40 HP Johnson will not run above 3000 RPM

[maj_hazard]

Top of the day to you all..

I have a late 80s 40 HP VRO Johnson Outboard. All was running fine when I put her away for the winter. I fogged the engine, drained the gas and changed the lower units oil. This past weekend I put the boat in the water . She started up without issue and I let it idle for 10 minutes to clean out all the winter fog then headed off. The throttle will advance about half way with the expected increase in engine rpm . At this point any further advance in throttle does not affect engine speed as the rpm stays around 3000. If I leave the engine out of gear and advance the fast idle the motor runs above 3000 RPM without issue. So it appears under load is when the problem develops.

Engine appears to idle nicely with no misssing. Fuel is new and shows no water.

Now I'm guility of being at the cottage without my tools so I was unable to really do any troubleshooting including checking the plugs. I did check the cables and linkages and all appear peachie. When the RPMs top out at 3000 the throttle linkages continue to open further as the throttle is advanced.

I'm hoping I have a fouled plug or plugs as I have not changed them since fogging the engine in the fall. With the engine idling smoothly I'm assuming that I've not complely lost a cylindar.

The fuel/oil pump was replaced last spring.

I will replace the plugs and check for free fuel delivery to the pump but outside of that is there anything else I should check for ????

Any thoughts would be apprecaited as I'd like to be as prepared as possible before I head back up to the cottage.

Cheers

Mike

 

[tashasdaddy]

Re: 40 HP Johnson will not run above 3000 RPM

when were the carbs last cleaned and rebuilt?

http://forums.iboats.com/showthread.php?t=244013

 

[maj_hazard]

Re: 40 HP Johnson will not run above 3000 RPM

Carbs where cleaned and rebuilt last summer when the fuel\oil pump was replaced... I was thinking that it could be the high speed jets but on both carbs ????

I guess stranger things have happened...

Thanks for answering..

Cheers

Mike

 

[maj_hazard]

Re: 40 HP Johnson will not run above 3000 RPM

Hey Tashadaddy..

Many thanks, your suggestion was bang on...

Got up to the cottage and started going over the engine.
Checked for kinked fuel lines, confirmed good spark on both cylindars and checked compression 150 for both btw. Refused to believe the carbs needed cleaning as I thought I did a great job last summer rebuilding them.

Gave in , swallowed my pride and took the carbs off. Found nothing exciting on the upper carb but gave it a few shots of carb cleaner and compressed air. Took the lower carb apart and found evidence of water in the bowl (corrosion) as well as something that almost looked like clear uncured silicon all over the bottom of the bowl. Cleaned out the bowl and removed the high speed jet and cleaned the passage out. Got it all back together, launched and blammo everything works.. That was the good news...Then I snapped off about 80% of the lower unit skeg taking the boat out of the water.... Groan...

So first things first... Many thanks for your suggestion as without it my ego would have never let me check the carbs..

Besides a higher risk of prop strikes is there a problem with me running the motor with a good portion of the skeg missing ?????

THanks

Mike

 

[The-Machinist]

Re: 40 HP Johnson will not run above 3000 RPM

You shouldnt notice much change in performance, other than possibily a new desire to wander a bit. Stainless steel skeg guard type prouducts are available that may cover the missing portion, and effectivly solve the problem. Depends on how bad you broke her.....