1998 50HP SPL Poor performance at low engine speed

[atistang]

J50TSLEC Remote, electric start, primer on the key, 2cyl.
I couldn't get the engine to fire up this spring, I found the primer solenoid had gone bad. I replaced that and the fuel lines to and from the solenoid. Now I can get the engine to fire up without much hassle, but it will only idle about 5-10 seconds before it dies. I have the selector on the solenoid in the correct position.
If I give it some throttle it will usually stay running but on one cylinder until about 3500rpms or so and then the other cylinder will come alive. Needless to say under 3500 or so rpms it doesn't run great.
I rebuilt the carbs thinking maybe the idle circuit of that carb was gummed up, no change in performance. I then decided to do a link and sync and discovered that it was way off (long story on how that happened, but it is noticeably better now, before I couldn't hardly get it to run even with throttle). I've tried new spark plugs, no change.

I know it is running on one cylinder because I can pull that plug wire and there is no change, my hand will tell you that there is spark though lol. I'm going to test the spark gap today, but I have a feeling that isn't going to be my issue.

Also I tested the compression and got 148psi on both cylinders.

Its strange because the solenoid actually went bad last season but I was able to still get around by flipping the bypass lever and squeezing the bulb to get it started, but even flipping the lever back it didn't do well at low speed, before I did anything the spring it wouldn't even fire.

Anyone got any suggestions before I throw in the towel and pay the boat shop?

 

[racerone]

The high speed jet is found screwed into the very bottom of the float bowl.-----Did you have those out and are they confirmed clean?

 

[atistang]

The high speed jet is found screwed into the very bottom of the float bowl.-----Did you have those out and are they confirmed clean?

Yep. Took them all the way out and checked them visually. Also dissembled both carbs and ran them through the ultrasonic cleaner then blew everything out with air.

The only part I noticed that concerns me is there is some play in both throttle shafts, not sure how much play is normal. I didn't remove the butterflys and shafts as I typically don't do this when rebuilding carbs. Starting to wonder if that could be an issue, maybe it is sucking some air between the shaft and carb body?

 

[racerone]

There are 4 things needed for motor to run.------Spark ( 3/8" gap ) at the right time.----Compression in each cylinder.------Compression in each of the separate crankcases.-----Correct amount of fuel.------Checked fuel pump diaphragm ??----It should be super easy to figure this out.----But I am too far away to touch , feel and hear your motor!

 

[atistang]

There are 4 things needed for motor to run.------Spark ( 3/8" gap ) at the right time.----Compression in each cylinder.------Compression in each of the separate crankcases.-----Correct amount of fuel.------Checked fuel pump diaphragm ??----It should be super easy to figure this out.----But I am too far away to touch , feel and hear your motor!

So 3 years ago the VRO went bad, I converted it to the old school pulse pump on the block. I pulled that pump apart and it looks brand new still. Diaphragm looks real good shape, nothing in the screen. I'll see if I have a way to test the fuel pressure and see what I'm getting. I'm going to attempt to check the timing at idle today also, that's one part of the link and sync I left up to the base adjustments.

 

[atistang]

Tested the ignition coil primary and secondaries they test good. Spark jumps a 7/16th gap on both wires.
Checked the flywheel index, its good.
Checked timing while cranking and it is damn close to 1 ATDC.
Fuel pressure is ~5psi while revving the engine to about 3500rpm (pressure gauge isn't a low pressure gauge so it was hard to get an accurate number there.

Now I did get it to idle in neutral and in gear. I turned the top carb adjustment screw out to a total of 4 3/4 turns from closed and it will run there. It idles at about 1400rpm in neutral and 1200rpm in gear (engine submerged in a drum of water). So what I am leaning towards is an air leak somewhere on the carb. I have seen some people have had the plastic plate on top of the carb warp causing a similar symptom, my best guess is this is what I have going on or I have missed something during the carb rebuild.

 

[racerone]

Should be idling at about 700 RPM in gear.

 

[saltchuckmatt]

Put an unlit propane torch next to the carb shaft and see if it revs up.

 

[racerone]

Checked the flywheel key ?

 

[atistang]

Put an unlit propane torch next to the carb shaft and see if it revs up.

That's a good idea I'll try that

 

[atistang]

Checked the flywheel key ?

If that was bad wouldn't the indexing of the flywheel be off?

 

[racerone]

That would be correct.----See post #4----In my opinion it should not be hard to find where the issue is with this motor.---Sorry ---I can not be any further help on this one.

 

[atistang]

That would be correct.----See post #4----In my opinion it should not be hard to find where the issue is with this motor.---Sorry ---I can not be any further help on this one.

Don't apologize, you're not reading what I've already done, so no help anyways.

 

[atistang]

Replaced the top plates, no change in how the engine runs, but I did spray around the throttle shafts lightly with starting fluid and low and behold the right side to the top carb throttle shaft is leaking for sure. I was careful to make sure nothing was going in the airbox and 6 times in a row I sprayed a little on that side where the shaft goes in and the engine would noticeably change tune.

That will have to wait until I get back from vacation, but I believe the required seals are in the carb rebuild kit... I hope they are anyway because I don't see them on a parts breakdown.

 

[atistang]

I cannot find the throttle shaft and bushings for sale. The shafts have some very small groves worn in them, the bushings appear fine, but ideally at this point I'd like to replaces the shafts and bushings.

What I did was lube the bushings with silicone, and added an o ring between the carb housing and bushing. I have the engine idling in gear (submerged in a 55 gallon drum) at about 900RPM (Book says should be 850) with the timing right at 1 ATDC. The trouble carb mixture screw is about 4 turns out. It doesn't run the smoothest, but I can let it idle in gear for as long as I want and it keeps running at 900RPM. So at this point I'm calling it good enough for the season.

If anyone knows where I can get replacement throttle shafts and bushings please let me know.