problems with fuel pump maybe? 1996 Sea Doo challenger 787

[Scubadave16]

Hello again.

Some may remember my recent post about my very troublesome challenger. It is still overheating, but things went from bad to worse to terrible when it sank at the dock a couple weeks ago. It had burnt through the exhaust coupler after I had just replaced it. By the time the marina called me the engine was completely under water. We pumped it dry and eventually got it started, but it hasn't really run well since. It will start and run although choppy and loud. but when I give it gas in neutral, it backfires through the carbs and seems to "run out of gas" when I hit the throttle. It just runs fast for maybe 5-10 seconds then dies. I took off the carbs and went through what I could. they seemed OK. I hit it with sea foam and no help. A buddy on my dock said to replace the diaphragm in my carb pump. but it looked OK. is there another fuel pump other than the one on the carbeurator? fuel filters seem OK.

what else could have been messed up being under water?

I am really starting to wonder if it has met it's omega. Haven't really had the thing running in 2 years.

 

[Seadoodoc]

Wise man always told me to reach for the low-lying fruit on problem solving. Backfiring is a function of plugged exhaust or is the choke on all the time? Potentially could be getting water continuously into fuel system if it's sunk that hard. If it did sustain underwater situation your eventually going to kill the crank bearings.

 

[Seadoodoc]

I fought customers boat for a week only to find out that the choke plates were sticking closed. Take off those stupid plastic housings and leave them off. They're designed for jet skis and they're turned upside down. If you turn that boat of yours upside down that's the least of your problems

 

[Scubadave16]

Thanks for the reply sea doo doc. i had the plastic housing off. choke plates def not sticking. It doesn't backfire all the time, just once in a while. maybe every few seconds. of course on a "regular" engine I would think that the timing chain had jumped, but just doesn't appear that this could happen on this motor or am I mistaken? plugs both firing; i checked.

your comment about exhaust may be on one correct track though. it definitely is not plugged. BUT I was having all sorts of exhaust cooling issues; not so much of the engine, but of the exhaust. bought another WR valve, but haven't installed it yet because the engine won't run.

also the beeper was coming on once in a while while I was running the engine. if I goosed the throttle a bit it went away, but then the engine would quit. tell tale water always coming out. hose into head is cool, coming out is warm. exhaust stinger pipe VERY warm.

additional info. I keep having to change batteries. think something is draining them while engine off. no idea what.

 

[Scubadave16]

back to my boat issues. I can consistently start the boat, but first it sounds different and runs rough. if I give it full throttle (which is about half throttle while in neutral) it runs a bit better but with a few backfires. then just quits after 15-30 seconds. it then starts right up again and the same thing happens. nice tell tale water stream; some smoke in the exhaust when I start it, but not much when running. I have pulled some of the fuel lines and the fuel filter because it sounds like fuel starvation. But they are all clear. A buddy suggested new plugs, but they are relatively new and look OK if a little blackened.

I really have no idea where to turn next. Any suggestion to put me in the right direction will be helpfull. Honestly this is 2 years of farting around with this boat (and $1800 of repairs and 5 months in the shop) and it has hardly ever run well. truly thinking of parking it and walking away

 

[2x2smoke]

Drain fuel tank completely to make sure there isn't water in the system. If you find water in the tank, replace your filters. Check and dry all your electrical connector that might have been submerged, refresh your grounding connections on the motor. Do a compression test and replace your spark plugs

To check your fuel delivery:

Get some clear fuel line and attach it at the carb fuel return line

Fuel selector on:
try blowing into it, you shouldn't be able to blow back through the system.
apply suction, you should get pure fuel flowing out, no air

Fuel selector off:
apply suction, nothing should flow, no air, no fuel

get a clear jug and stick the clear line into it, start engine
(fuel selector on) and watch for fuel flowing out of carbs into jug. Nice steady stream of fuel, no air bubbles

you could also put test line onto fuel pump nipple, it should be air tight under pressure or suction, (i think)