Thermostat on 235 Evinrude

jimmbo

Supreme Mariner
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May 24, 2004
Messages
13,021
Pressure Relief Valve. Allows more cooling water to flow at higher rpms, and less at lower ones.
Thermostat might be a little too small to permit enough flow to meet cooling requirements when engine is warm and running fast
 

oildriver

Cadet
Joined
Jun 5, 2022
Messages
15
Thank you. The plastic piece holding the rubber diaphram was cracked. That allowed water to escape through the hole on the thermostat housing, and subsequently got the bank of cylinders hot. A new one is on the way.
 

oildriver

Cadet
Joined
Jun 5, 2022
Messages
15
I bought this motor more or less sight unseen a couple of weeks ago. $500 with a beautiful rolling,really well balaced, narrow width square tubing stand. The tilt trim needed an o-ring on the manual release which with a good flush of the system now works like new. I also flushed the lower unit oil which had no trace of water to begin with.This motor shifts sweetly. I.When I started it, the water flow wasn't strong and it got too hot to keep my hand on the cylinder banks. I removed the cylinder head covers to find salt and silt packed into the thermostats, though the water passages had no blockage. After installing new thermostats and a new water pump, I ran it again. The port bank ran cool, but the starboard was still running too warm. Before I got the new valve for the thermostat housing, I ran the engine without the housings for a good amount of time. A good deal more gook flushed out of the system. I observed better water flow on the port side, but the starboard seems adequate. With the housings in place, but no thermostats, both sides stayed approximately even temperature. I have the new thermostat kit, but I had a complete hip replacement 3 days ago, so switching 400+ lb motors on the boat, in the water,with my dock mounted hoist, seems to be frowned on by my surgeon, wife, etc.My boss on the other hand wants me to come back and deliver heating oil and diesel to boats. I turned 68 3 weeks ago, so I would like to get a couple of fluke, but I guess it'll have to wait.If the engine turns out to be a honey, i will use it until I fix my 94 225 Evinrude. Then I will put the 235 on my old 21' Proline cuddy, and sell it to some lucky person for $2500 or so.
 

jimmbo

Supreme Mariner
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May 24, 2004
Messages
13,021
Boss spelled backward, is Double S-O-B

68? Retire already.
 

racerone

Supreme Mariner
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Dec 28, 2013
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36,462
Compression test should be done on the 235 HP.-----They are famous for broken piston rings.
 

oildriver

Cadet
Joined
Jun 5, 2022
Messages
15
I posted the compression test earlier. It was exactly 75lbs all 6 cylinders. I will run it on the boat in a week or two( my hip needs a little healing). Then I will do another compression test.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,462
75 is way low.----But perhaps find a " known to be good " gauge.------At a true 75 reading here on one of my 82 models the engine would be torn down for work !
 

oildriver

Cadet
Joined
Jun 5, 2022
Messages
15
I read a post that the original factory was 85-95. I did the work on that premise. I guess you are saying this is not so. I remember a friend(omc mechanic ) who had a late 70s -early 80s 85hp Evinrude who had an evinrude that ran well at 50lbs. Maybe I will get lucky. I am not looking forward to doing rings or more. The gauge is known to be good.
 

oildriver

Cadet
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Jun 5, 2022
Messages
15
One more thing. You say you have 2 235s on your boat. What is your compression, if you don't mind me asking?
 

racerone

Supreme Mariner
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Dec 28, 2013
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36,462
Some want to doubt and argue.-----You want about 120 PSI on your 235.------My guess is you need a better gauge !!
 

oildriver

Cadet
Joined
Jun 5, 2022
Messages
15
You may be right about the gauge, though it is reasonably new and has provided what I thought reliable results on other motors. I will retest (dry and wet)with this and another one. If I still get those low numbers, I will pull the heads to inspect it.
 
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