Resolution of my 250

[Cocoliso VI]

Glad to hear you are getting a new powerhead Smoky, its good to hear Yamaha will stand behind their product.
I have twin F225 on my Sailfish and have backed down on fish with water coming over the transom with no problem. However on the back of the Yamaha owners manual they warn about keeping a motor tilted down when it is not running. They say wave action can introduve water up the exhaust and damage the motor. I hear peolple who troll say they use only one engine when trolling. Yamaha recommends to keep the other engine running while out of gear or to tilt it up out of the water if stopped.
Maybe Yamaha knows something they are yet willing to share with the boating community.

 

[jethro99]

Did you shift quickly into reverse while still going forward? The prop can drive the engine backwards and the exhaust becomes the intake. Water is literally drawn up the exhaust and then into the cylinder heads and cylinders.

This is not a warrantable defect if this is what happened. It is induced damage. If so, Yamaha is taking care of you on a goodwill basis. Please don't let it happen again, if this is what happened.

The owners manual clearly says to shift into and out of gear at idle speed only.

 

[JOSH S]

Did you shift quickly into reverse while still going forward? The prop can drive the engine backwards and the exhaust becomes the intake. Water is literally drawn up the exhaust and then into the cylinder heads and cylinders.

This is not a warrantable defect if this is what happened. It is induced damage. If so, Yamaha is taking care of you on a goodwill basis. Please don't let it happen again, if this is what happened.

The owners manual clearly says to shift into and out of gear at idle speed only.

Think about this for a second. If what you are saying is true. :roll: The prop turning the engine backwards would grenade the motor. Slamming the motor in reverse does not make the exhaust become the intake. It might shear off output shaft or strip some gears, but it will not reverse the engines rotation.

 

[Capt Bill]

I don't know if the exhaust ports are that different from a 2 stroke, but I know for a fact that water can backwash into the bottom 2 cyl, on an OX-66. I think it can also happen on a 4-stroke. Much more likely to happen if the engine tilted down, not running, and a bottom piston has stopped in just a certain position. A Yamaha certified master mechanic told me that it can also happen, under the right conditions, with the engine idling.

 

[BobP]

Glad to hear Yamaha, as usual, comes up to the plate to keep a customer happy.

What you really don't know and never will is because the extent of the investigation is limited and if longer would become very costly to get closer to knowing, then it may always be down to more than one possibility.
Yamaha wants to make sure dealers do work / install right, so another reason for teardowns.

If you ever had the occasion to shut motor off while going forwad or reverse, don't.

If going at speed on one motor lift other one out of water if other one is off. Watch following seas conditions if trolling on one motor, I mean tough following seas with white water waves.

A wave climbing over cowl can't be prevented from getting in, it is not submergible. If water gets by throttle boddies, end of story. I have water stains on powerhead from waves, so watch water conditions to the rear.

Make sure cowl is fully latched, if unlatched, kiss motor goodby if solid water waves (not wash water) come up motor side to top.

Make sure girlfriend or child doesn't use control for hand rail and throw motor in reverse while at speed forword.

Make sure front of motor via lines, cables, etc., is tight.

If any of the above occur and motor dies, don't mention any of it when taking in under warranty, at least, I would not.

 

[jethro99]

Did you shift quickly into reverse while still going forward? The prop can drive the engine backwards and the exhaust becomes the intake. Water is literally drawn up the exhaust and then into the cylinder heads and cylinders.

This is not a warrantable defect if this is what happened. It is induced damage. If so, Yamaha is taking care of you on a goodwill basis. Please don't let it happen again, if this is what happened.

The owners manual clearly says to shift into and out of gear at idle speed only.

Think about this for a second. If what you are saying is true. :roll: The prop turning the engine backwards would grenade the motor. Slamming the motor in reverse does not make the exhaust become the intake. It might shear off output shaft or strip some gears, but it will not reverse the engines rotation.

I stand by my answer. It would be nice if the original poster could ring in on exactly what happened and when.

 

[richie rich]

Remember, even at idle the motor is going around 700 rpms...the exhaust valve is only open for a split second and has cylinder pressure exiting going against any water coming forward...when you stop quick you have one good following wave and thats pretty much it........if any significant water came into the cylinder, you'd blow a head gasket because you can't compress water...so you'd know right away when it happened....that's what happens to cars when antifreeze leaks into the cylinder...and SMG said the engine ran fine all the time....even if just a little got in and not enough to blow while running or even hiccup, that little amount would eventually steam out from the engine heat or pass down into the crank area....was there any white in the motor oil at the service change????....and your oil pump would continue to lubricate the cylinder walls every time you run........to have all cylinders rusty??? Sounds more like moisture got in when it was stored somehow and the pistons were asleep....maybe not enough fogging oil? How were the engines tilted during storage??