GP1200 fuel starvation/lean condition?

[ADDict]

Fuel pressure is 2 psi idle and about 6 when I brap it open using a calibrated fuel pressure gauge right before the restriction.
Man I never considered the octane at 150psi.. I'm running ethanol free 93 40:1 with klotz. Maybe I should have a go with 50/50 110/93.
Thinking I need to find a stock head, or get bigger domes.

 

[WFO Speedracer]

So you are thinking DETO, with that much pump load it is defiantly a possibility

Fuel pressure is 2 psi idle and about 6 when I brap it open using a calibrated fuel pressure gauge right before the restriction.
Man I never considered the octane at 150psi.. I'm running ethanol free 93 40:1 with klotz. Maybe I should have a go with 50/50 110/93.
Thinking I need to find a stock head, or get bigger domes.

After thinking about it for a minute my best guess is that the cylinder temps got way to high at WO throttle and the engine was not running out of fuel but actually seizing and releasing, the conditions on which an engine will shut down due to lack of fuel or excess heat are very similar and it would be easy to mistake one for another. The damage to the pistons tends to support this hypothesis..

 

[spinyard]

do yo u still have the stock fuel selector valve in place? what about the pickups in the tank? if so try swapping to reserve when you see the issue

 

[WFO Speedracer]

Do you by chance still have the damaged piston you took out of the ski so we could look at it ?

 

[ADDict]

do yo u still have the stock fuel selector valve in place? what about the pickups in the tank? if so try swapping to reserve when you see the issue

No, it has been bypassed and pickup has been pressure tested.

 

[ADDict]

Do you by chance still have the damaged piston you took out of the ski so we could look at it ?

I think so.. I at least have pics. I'm out of town right now but I'll be home this evening and will post photos of the past damage as well as pull the head for current photos.

 

[ADDict]

Just looked into lower compression domes and looks like that's not an option. I am running 42cc domes currently and that's the biggest dome they sell (on their website anyway). Guess I'm looking for a a stock head/hardware now.

 

[WFO Speedracer]

If you want to work out a tradeout on that head for a stocker and hardware I am sure we could work something out, I am building a Waveblaster ll and I could use an aftermarket head. I will throw in a new head gasket as well.

 

[ADDict]

Well, I feel dumb as hell. It was compression.
I installed the stock head (likely machined by sbt) and now I'm at 120psi across all three cylinders and my boat runs like a top.
I can't thank you guys enough for the help.

 

[WFO Speedracer]

The triples are a lot more finicky about compression than the twin cylinders, truefuloly if it was installed in a Waveblaster you might have never had an issue, I think the sheer mass of that boat complicated the problem, triples suffer from something called torsioning which quite simply put is crankshaft twisting over the length of the shaft, the more load it is put under the more torsioning occurs .

This is why Yamaha went with staggered compression and staggered timing on 1200's versus the setup they ran on the 1100's, they actually lowered the compression on the rear cylinder and the timing is retarded by a few degress, that way when the crankshaft twists under load it doesn't matter.

 

[WFO Speedracer]

I do want to add that I am glad that fixed it and that you updated the thread saying what the problem was.