Thanks in advance for your help. I have spent all summer trying to solve the problem below. It has put a real damper on my family’s love for boating. My wife and I have 4 kids and we always fill the boat up with their friends + kids at church ( I am a pastor and have found great joy in making this boat a part of our youth program). Well over 100+ kids have had fun in our boat and I am very discouraged.The Boat:1999 Chaparral Sunesta 232Volvo Penta 5.0 liter GiFresh water cooled.170 hours ONLY! On engine.Fresh water 80% of the time salt water 20% of the timeMeticulously maintained. I flush the engine (using salt away) for 30 minutes whenever I get out of the water and scrub the boat down for 2-4 hours.The engine purrs like it is new.Problem: High speed overheating: Cruises at 7 knots all day long but heats up aggressively after 20 seconds on load. When I back off on the throttle everything returns to normal.What I have done: I have changed the: thermostat, and impeller. I have cleaned out the thermostat housing as much as I could. I have taken off both exhaust manifolds and risers and cleaned them (High speed pressure wash) and soak in phosphoric acid (naval jelly) dilution of water in a 5 gallon bucket for 8 hours. I have swapped manifolds and elbows on both sides because….. here is the problem:The left side of the engine is always much hotter than the right. You can rest your hand on the right manifold and elbow with no problem but the left side is hot to the touch.Today I measured the water that comes out of both sides of the thermostat housing and it was identical (8 cups in 10 seconds). I don’t know what else to do and I cannot afford to take the boat to a mechanic because we can’t afford it (the economy wasn’t what it was when I bought the boat). I am comfortable working on the engine as I have a mentor that will show me what to do. He is pretty stumped as well.Thank You GentlemenGod Bless you,Ariel BabikianPasadena California
Make (of engine): Volvo Penta
Model (of engine): 5.0 Gi
Horsepower: 250 I think
See details I typed in prior field.
There 3 things that could cause this problem. 1>Ths hose from the drive that supplies the water to the engine is leaking, causing air to be drawn into the water supply.Could be the hose connected to the drive or, The fitting on the drive the hose connects to, or the water pump hose barb is loose. Some of the earlier pumps had a fault with the pressed on plastic hose barbs that would turn and leak. 2> Ehxaust gas is getting into the water system through the head gasket..To check this , Remove the thermostat housing and run the engine at idle, water will come out. Look for bubbles then try at higher rpm. There should only be lots of water and no bubbles. 3> This is only if you have flapper valves in the exhaust 'Y' pipe. One piece has broken off and loged into the bottom of the pipe.
Thank you Sir. I will check all my hose fittings and hoses again for possible leaks (which I am pretty sure are tight because I have checked them many times). maybe a pinhole somewhere I cant see or between the intake on the outdrive and the impeller?
Also: My friend who can pull an engine apart to the bone (but is not an expert like you) was saying your #2 is probably the case but I am scared of making the deal bigger. I probably wont think so once I get the head gasket off. Finally, I am not sure what a 'Y' Pipe is but I'll find out. It is probably appropriate to say that the more I think about all this stuff going on I can trace it back to teh end of the last season that I changed the bellows and ?? one other "pipe". If I pay you now which I am totally willing to do does that mean I cant ask you any more questions? Do you see me through the problem or do I pay for questions along the way? This is my first experience with Justanswer and so far I am very impressed. Thanks :)
When you get an answer that you deem acceptable then, click accept. We generally try to see you through the problem , first. But you can accept as many times as you like. ...Changing the universal and exhaust bellows could not create the symptoms you have.The water hose, possibly.
30 years professional marine mechanic=skilled in all phases of the marine service industry.