Won't start. Again...

[mejim707]

Per a lot of posts on my last carb rebuild I replaced all the seals, brand new needles and seats and put it back on the water on Saturday. The boat ran like a monster. Man that thing is fun. I was getting up to 7k RPM with no hesitation. I know the carbs are running good but a few things happened.

I got real far away and parked it at a dock. About an hour and a half later I returned and it would not start. I pulled the plugs and sure enough they were wet. I left them out for a good 45 minutes and popped them back in but still would not start and was fouling the plugs. Needless to say I had to get towed a significant distance back to my launch. Awesome guys hooked me up but it's kinda embarrassing when you have guests and you get stranded like that. Anyway, it looks like another rebuild is in order and I'll be yet again buying a new set of needles and seats. Unreal.

Any other ideas why these carbs keep leaking? The pop off pressure tests were successful and like I said these were brand new needles and seats.

Thanks

 

[mejim707]

These are what I purchased and they leak
https://www.amazon.com/gp/product/B000N5UV5Q

 

[mikidymac]

Those are genuine Mikuni parts so that should not be an issue. I would check the carbs for leakdown to see if they are actually leaking.

You don't have to remove the carbs. Just do one carb at a time, plug the return fitting and on the inlet make sure it holds 10 psi.

 

[mejim707]

I actually did that per your instruction after the rebuild was complete @mikidymac They held 10PSI. The mag held for about 24 hours and the PTO held over night but far longer than the 10 minute window.

I'd hate to have to remove these again but this is the only thing preventing the boat from being 100% complete and reliable.

Thanks for the reply!

 

[mikidymac]

I would double check for holding pressure but don't pull the carbs.
Something is causing it to flood when sitting and that is the easiest place to start with.

 

[mejim707]

Will do. I'll try to get that done tonight. Thanks for the tip!

 

[Jayson24k]

Have you tried pushing the start button (you should see light), then put the key in, and push the start button again.?

 

[gazzaskirepair]

What’s the compression on each cylinder ‍
Is it oil on plugs or more fuel than oil ?
The center crankshaft seals fail causing a heavy oil mixture
Poor a little fuel in each cylinder to if it will fire up
Clean plugs up first then see how long it runs for and then pull plugs again to see if dry or oily

 

[mejim707]

@gazzaskirepair Thanks for the replies fellas! Yes, I think I have good spark. It will start up and run like a monster for as long as I have it running. It runs cool where the exhaust is warm even after extended WOT.

The compression last I tested was 145 each calendar from what I recall. Maybe 140 but they were both about the same.

I'm pretty sure it's primarily gas on the plugs. They are wet and smell like fuel. I'll try the suggestion of running it for a while then immediately pulling the plugs to see if dry or wet. That's a good idea since it'll show if it's running rich the whole time or not burins the fuel fully.

@POPPS I did open the electric box and reseated all the cables with dielectric grease. I'm pretty sure electrically it's good.

It's just after running for a while, then shutting it off that I saw how flooded it got. I need to pull the plugs right after a run though to see if it's flooded after running for a while instead of sitting.

I also have to try the other suggestions as well. It's been a busy week but I'm getting back at it.

 

[gazzaskirepair]

I suspect center crank oil seals are bad causing to much oil/ fuel fixture

 

[mejim707]

@gazzaskirepair How would I go about confirming if this is the case? Would this require the entire engine to be rebuilt? I'll be conducting a pressure test on the carbs tonight per @mikidymac suggestion.

If I was getting too much fuel / oil during run, wouldn't this affect the performance? Like I said, the boat has excellent power for an extended period of time and does not get 'loaded up' as others have reported. If the fuel / oil was too much during run, wouldn't the performance degrade due to getting loaded up with unburned fuel?

I can run the boat for hours at all throttle levels with seemingly no issues. And if I punch it I'm at 7kish RPMs and that thing just jumps out of the water and goes like a cheetah. It's only after stopping for a while that I see this issue.

Thanks for the reply.

 

[mejim707]

@Jayson24k When you say push the button, then put the key on and push it again, what should this do differently than just trying to start it?

