1985 Johnson 90 port bank cylinders running hot

[baltra]

After rebuilding Powerhead and replacing thermostats (which were corroded/stuck) and water pump, now the port bank cylinders run hot to the touch when idling but stardboard bank cylinders run warm. Tell-tale is peeing strong when in test tank. How can I check if water is running around port cylinder heads?

 

[Haffiman]

Re: 1985 Johnson 90 port bank cylinders running hot

Did you replace water deflectors during re-build?

 

[baltra]

Re: 1985 Johnson 90 port bank cylinders running hot

Thanks for the prompt.....almost instant reply! I did not replace them, but checked for correct functionality and positioning, what are your thoughts?

 

[Haffiman]

Re: 1985 Johnson 90 port bank cylinders running hot

If you got enough water pressure, it may only be caused by circulation 'error' or exhaust leak into the cooling system.
Circulation might be deflectors or thermostats (try switching thermostats from one side to the other).
Exhaust leak might be a defective gasket or crack.
What was the reason for the re-build?
Did you find whatever caused the need for a re-build?

 

[emdsapmgr]

Re: 1985 Johnson 90 port bank cylinders running hot

The strong telltale shows the impeller is functioning-not that the powerhead won't overheat. To check for water flow, run the engine on the garden hose. Pull the large water hose off the port side of the thermostat housing. You should have water flow from the hose. If so, then something is not functioning internal to the thermostat housing and it's blocking water from exiting that side of the block. If you have little water flow from the hose, you have a restriction upstream, maybe in the port head. You may want to pull the head cover off and inspect. I'd borrow/rent a laser temp gun to check the actual head temps while running. Compare them with normal temps of 143-150.

 

[durban]

Re: 1985 Johnson 90 port bank cylinders running hot

i had the same problem with my m8t motor , the corrosion was so bad from salt it ate the aluminum insulation around the bottom sleeve away in some places around the diameter , so i took the deflectors out & through them in the bin , cleaned up the inside with my Nitric Acid formula , reassembled stared & let it idle for over 1 hour , took the rubber pipe off the bottom as well to check water flow , will put it in the water & then do final tests , if it don't work , then i go plan B

 

[Haffiman]

Re: 1985 Johnson 90 port bank cylinders running hot

Durban: We try to keep a rule on the board: Give advice according to the book!
We recommend people to buy the OEM service manual, to check the parts catalog and stay with factory specs.
You may feel safe down in NZ for US lawyers, but one never knows.
You have your 'private' ideas, ok, but keep them 'private' and please do not endanger other than your m8t's' engines.
I strictly advice against DURBAN's proposal about removing the deflectors! They have been there for decades, been working for decades and will hopefully stay in the engines they were originally fitted into for some more decades.

 

[baltra]

Re: 1985 Johnson 90 port bank cylinders running hot

Ok, so this is what I found out....I pulled the water hose off the port side of the thermostat housing, water DOES flow from the hose (so there IS water running around - and refrigerating- the port cylinders), so I ran the engine for several seconds, say 20 or 30?, with the water coming out of the port bank and into the test tank, bypassing the thermostat housing, but the port cylinders were still hot to the touch after these 30 seconds, while the starboard side was barely warm!
Any ideas? I am a "little" lost here.....

 

[Haffiman]

Re: 1985 Johnson 90 port bank cylinders running hot

Quite sure the 'hot' side is the problem and not the cold side ?
Any difference in plug colors?
Buy an IR temp gun and get exact values.
Idle temp should be around 150F.

 

[baltra]

Re: 1985 Johnson 90 port bank cylinders running hot

Oh well, just made me wonder if the very rough idling means that only port cylinders are firing? Will get IR temp gun and check. BTW, what plug are you referring to?

 

[Haffiman]

Re: 1985 Johnson 90 port bank cylinders running hot

Oh well, just made me wonder if the very rough idling means that only port cylinders are firing? Will get IR temp gun and check. BTW, what plug are you referring to?

Spark plugs are the best indicators when it comes to engine internal condition.

 

[baltra]

Re: 1985 Johnson 90 port bank cylinders running hot

I need to thank haffiman and emdsapmgr for their suggestions and contribution to resolve this issue. Turned out the water was flowing normally and the pump and thermostats were operating correctly, but only the port cylinders were firing. I found out the starboard power pack was bad. I replaced it and now the temp on all cylinders is around 150F and engine is running good. Good job guys! Thanks.