1988 Johnson 90hp (overheating)

[scottygethotty]

Hi

1st off I want to thank everyone who helped me with the planing on my boat.

I changed the plugs, fuel line and two leads on the spark plugs where the wrong way round.

The boats scarily fast.. wow


Thanks

Now i have a new problem, when I opened up the throttle the boat started to plane for about a minute on around 80% of its power and I saw the temperature gauge needle start rising then the alarm went off and the engine shut down.

Previously, I changed the impeller only but last week so its not the bottom unit.

I spoke to a boat mechanic, he said its probably the thermostats.

Could it be anything else? and how hard is it to do the job myself?


Thanks

 

[rndn]

Re: 1988 Johnson 90hp (overheating)

Without a history, is it possible the engine water intake is out of the water when your boat is on plane?

 

[scottygethotty]

Re: 1988 Johnson 90hp (overheating)

thats possible, never thought of that!

whats the answer then as i cant do anything about that can I,

 

[bktheking]

Re: 1988 Johnson 90hp (overheating)

Take a side pic of the motor and transom and post it.

 

[rndn]

Re: 1988 Johnson 90hp (overheating)

thats possible, never thought of that!

whats the answer then as i cant do anything about that can I,

Take the picture as requested above, and yes there is something you can do about it.

 

[scottygethotty]

Re: 1988 Johnson 90hp (overheating)

Hi

Please excuse my boat its, my first and its on a budget..

 

[bktheking]

Re: 1988 Johnson 90hp (overheating)

Looks good to me, pull the stat cover and check the stats out in boiling water, they may be bad.

 

[scottygethotty]

Re: 1988 Johnson 90hp (overheating)

Stats??? ohh thermostats ok what does a bad one look like?? and how will i tell in boiling water?

 

[bktheking]

Re: 1988 Johnson 90hp (overheating)

The stat itself will open at around 140F, use a pot and a strainer to hold the stat and a thermometer.

 

[scottygethotty]

Re: 1988 Johnson 90hp (overheating)

I took a look the cover off and looked at where the water was pumped from round the head, there are 2 hoses that pump water round i guess 1 hose for 2 heads and the same on the other 2 heads.

I found one of the pipes had a kink init. and when i took the hose off it half of it was blocked with salt deposits.

hopefully this will do the job before i start on the thermostats...

will post the results....

thanks

 

[kenskat1]

Re: 1988 Johnson 90hp (overheating)

Had the same problem. Changed thermostats/water pump this helped alot. My biggest problem was sand/salt behind the water jackets. I would remove them and check for sand/salt.
http://forums.iboats.com/album.php?albumid=87

 

[AEROCOOK]

Re: 1988 Johnson 90hp (overheating)

I took a look the cover off and looked at where the water was pumped from round the head, there are 2 hoses that pump water round i guess 1 hose for 2 heads and the same on the other 2 heads.

I found one of the pipes had a kink init. and when i took the hose off it half of it was blocked with salt deposits.

hopefully this will do the job before i start on the thermostats...

will post the results....

thanks

Good chance you will see an improvement but if you found heavy salt deposits in the hose it's likely that there are other deposits internally as well. If it were mine I would still replace the thermostats as a precaution and as a matter of routine maintenance. I dont think the 90 hp was a bubble back in 1988 which means changing the thermostats is a whole lot easier than if it were a bubble back. My 1988 110 is a bubble back and I will be doing this job on the weekend, not looking forward to it.

 

[bktheking]

Re: 1988 Johnson 90hp (overheating)

If I were you, pull the stats and use a product like salt away to flush out the entire motor, like everyone else said, salt is probably everywhere else if you found it in the hose. Once you flush the salt out put the stats in and it shouldn't overheat anymore. Being a salt water motor puts a spin on the issue.

 

[scottygethotty]

Re: 1988 Johnson 90hp (overheating)

ok, I will get some salt away for it. I know I have to flush the engine with salt away twice and leave for 24hours.

Does it help using hot water? and do i really really have to take the thermostats out, isn't that a big job?

Thanks all you guys

 

[bktheking]

Re: 1988 Johnson 90hp (overheating)

I would, they could be the issue, unless you know they are new and functioning.

 

[keylargo52]

Re: 1988 Johnson 90hp (overheating)

How did the salt-away work for you?
Just started using it on my 1990 Johnson 200 yesterday...will use every day for 6 days then test the engine out on the lake