Thanks for the reply

 

[noviceskier]

Has the stator and regulator been ruled out? Sure sounds like a leaky carb, or even poor compression?

140psi isn't poor, rectifier wouldn't be the symptoms he is giving, wet plugs means it is flooding, that is the issue from my perspective. Check the pressure relief, clogged? If system builds too much pressure from the fumes when sitting out in sun, building pressure till fuel leaks from seats I could see that as the issue, iirc it should pop at 6psi

 

[POPPS]

For that much fuel, and you have new parts, I would lean toward an error in assembly of the carb. A leaking O ring at the seat could cause your flooding, it's a new carb kit, so the needle would not leak. If the spring was not seated properly under the arm it would close the seat and cause a lean condition. Perhaps the spring arm is upside down. It's even possible that the very small orifice of the return line, is plugged, causing excessive fuel pressure at the needle.

 

[mejim707]

@POPPS I hear you. But I will say I was extremely careful with the assembly and went over everything thoroughly. I did the pop off tests and after minor adjustments both carbs were within 1 PSI of each other. All seal were also replaced with genuine OEM parts as well. I also did the pressure test and they both held 10PSI with no loss for hours. If I got something wrong them I'm not fit to touch anything mechanically lol

@noviceskier That's a good point. I'm going to bring it down to the lake and run it for 20 minutes or so. Then I'm going to dock it at the launch and wait 20 minutes as a test. I'll first do all the preliminary tests before I bring it but when I get it there I'll do as you suggest and loosen the gas cap while it sits.

This is literally the only thing wrong with the boat preventing it from being 100% perfect.

 

[jts32]

The boats don't have a pressure valve like the skis. They have a thru-hull vent designed to keep water out, and shouldn't allow the tank to build pressure. Possible it's plugged up

 

[Jayson24k]

@Jayson24k When you say push the button, then put the key on and push it again, what should this do differently than just trying to start it?

Thanks for the reply

So when I first got my boat, the previous owner thought that there was an issue with the battery. She would put the key in and try to push the start button and you would hear a clicking sound. We charged the battery, took it to the lake put the key in and the same thing. After doing this a few times I was getting frustrated but wanted to try something different. So I jump back into the boat, push the start button till i see light on the gauge, put the key in and push the start button again and voila. It starts everytime.

 

[POPPS]

Have you load tested the battery, I have had batteries that would start the ski, let me get out about 100 yards, and then foul a plug. The battery was strong enough to start the motor, get me going, and foul, the spark turned out to be a dull yellow, but not the preferred bright white blue. I put in a new battery, and that solved my problems. I went thru everything, carbs, coil, wires, connections, and in the end, it was as simple as a battery with a bad cell.

 

[brownie545]

Having the same issue with my boat. Gas flooding the engine when not running. Ive had to turn it over with the plugs out to get enough gas out to not foul the plugs instantly. Im assuming as others have stated that its a carb issue. I have been shutting the fuel selector off when I know im stopping for more than a couple minutes and running some of the fuel down in the lines. Starts perfectly every time after that.

 

[mikidymac]

Leaking needle and seats.

 

[POPPS]

Could the return orifice be plugged?

 

[H€PHÆ$TU$]

The boats don't have a pressure valve like the skis. They have a thru-hull vent designed to keep water out, and shouldn't allow the tank to build pressure. Possible it's plugged upView attachment 44392

My tank releases pressure any time I open the cap.

So you're saying I should be able to flow air both ways freely through this?

I'm having an issue with one engine where it will not rev past 6500. If I try to get it past that it sputters and dies and is then hard to start for a very long time. This is a new sbt engine with about 8 hours on it. 150+ psi compression and plugs look perfect. The other engine, which is also new but I built myself, runs fine all the way up to 7000.

Could this be a symptom of a that vent being clogged?

Also the previous owner does not have the sending unit vented. Instead he has the vent port hooked up to one of the carb return lines. But I also know this is how some skis are plumbed so I don't know if it would cause issues or not.