Carb HP500 Oil Overheating?
 

Water Presure is at 20psi just like port eng, Water temp is 130 degrees just like Port eng but Oil temp stays at about 220-230 at cruise and got up to 280 at full throttle. I immediately came to idle and it went back down to 220. Port eng never gets above 180 degrees. Where should i start to look for this issue? Sticking Thermostat? Trash clogging water impeller pump? Any help would be appreciated. Also, I just had the oil changed and since it got up to 280, do you think the oil is now bad?

Thanks.

I would check the water flow out the back of your pipes and compare it to the other engine. See if the flow looks the same. Next, check water pump impeller. If you have missing blades, then you most likely have some rubber clogging up your flow. I had that happen and I had to back flush it with a water hose to get the rubber pieces out. If all looks good, replace thermostat or take it out. I don't run a thermostat. Make sure your oil pressure is good. By the way, my water temp does not get over 100, but my engines run about 230-240 degrees. 280 degrees too hot. I would change oil if you find the problem.

Verify it is actually hotter with a laser thermometer. Could be a bad sending unit.

would the water pressure gauge still show 20psi on both motors if a blade was broke off the impeller and clogged? Where/how easy is it to check for this and clogging? also, so i can just take the thermostat all the way out and it just stays as cold as possible? thx.

My first guess would be a lean condition. You might swap carbs side to side to see if the issue follows. Also validate timing at 3500rpm.

Your water pressure on both engines showing 20psi kind of throws me off. It does not hurt to check it. You have to take your waterpump off, open it and check it. I assume you have the external belt driven mercury water pump. At that point, you might as well replace the impeller. If any blades are missing, they are somewhere down stream. I was told there is an inline screen that suppose to catch rubber so they don't get clogged in the engine block, but I could not find one on my boat. I followed the hoses to the last point I could reach and find down stream, opened up the hose and blasted it with a waterhose and pieces of rubber came out where I had the water pump taken off. If you ran your boat on the trailer dry, you may have a damaged water pump impeller. Some people think it is OK to run their engine at 4000+rpm on the trailer with a water hose. Don't do that.

First thing is to verify the oil temps.
It could be that the oil is not circulating/flowing through the oil cooler adequately.

He says his water temp stays the same only oil goes up. So water flow ok. Oil filter may have collapsed. Or doesnt flow enough. What else was done? Doubt bad sender since it wouldn't work at all unless its loose.

Does that motor run an oil thermostat? Water goes to oil cooler first sO motor thermostat would make no difference if water temp stays at 130.

I would take out the thermostat and try it. They don't last forever.