87 Johnson 88 HP Overheating Problem

jerryny

Seaman Apprentice
Joined
Sep 13, 2012
Messages
37
Help please. I am out of ideas. I have an 87 Johnson 88 HP SPL motor. The 2 cylinders on the Starboard side of the motor are running 20 to 25 degrees higher than the bank on the port side. I did the following w/o any good results:

- I moved the power pack and coils from the port side to the starboard
side. No Help

- The water pump has been rebuilt. no Help

- I took the thermostats out. No help

- I removed the hoses from both sides and observed that both banks
had water coming out while the engine was running. I also hooked a
hose to to one side of the powerhead and when I turned the water on
it came out the came out of the other side plus the pee hole.

So I am assuming that water is circulating thru the head. Am I missing anything? I don't know what to look at next. What else could cause both cylinders on the starboard side to run so much hotter.

I forgot to mention that I am running 89 octane with a 50:1 mixture.
I was using an infrared digital meter to measure the temps.

All help is greatly appreciated.
Jerry
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 87 Johnson 88 HP Overheating Problem

There is water moving through the passages but you could have a blockage in the water passage on that side. If remove the head take a nice stiff wire and run it through the water passages to at least break it loose. After that you should be able to put it in a barrel and crank the engine to flush the crud out. Make sure you put a new head gasket on and torque it down properly. Also, make sure that after running it for five or six hours you retorque it because they will loosen up. Also you only need to run 87 octane in it as they were made to run on that. Did you test your tstats in a pan of hot water? You could have a bad one but they don't fail that often.
 

jerryny

Seaman Apprentice
Joined
Sep 13, 2012
Messages
37
Re: 87 Johnson 88 HP Overheating Problem

There is water moving through the passages but you could have a blockage in the water passage on that side. If remove the head take a nice stiff wire and run it through the water passages to at least break it loose. After that you should be able to put it in a barrel and crank the engine to flush the crud out. Make sure you put a new head gasket on and torque it down properly. Also, make sure that after running it for five or six hours you retorque it because they will loosen up. Also you only need to run 87 octane in it as they were made to run on that. Did you test your tstats in a pan of hot water? You could have a bad one but they don't fail that often.


Yes I verified yhat the tstats are opening and closing properly. Today I was looking at the water exits from the tstat housing and down the lower half of engine. On the port side I was able to put a piece of weed whacker line in w/o any problem. However on the starboard side there seems to be some type of of obstruction. From what I can see(you don't get much viewing area) it almost looks like a chunk of something in the hole. It doesn't want to come out. Makes me think that maybe its a chunk of metal. Not sure how something like that would get in there. Any ideas on how to proceed.

Thanks for your response
Jerry
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 87 Johnson 88 HP Overheating Problem

The warmed block water exits the powerhead though the two large hoses that go to the thermostat housing. The thermostat housing dumps into the rear of the exhaust adapter, then down the midsection. Any chance you can post a picture of the area that you think is restricted?
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 87 Johnson 88 HP Overheating Problem

Have you had the cyl head off of the stbd side and checked the water deflectors for being swelled up??
 

jerryny

Seaman Apprentice
Joined
Sep 13, 2012
Messages
37
Re: 87 Johnson 88 HP Overheating Problem

The warmed block water exits the powerhead though the two large hoses that go to the thermostat housing. The thermostat housing dumps into the rear of the exhaust adapter, then down the midsection. Any chance you can post a picture of the area that you think is restricted?

My mistake. I was comparing the way the flow into the rear of the exhaust adapter on the port side to the starboard side.
The starboard side makes a 90 degree downward turn not to far from the opening. When I was looking at it(which is hard as there ain't much room) what I was actually seeing was the back wall. The port side exit goes in much farther.

I included some pictures of the water deflectors and cylinder head.

I have also removed the inner and outer exhaust covers.

I am wondering where I can try and back flush both the cylinder and exhaust passages either with compressed air or water. I really don't want to drop the lower unit unless I absolutely have to. The water pump is new so I'm not suspecting that is causing the starboard bank to overheat. Of course I could be wrong.

Any suggestions would be greatly appreciated and welcomed.
Jerry
 

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jerryny

Seaman Apprentice
Joined
Sep 13, 2012
Messages
37
Re: 87 Johnson 88 HP Overheating Problem

Update to my starboard side overheating problem. I decided to pull the port side cylinder also. I've attached a picture of what it looked like underneath the cylinder head cover's gasket. I think all that white gunk is gasket sealing compound? No water circulates under there does it??

Also on the cylinder head gasket there is a tiny hole at the top and bottom of the gasket. Is this where the water enters the cylinder head water jacket? Seems to be such a small hole considering the size of the inlet holes on the block side.

Again a million thanks for all the help.
Jerry
 

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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 87 Johnson 88 HP Overheating Problem

Water diverters.jpgYour deflectors (seem to look ok) should go back in the block strategically. See pic for normal installation.
 
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