1997 Evinrude Ocean Pro 150 Overheating at WOT - E150SLEUC

Hi All. I'm having a hard time figuring out an overheating issue mostly just at WOT (or close to) with my Ocean Pro. This is a new to me engine that came without thermostats. Has been a salt water engine from someone I actually knew (not well but trust him). I replaced water pump with 5001595 Water Pump Kit. Compared to old one that came off to make sure, and looks the same. I'm using my MPH gauge as a water PSI gauge for time being, based on me testing psi with air compressor, looks like I'm getting around 20 PSI at WOT. the temp shows the engine going up to around 180 degrees at cruising speed, but my infrared temp gun shows top of cylinder head closer to 150-160. The HOT alarm and SLOW function does kick off after running a bit at WOT, but does not kick off under 4,500 RPM. I have the blue / tan wire which I believe engages hot alarm at 207 degrees.

Observations and actions so far:

I'm going to take a few degrees pitch off prop but current WOT is around 5,200. I replaced carb bowls as they were warped and tried cleaning up just as preventative maintenance. Hit all orfices with compressed air when I had them off.

I disconnected VRO pump per lots of advice I've seen on here. Basically just plugged up inlet for oil hose and disconnected the 3 wire pin connection. I've heard people talk about vacuum warning, but it's clearly the HOT light / alarm. I pre-mix 50:1 fuel/oil.

I took off heads, blew air through passage ways (definitely was some calcium buildup), replaced O-rings on cylinders, replaced thermostat seat/seals, and torqued heads back on around 17 ft/lbs per manual.

I have run a few times alone on the boat at WOT without alarm going off, but with 2 friends aboard yesterday, problem persisted (going in right direction but need a legit fix).

I will note that when thermostats are out, boat runs cool at all RPM ranges. Obviously this is not a good long term solution, but seems fine without restriction of thermostats. There has not been any clear blockage in the new thermostats that I have installed.

Lastly - I used CLR + water to pump through water system via an inline pump for 3-4 hours to try and help clear and clean up cooling system. Also soaked heads for about an hour when they were off.



Wondering:

Is 20 PSI +- enough water pressure? If not, what do i need?

are thermostats not coming off seats at high RPMS to allow enough water into heads? I even went down to 143 degree thermostats (engine calls for 165 degree) to see if it would help - not really.

Could engine be running lean at WOT? You cannot adjust this from my understanding besides just getting new high speed jets.

Timing - have been meaning to check but didn't know if this could lead to hot running engine.



Thanks for any thoughts and help. Close to taking to mechanic but hard to troubleshoot when you're not on water. Idles fine and runs at right temps at lower RPMS.

Factory kit or an AMAZON item ?

Amazon... via company UANOFCN? Still pushing 20 PSI up into engine, not enough?

I have also read that some of these year models came with high speed jets that were smaller than what they sell today. When I put new bowls on, I realized (after the fact) that they did not have the high speed jets in them. It obviously did not run well bc it was running rich but it did run way cooler. This gets back to my running lean question, will pull a high speed jet tonight to see what orifice size I currently have. On Marinengine, looks like they discontinued #59 and only sell #70 and #69.

Well----61D / 62D / 63D are available.----Hurry consult your local boat shop for details.

Parts catalog calls for 69 or 70. Took out top two high speed jets and saw they are 69d so think I’ll rule that out. I did clean them again but they looked pretty clean as is.

Just a quick update after another test run. Ended up just taking out the spring on the right, starboard thermostat. concluded first of all that it is just the right side overheating. Definitely ran a little cooler around 130° at idle but capped out around 160° at wide open throttle. going to call the local Evinrude dealer today to see if there was possibly a wrong spring that was used. Just odd that the same springs are on the port and starboard side but only the starboard side is overheating.

still trying to confirm if 20 psi is high enough pressure for this engine?

I wanted to update and provide my findings largely because it was a very specific problem. After inspecting with lower unit off, using telescoping camera and flashlights etc., I came to the conclusion that there seemed to be a leak in the exhaust housing. I had to pull off powerhead, which I then found some corrosion in the water way in between the exhaust ports (of the exhaust housing). I can try to upload pictures if anyone would like.

I installed new exhaust housing (used but very clean from freshwater engine), put new gasket between housing and power head. Made sure all looked well in the pump and housing (for like the 3rd time haha), tested pump with power drill to confirm it was pumping. This appears to be what the issue was.

Took out for test last night and kept within temp range 10 degrees +-. Honestly I only got it up to WOT for a short time as it was rough and busy but am very confident that was the fix. There was very little information on this potential fix. This has been primarily a saltwater motor which I'm sure led to that corrosion and failure of the exhaust housing/water inlet channel.

Darndest thing but feels good to have a fix!!!