Yamaha SX 150 TXRY............Stalling

[Bob Gilvary]

The problem started with the boat owner not being able to get over 3600 rpm's before the engine would stall out.

I changed spark plugs, and a new fuel water separator, then water tested. It ran better, got to the 4500 rpm range, then stalled out.

I checked out the high pressure fuel pump filter. It was clean. I took off the fuel rail to be sure some water had not accumulated in the bottom, it was also clean.

My fuel pressure gauge showed a constant 35# at all rpm ranges until it stalls, and once it stalls it takes several seconds for it to start again. It's like it has to wait to pressurize the system again.

I checked the fuel pick up at the tank, no screen on it. No anti siphon valve, new gas line from the tank to the fuel filter, new primer bulb. I've even been pumping the primer bulb when it stalled.

I tried to look at all the basic BS and be sure it was in good order.

Today's water test started out fine, until it got up to 4500 rpm's then it stalled and went down hill from there. Stalled at 3600, then stalled at 2000, then finally kept stalling when at idle.

Anybody have a suggestion, or answer as to what is causing this stalling?

 

[Bob Gilvary]

Re: Yamaha SX 150 TXRY............Stalling

I've read several other posts on stalling, but nothing with this particular engine.
I'm going to recheck the fuel rail and be sure of proper o-ring placement on the injectors, then the filter at the fuel regulator, and the fuel delivery assembly after the engine filter.

I'll be back!

 

[Bob Gilvary]

Re: Yamaha SX 150 TXRY............Stalling

I thought better of checking the fuel rail. If those o-rings were not in correctly, I'd have at least a bad idle.

No other sign of a clogged filter, so I didn't check the filter at the regulator either.

I did take the "fuel delivery assembly" apart and removed the spring and piston in it.
It ran great on the water after that.

The motor always did stall at wide open throttle, and still does. Another mechanic replaced all of the injectors, and didn't fix it.

It seems that there is/was a restriction that kept the vst from getting the required fuel to run at sustained wide open throttle.

I did find a smaller diameter fuel hose between the fuel/water separator and the primer bulb. I replaced that with the same size as what was going from the primer to the engine filter.

Not sure if that corrected this issue, but the owners happy that it doesn't stall at idle any longer, and he can run as he usually does, at 4400 rpm's.

 

[Bob Gilvary]

Re: Yamaha SX 150 TXRY............Stalling

Update from the boat owner;

"Bob, that's the best this boat's ever run. I topped it off with fresh fuel and took it down to Calabash and back. Runs great."

That's the kind of calls I like to get. Now, anyone out there that can give me a purpose for this fuel delivery assembly, and I'll stick a new one back in it.