engine question

[el jefe]

I am not sure if I can accurately describe the question I have but I will give it a shot by comparing my two 225 four stroke yamahas. When the are both on, one is quite, pees just fine and the water around the shaft is still. The other pees fine, but bubbles a lot of water coming up from the prop. The water bubbles up the shaft and where the other one still, the second is well, bubbly. When I put the two engines in gear at the dock the still engine spins a clean cavitation tube off the prop. The bubbly engine seems to be pushing out a lot of water from the prop and is much rougher. When I went to wash out the engines I really noticed a difference. The still engine had water coming out the pee hole, which meant to me that fresh water was running through the engine. The second engine had no fresh water coming out the pee hole but plenty coming out from the hub/prop location.
I haven't had any problems with either engine so I am wondering is this normal or what. I just cant get my mind around the fact that the two engines are so different in appearance while pushing out water. Thanks.

 

[Moxsea]

You need to check two things: 1) thermostat & 2) pressure control valve. Had similar problem turned out to be t-stat seized open(for me).

 

[Tashmoo]

Did you have the lower unit off of the "bubbly" engine before this started?

If yes, you may have lost a baffle block out of the lower unit that is not shown in the manual, at least mine was not. I hit a rock with my last boat and had to send the lower unit out to be fixed which included welding a new skeg on. When they did so a black rubber block fell out of the lower unit that is some sort of exhaust baffle. The result was as you are describing plus about 2-3 mph more speed and a lot of noise coming from the transom area. The only way we found my issue was to sit two identical lower units side by side and there it was. Replaced the black rubber block and perfect.

Hope yours is that simple.

 

[el jefe]

Update report. After getting the boat out of the water, dropping the lower unit, it was determined that a significnat corrosion problem existed. According to mechanic, the internal metal was severly degraded. Then checked other engine and signs of corrosion were found. Issue was presented to Yamaha even though engines were three months out of extended warranty. Yamaha responded by providing parts and labor for complete replacement on both engines. Talk about customer good will. So the corrosion problem is real on the 2004/05 engines, should be checked when doing annual service. My signs of problem were water shooting out of exhaust port and as desecibed previously heavy bubbling from prop. I wish I had pictures taken to post.

 

[BobP]

Sounds like the issue covered to the nines at THT on the F225s.
The THT threads show the photos. The metal was defective material or improperly coated for the application and disintegrated, as the cause.

I believe it's the exhaust manifolds in trouble, may be wrong on the part name, if the same as you have.

That part should last indefinitely, period!

At least you didn't break down at sea, motors have been wrecked by the defect.