Why does the 350 chevy in my I.O. boat still run hot after extensive work?

Question

I have run this 26 ft. raw water cooled boat for years with no thermestate getting an engine temp. of 150 when running at a full speed of 25 mph at 4200rpm. Last summer the boat ran slow for the last 4 times out because of what turned out to be a fouled carborator. I was glad to find full power restored this spring with carborator now professionally checked out but reinstalled by me. (Idle air/fuel settings done by the book after installation) The problem is the engine now runs hot (160 at idle up to 190 at 2000 rpm) That gives me 8 mph. A higher rpm will cook the engine. I have checked the temp. sensor and gague for accurace, changed outdrive pump impeller, cleaned manafolds and risors, installed a new engine circulating pump, varified proper timing and timing advance, checked compression and inspected spark plugs which looked too clean so I rechecked carborator settings incase they were too lean and checked for leaks in carborator gasket and intake manefold.

Answer 1

Is water coming out the "pee hole" as it's called on the outdrive? Sounds like you are not getting circulation

Answer 2

Check and make sure you haven't got a restriction in a water inlet line.Also are there any hoses that could be collapsing and restricting water flow?

Answer 3

Keep looking as there is a restriction in the cooling sys> And did you check the discharge holes in the risers they corrode and close up restricting the water flow>You should have a thermostat 140 deg to slow the water down> As 150 is hot for a open cooling system>Pull the exhaust hoses off and look inside between the SS sleeve & housing> Have had to drill the holes out as they plug up>