1988 Johnson 90Hp Overheated now wont plane!!! Please Help

[werdna219]

I was out boating today and on my return trip i slowly started to lose power. When I turned around i saw white smoke and knew the motor was overheating. The motor stalled and I was stranded. After about 10 minutes of floating i decided to try the engine.

It started right up...with a little bit of a hiccup, but nonetheless started.

So i tried to drive home, and the boat will not get on plane!?!

I drove the 2 miles home at 10mph and parked the boat overnight.

What is wrong with my engine?

Did I damage it more by driving home?

Any help would be appreciated. Thanks!

 

[Daviet]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

I would start by doing a compression test.

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

I had one done last summer. The results came back fantastic. The mechanic was impressed with how strong it was.

 

[AEROCOOK]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

Good chance that you have damaged it if you overheated it. I would start with a compression test. (now, after the overheat happened)
Did your overheat alarm go off? do you know if it even works?

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

There was no alarm. So no I dont think that works. There is also no thermostat for the engine temperature on the dash.

 

[AEROCOOK]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

There was no alarm. So no I dont think that works. There is also no thermostat for the engine temperature on the dash.

You can test the alarm function by unpluging the single tan wire that goes into the switch that is pressed into the cylinder head(s) then grounding the harness side (female) to the block. I think the key needs to be in the on position for this test but Im not 100% on that.

 

[nwcove]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

last summer....and this summer, after an overheat, are like apples and oranges. i agree with all the above advice, check the comp numbers. (buy a guage , it might be cheaper ($30 ish) than taking it to a shop). but it does sound like you have issues with your motor.

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

Wouldnt the engine continue to overheat the whole way home? It seemed fine just not up to speed...

 

[AEROCOOK]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

Wouldnt the engine continue to overheat the whole way home? It seemed fine just not up to speed...

Not necessarily. Do like we suggest, start with a compression test, it is the most telling indicator of damage after an over heat.
BTW, where were you seeing all of the white smoke and how are you sure that it overheated?

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

um...Great Point. I just assumed like a car white smoke = overheat. But when I think about it when i start the engine up i see white smoke anyway. Do my symptoms of the boat slowly dying while on plane resemble the reaction to an overheated engine?

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

there was also a burnt smell...

 

[mstahl1171]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

I agree with the above mentioned checks..do the compression check. That will tell alot about the motor condition. Definately check the alarm horn. You may have lost spark on one cylinder...burnt piston..hard to say until you start troubleshooting.

 

[nwcove]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

it probably did run hot on the return trip. with no guage/alarm you cant say. pull the plugs , have a look, post pics. sounds like it leaned out and scored a piston.

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

if one of the pistons stopped working does this explain the loss of power, and the reason why the engine was able to work just not up to speed?

 

[mstahl1171]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

if one of the pistons stopped working does this explain the loss of power, and the reason why the engine was able to work just not up to speed?

Yeppers

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

so best case scenario...cheapest?

Worst case scenario....most expensive?

If its a burnt piston which I am reading now sounds like my symptoms what am I looking at?

 

[werdna219]

Re: 1988 Johnson 90Hp Overheated now wont plane!!! Please Help

For anyone that sees the same symptoms I did last week....have a spark plug tool handy on the boat and check ur plugs. One of mine was extremly rich and fouled. Replaced that now my engine has a new hum to it!