Weird idle issue

[Evil]

Out of water, it will idle/run fine. Once the pump is submerged and water goes through the engine, it starts to stumble and then finally will shut off. If I feather it, it'll stay running and once I get going(passed no wake zone buoys) it runs excellent.

I've tried upping my pop off(had 10psi at first), messing with low screw, can't seem to fix it.

It was a project ski when I got it, I resealed the motor(and carb) and leak down test passed. Tested both internal and cooling, both good. I've checked my head orings tons of time and they are always seated correctly. I had the exhaust manifold and exhaust surface on the jugs decked flat. Had a small water leak from a warped manifold.

I've realigned the engine/drive line/pump and its lined up excellent.

The only way I've been able to temporarily fix the idle in the water is turning up the idles which then makes out of water idle way too high.

Specs of the motor if it helps:
165 even compression
Ada girdled head
61x engine, jugs bored to 84mm
B pipe
Sbn44

Any help would be appreciated, thanks

 

[Freakie]

Not sure how you could run 10 PSI pop-off and what it is now....sounds like carb is loading up in the water and overich situation is stalling the motor before it can clean-out.....not sure what pop-off N/S and jetting combo is for this spec, but post up your numbers and pretty sure someone will advise

 

[Evil]

If I remember right the pop off is 18 now. Never looked at the jet sizes, N/S is 2.0. When I bought it, in theory it ran. He took the ski apart to do some hull repair.

I'll open up the carb today and check jet sizes.

 

[Big Kahuna]

read this............ taken from this link
http://www.x-h2o.com/index.php?threads/carburetor-specs-database-superjet-and-blaster-1.19403/page-3 Taken from Matt_E


Read this first. (Click "This")

Popoff pressure controls how much vacuum in the intake tract it takes before the fuel supply needle "pops" open.
In short, it affects the fuel delivery curve on the bottom end of the RPM range.
A lower popoff pressure will provide fuel sooner. However, excessively low popoff values may result in fuel dribbling.
It is very much dependent on the setup you run.

 

[orangefinger]

I am recommending the easy approach

I would suggest to return all your jetting to where it should !! be and start by upping the idle , the ski will easily run with no load on land, once u are in the water u have load which means even in idle the engine is already working , prop has to move water , and idle will drop , and if not jetted correctly die....

being that said your idle if set correctly should be higher on land and then drop to where it should be under load..... that's normal

same as any car once u put it in gear ....

 

[Evil]

What do you mean return all jetting to where they should be?

Also, I would have to double check but I'm pretty sure when the water goes through the engine is when it starts to stumble and not when the pump is in the water. Meaning the first 10 seconds or so it does idle in water.

I was thinking it was a water leak of some sort but after having the manifold decks resurfaced I'm not sure.

 

[Evil]

Low jet is 120
High jet is 140
Spring is 95g
N/S is 2.0

Low needle is 1 3/8