F150 problems x2

[HydroliftErik]

Hi,

i have a customer who bought a new boat with a new Yamaha F150

the first engine broke after 9,8 hours, and the reason has not been found out yet.
it has bad compression on all cylinders, and the third has zero compression.
Yamaha asked me to send them the engine for analysis, however, i havenīt got any answers yet.

the customer received a new engine on warranty(complete new engine, not just pwr-head)
and now, after just 5-6 hours with a new engine, the engine is difficult to start, and has bad performance.

checked the compression and it was pretty bad.
i asked the customer where he filled gas, and he does it at the same gas station as many of my customers, and myself, and no one has ever had any problems.

YDIS does not give me any useful information at all, and Yamaha neither..

so im in some kind of a situation here, i have 2 brand new F150 with bad compression and i canīt find any clues of what might have gone wrong?
please help me!

[boscoe99]

You would think that Yam would not build two blocks, each having multiple defective cylinders from the factory.

Something is causing the cylinder damage. My experience with the Yam F150 is that it is prone to detonation damage due to bad fuel. This is a relatively high compression motor that does not have a knock sensor.

Why not, beats the hell out of me. Yam finally introduced a knock sensor in the F115 but not in the F150.

Look at cylinders two and three. They are usually the ones that go first or suffer the most damage. Pull the head and what do you see? Parts of the edges of the pistons broken or maybe a hole in the top of a piston?

If the new motor was installed and run on the same old gasoline this might be the cause of it. Gasoline in translucent tanks will get old quickly and lose its octane rating. Motor oil or diesel fuel will contaminate gasoline and cause its octane rating to be lower than specs.

If I owned an F150 I would use no less than 89 octane. Maybe 91 just to be on the safe side. Also, make sure that the motor can turn at or near 6000 RPM when it is at wide open throttle with the boat loaded.

What country are you in? The use of the comma in 9,8 leads me to believe you are not in the United States.

[HydroliftErik]

Im from Sweden,
we only have 95 or 98 octane, and the customer have used 95 octane
we have sold around 5-7 F150 in this area, and everyone is filling gas at the same place.

[boscoe99]

What is the common link to two completely different motors, both with similar failures?

The operator, possibly the propeller, and the fuel supply.

Is the motor propped so as to get at or near 6000RPM when the boat is loaded?

New boat or repower? Has the fuel supply been tested. With 9,8 hours on the first one and 5 - 6 on the second one, I would thoroughly test the fuel system and supply. Yamaha is not going to continue to provide replacement motors that are damaged due to some external influence. Some engine makers seeing detonation damage (if that is the case) won't do anything to help the customer. Detonation damage is not a warrantable defect. Congratulations for Yamaha helping out.

The F150 does not consume much fuel to begin with. Given the size of some fuel tanks here in the states, and if the boat in question is the same, it is possible that both the first motor and the second motor were both drinking the same fuel. Maybe someone spiked the fuel by adding a little diesel. Or, maybe some contamination happened by mistake. Maybe the fuel was bad to begin with. Who knows why? You add clean fresh fuel to bad fuel and you still have bad fuel. What does the fuel smell and feel like? Diesel or oil will make it seem slippery.

If the propeller is the correct one for the application, if the customer has some experience in operating outboard motors, then I would focus on the fuel supply and system. Or, throw a third brand new motor on the boat and see what happens.

[TownsendsFJR1300]

Drain a little bit of fuel from the reservoir that hold the fuel pump, on the starboard side (with the clear plastic hose attached to it) into a super clean container(I use a steel tuna fish can), you should be able to see and smell the fuel for any contaminates, stale gas, etc.

That or prime out some fuel direct from the tank and examine whats in the tank. There's not much else to fry two engines on the same boat as posted above...

Besides poor performance, I wonder if he sucked some water into the engine from the tank and broke the internals causing the major damage...(yes its new, but someone may have left the cap open, not rigged correctly, etc)

Over here, ethonol fuel breaks down in as little as a month and causes issues too.