheat alarm shoulda sounded, ground single wire from heat switch (brown wire) to block, horn should sound.
Its falling into slo-mode then rpm picks up again as the engine cools and slo turns off. Sounds like fuel supply.

 

[tashasdaddy]

Re: Power comes and goes?

there are several possibilities, running hot, the slow mode kicks in, only allowing 2000-2500 rpms. power pack failing on one bank of cylinders. fuel restriction.

http://www.outboardbooks.com/
time for an OEM Service manual, and start trouble shooting. do not get a Seloc or Clymer manual.

 

[thresher15]

Re: Power comes and goes?

Hmm, my very first thought was fuel restriction due to cold temps/ice or just general condition of the gas, but when I felt the cold bank of cylinders I thought bingo, bad powerpack. Would the alarm sound for a fuel restriction? It does have the slow warning system. No alarms ever sounded. The engine did idle rough and I imagined this was due to running on 1 bank of cylinders. I have a Seloc manual; no good? I will take a look at the link for the OEM manual, I'm sure there is no substitute for OEM.

 

[Randybeall]

Re: Power comes and goes?

I would first suspect carb Ice. Need to drain the float bowls and perhaps even clean the carbs. A tiny bit of moisture in the fuel can freeze solid in the fuel passages and raise havoc with the running. A bottle of anti water additive in the fuel might be a good prevenative. When you are running at speed the air going through the venturi of the carburator causes a tempature drop and the body of a carburator can be 10 to 20 degrees colder than the surrounding air depending on the relative humidity. Old VWs suffered from this regularly.

 

[Benny1963]

Re: Power comes and goes?

could be fuel .electrical ,or overheat .
your gona have to go thru the proper steps use oem manual and start there do you have inboard tank ?may run external .would check head temps wtih gun and fix the possible overheat first,then on to carbs compression and soforth,slowly test it does it pickup if ya pump the ball

 

[thresher15]

Re: Power comes and goes?

Quick update: I was able to take it out for a 10 mile spin last night and could not duplicate the problem?? Temps at the time were in the low 50's. Not sure now wether to pull it or not since I really don't know what the problem is. I'm thinking a power pack/stator about to go or else it was carb ice/fuekl issues.

Can anyone tell me if the warning horn will sound for a fuel restriction?

 

[Chris1956]

Re: Power comes and goes?

My '98 Johnny 150 has a vacuum sensor on the left side of the fuel pump that indicates fuel restriction. All the sensor wires for the System Check are tan with a tracer. This wire should be tan/orange. Disconnect from the vacuum sensor and ground the tan/orange lead, ignition on, to test it.