99 J-150 2 stroke overheat question

[Hingham]

Seems like I have asked a number of questions as of late and I appreciate all of the feedback from you guys. What can I say - I recently became a 1st time owner of a boat.

So here's the background. 1999 Johnson 150. 2 stroke. Oil Injected.

Was out on Monday and the overheat signal sounded after picking up some seaweed. I immediately slowed down, cut the engine and removed seaweed. I restarted the engine and attempted to power up and the signal went off again so I powered down to ~1,500 rpms until signal and red light went off. When I attempted to power up again, engine was shuddering pretty bad - no signal or red light this time. So, I ran the engine at ~1,500 rpms for next 20 mins thinking about the $1G+ bill that was coming my way and then dropped off passengers expecting long run back home. After that the engine ran fine with no shuddering. Ran engine the next again with no problems.

Question is whether that shuddering is normal under overheat conditions when under load or is it a sign of damage from overheating? Or did engine finally cool off and permit normal operating conditions??

Many thanks!

 

[DJ]

Re: 99 J-150 2 stroke overheat question

After any overheat, on those engines, the heads have been stressed. A quick guage is to look at the spark plugs. Any of them real clean? If so, that's where your cylinder head leak occurred.

Retorque the heads to specs and watch it closely. Your spark plugs tell a story. Clean means water ingestion.

 

[Hingham]

Re: 99 J-150 2 stroke overheat question

I'll check them out. But what is with the water injestion? How does water get in there under overheat scenario. Is that bad or just temporarily bad and things adjust back to normal?

Thanks.

 

[Dhadley]

Re: 99 J-150 2 stroke overheat question

When that motor gets hot it goes into SLOW (speed limit overheat warning) and will not go above 2200 or so. You have to shut it off to reset the pack. As long as you run it, it won't go over that rpm and will shudder and shake like crazy.

 

[Hingham]

Re: 99 J-150 2 stroke overheat question

I see. So that shaking is not a sign of some kind of damage but rather restricted rpm operation?

 

[Dhadley]

Re: 99 J-150 2 stroke overheat question

That shaking is the motor trying to tell you something. Once it over heats the rpms are limited. Even after it cools down it won't come out of SLOW until you stop and shut the key off and restart it.

 

[Hingham]

Re: 99 J-150 2 stroke overheat question

Many thanks!