225 Yamaha OX66 bogging at high rpm - The Hull Truth

fishingluv · 03-03-2010, 04:52 AM

Twin 225. At high RPM, I lose Starboard power quickly, then the engine shuts off. Will not restart.

Actions so far:
New 10 micron fuel filters.
New filter inside the engine (the small one on the port side of the engine)
VST filter replaced.
O2 sensor swapped out with the Port engine.

Fuel pumps?

Thanks in advance

lostsinker · 03-03-2010, 06:21 AM

Quote:

Originally Posted by fishingluv

Twin 225. At high RPM, I lose Starboard power quickly, then the engine shuts off. Will not restart.

Actions so far:
New 10 micron fuel filters.
New filter inside the engine (the small one on the port side of the engine)
VST filter replaced.
O2 sensor swapped out with the Port engine.

Fuel pumps?

Thanks in advance

After a while, does it start?
My initial guess would be fuel starvation due to any number of causes, blocked vent ( primer bulb will collapse, bad primer bulb, blocked line ( if before bulb, bulb will collapse, if after, bulb will stay inflated)
If you have two fuel tanks and individual fuel feeds, you could swap the fuel lines at the motors and see if the problem moves to the other engine.

Clogged or bad VST pumps/filters typically cause rpms to drop or cause the motor to not go above a certain RPM but don't usually cause the motor to stall.
One other test is to remove the cowling after the motor stalls and see if the fuel filter bowl is dry.

The issuse is not likely to be O2 sensor related. Low pressure fuel pumps could be an issue, but ususlly after stalling and priming the bulb, the motor will restart.

grin · 03-03-2010, 06:45 AM

Almost certainly the low pressure fuel pumps. 3 on each motor. Easy to replace and about $50 each.

wetneck · 03-03-2010, 07:42 AM

unbolt them, pump ball, if gas comes out of vac port, replace.

with a bad lp pump you will see a gas sheen on water,driveway

I would first check ball when it shuts off to see if it flattens.

you may have a clogged pickup tube screen

airleak in line

nickmo · 03-03-2010, 07:50 AM

If there's a way you can get a fuel rail pressure gauge on that schrader valve on the vst and run the boat. You can then see what the pressure is when the motor acts up. You should have about 35 psi when the motor is running. If the pressure drops, it's a fuel delivery problem for sure. I would change out those 3 low pressure pumps as grin suggests. I consider them a maintenance item. Change them every 2-3 years.

fishingluv · 03-03-2010, 07:59 AM

The engine starts right up when it is cold.

The ball is never flat, however I do feel that I can squeeze a bunch of fuel before it gets hard.

The boat will not restart for over an hour after this happens.

wetneck · 03-03-2010, 08:10 AM

which might suggest a bad diaphram, flooding cyls

nickmo · 03-03-2010, 08:19 AM

As wetneck says that points to a bad or multiple bad diaphrams. When you pump the ball you're dumping (raw) fuel in the engine. You're flooding the motor which is why it won't start. When it sits a while, fuel evaporates then it starts. Don't run it too fast in this condition cause the motor is not getting enough oil.

PRO-BLU · 03-03-2010, 10:57 AM

Fuel pumps and spark plugs! That ethanol eats those fuel pumps like it is its job.

fishingluv · 03-03-2010, 12:47 PM

fuel pumps are my next action. will do it this weekend. thanks everyone for the advice and direction. I'll post my results.

fishingluv · 03-16-2010, 08:48 AM

Thanks everyone. Replaced the fuel pumps. the middle one was blown, but changed all three. ran it full throttle the other day. great to hear them hum.
THT ROCKS!

nickmo · 03-16-2010, 08:54 AM

Quote:

Originally Posted by fishingluv

Thanks everyone. Replaced the fuel pumps. the middle one was blown, but changed all three. ran it full throttle the other day. great to hear them hum.
THT ROCKS!

Don't you love happy endings!!!