1957 Johnson 35hp overheating

[diveboss]

I have the unique situation where I have twin ‘57. 35hp on the same boat, so am constantly tuning them to be sync’d as good as possible. When recomissioning this spring and running the motors in a barrel, I noticed the port motor was not pushing much water out the exhaust, so became suspicious of the impeller. Took the lower unit off to inspect the impeller and everything looked fine (I did impellers on both motors 2020). blew air up through the power head and it seemed to blow through fine. Made sure both water intake screens/area were clean and blew out with high air pressure. All seemed good, so reassembled and went for a sea trial. Water seemed to be coming out the exhaust, but not nearly the same as the STBD. Motor. Engines both ran perfectly, but the port motor was significantly hotter. If I put my hand into the water exhaust, the STBD. Motor is pretty warm, but Port motor is HOT.
brought her back in and lifted engine covers on both. STBD motor powerhead is warm to the touch, but the port side engine powerhead is HOT!
During the entire sea trial, both motors ran perfectly, idle, full power, etc.
what is going on, possibly powerhead gasket?

 

[Crosbyman]

have you ever pulled the cyl head to check the water passages to see if all crudded up ...being a salty .

was trying to find the thermostat in the past list but 57 may not have one ???

 

[diveboss]

I have not pulled the cylinder head, but thinking that may be the next step?
Just trying to avoid that, but need to figure this out before something goes boom. As mentioned, I did blow air through everything when checking the impeller and it seemed to pass through fine. The boat only sees fresh water, so shouldn't have salt build up, but still could be crud in there.
The 57 does not have a thermostat, so that is out.

 

[jimmbo]

You might have to pull the Waterjacket Covers off the Head, the one over the Exhaust Ports , and even the Powerhead off and check for blockage(s).
However, first take another look at the Water Pump. Any Scoring of the Housing, and the Plate? Is the Grommet that seals the Pipe to the Pump in good condition? Is the Pipe intact all the way up, and is it connected and sealed to the bottom of the Powerhead? Also check that the Water Passages in the Lower unit are Clear and the the Water Inlet behind the Prop has its plug in place, and is sealed

 

[Crosbyman]

During the entire sea trial....land locked ocean I guess

 

[diveboss]

What do they call test rides if not Sea trial? Lake trial? Lol
I hate to check that impeller again as I’ve done quite a few, but thinking I will double check it as that is the easiest. First will check that plug behind the propeller, but not sure if that would matter as it ran hot in the barrel with no prop turning. Pulling off water jacket and cover over exhaust looks to be a big job? Need to remove lower cowl to get access to some of the lower screws? looks like I will need new water jacket gasket and exhaust cover gaskets (2) for that. Plus gaskets for the 2 smaller covers that go over water jacket? Looks like all those screws are for the water jacket covers and all the bolts are for the head gasket? Is there any specific sequence on putting all those screws back in? Guess I’m getting ahead of myself.

 

[diveboss]

Checked the water inlet behind the prop and the plug is in place and sealed.
I will put the lower unit apart this weekend and have another look at the impeller. Is there any good way of doing a water pressure test to see if there are any restrictions while I have it apart?

 

[Crosbyman]

if you wish you can check the cavity below the water pump to make certain no accumulated deposits are causing water flow into the pump itself.

 

[jimmbo]

The Impeller is only one of the Wear Items that make up the Waterpump, the Housing and the Plate below the Impeller are subject to wear too

 

[3rdtimesthecharm]

I had a worn lower plate once. Wouldn’t pump even with a new impeller.