Two blown engines...Need some advice.

[shocker]

I bought my 97 challenger used with the 787 engine. With barely a half tank of gas gone I lost a cylinder. I get a new engine from SBT and rebuild the carbs, set to factory specs. Wthin 10 minutes of break in, I lose the same cylinder. SBT's analysis says improper break in. I'm notbuying that because I was following their procedure. I spoke to a tech and tell him the same cylinder on both engines failed. He tells me that even with a carb rebuild there is no guarantee the carbs are fine. For what it's worth, the plugs on the new engine looked great, a nice chocolate color. We also did the block-off and are now using premix at 40:1 as reccommended. According to my mechanic, the only adjustment not made to the carbs was checking the pop-off pressure because he did not have that tool. He said we used the same spring and it should not have mattered. Does this still sound like a carbs issue? I've been reading threads until my eyes bleed and hear the rear carbs like to go lean as the get older. My new engine is on it's way and I want to make sure this doesn't happen again.

[dsolie]

Re: Two blown engines...Need some advice.

could very well be carb related.. Pop off pressure is extremely important in delivering the right amount of fuel at the right time.

But, hell, you got a warranty anyhow.

[shocker]

Re: Three blown engines...Need some advice.

Make that 3 blown engines. No, I'm not really having fun. Once again, I followed break in procedure religiously. I was up to the 50% throttle point of break in. I was constantly checking plugs at cooling points and they looked fine. Last time out I idled about 10 minutes through wakezone and as I slowly accelerated to 50% throttle...Boom. Get towed in and find mag cylinder at 120psi. I pulled engine once again and see scoring on piston. Carbs went to seadoo and I had them go back over them and they set pop off pressures and double checked everything else. All should have been well. I did not get an overheat beep. I know it works because we tested it and the sticker did not change color either. I don't know what else to do. Someone told me to check clearance between rotary valve and cover. With the old engine I was able to get .024 feeler guage in there with oring. I just read on here that you should check without oring. I cant check now because engine is boxed up and ready to head back to SBT. The cover and valve have usual light scratches but doesn't seem to be to bad. From what I read clearance issues will typically create hard starting. The boat always started great. Can a clearance issue cause a lean or hot running condition and cause an engine seizure? This will probably be my last engine because I am out of warranty time in a few weeks. I'm still deciding on whether or not to keep the boat after new engine is back in. What else can I check??? The frustration is beyond what you can imagine.

thanks

[dsolie]

Re: Three blown engines...Need some advice.

What has SBT accounted the other two failures too?

[shocker]

Re: Three blown engines...Need some advice.

What has SBT accounted the other two failures too?

The engine that was in the boat when I bought it failed from detonation. The first new engine from SBT they told me improper break in, which I stated above I find hard to believe considering I followed their instructions thoroughly. This second new engine is on its way out of here today and I'll wait to see what they have to say.

[nmpeter]

Re: Two blown engines...Need some advice.

I'd be checking the rotary valve cover/intake manifold for an air leak, just to be on the safe side richen up the mixture a bit on low speed adjuster, did you personally eyeball the low speed needles? Sometimes it takes a seasoned pro to spot a carb problem. Seeing how much trouble this has been, have you thought about tossing in good money after bad and just buying two new carbs? Pulling engines from the boat has got to be wearing thin at this point.

[shocker]

Re: Two blown engines...Need some advice.

SBT says this latest engine had a "4 corner seizure"? They said it didn't go lean and the oil lines looked good. He also said it could be possibly improper break-in or it got hot. I'm shooting down the improper break-in theory again because I followed their guidelines thoroughly. My overheat sensor works because we tested it after the first engine went. On this down time I have since blown out all cooling and fuel lines and removed old fuel. I'm no carb guru but I asked my mechanic how the needles looked and he said they looked fine. Seadoo must have thought so too because they did not make any note of them being bad. I've been thinking this has been a 99% a fuel/carb problem but maybe it isn't. Can the engine get warm enough to seize and not give off a warning beep? I have flushed out and cleaned cooling channels in exhaust and manifold as well. Is my cooling system not flowing enough water? Could an air leak in the rotary valve cover cause an overheat condition and engine seizure? I'm out of warranty time with this being the last engine and yes, I am tired of swapping out engines. I've done all I know to do and what I've been told but have not yet found a "smoking gun" as to what really is going on.

[Dutchy]

Re: Two blown engines...Need some advice.

Hello,

If I were you i would be going to check up my crankcases. The temp sensor is not placed inside of the combustion chamber, but in the outer casing of the engine. So it can not feel what goed on inside the eninge. If you have a leak someware you can get problems like this.

I have had an by me build custom engine, for the dutch championchip pocketbikeing. I build an puch maxi engine, with an KTM membrane, custom inlet e.c. It run smoothly for a period of time but later I was racing and it ran perfect, but a few moments later it started to run bad. I let it cool and it was perfect again, later on it ran really bad again.

I found out that I had fine hair thick cracks in the crankcases. Which let air trough when the engine expands due to the heat.

You could be having the same kind of thing going on here. When I don't trust an engine I seal it with liqued gasget (A)

Greetings from Holland!

[Technical Support]

Re: Two blown engines...Need some advice.

What color fuel lines are on the ski? And pull your fuel selector (on/off/reserve) valve out and see if there is any blackish greenish crap in the ports.

[shocker]

Re: Two blown engines...Need some advice.

Fuel lines are the original black ones. I just got off the phone with a tech to get a little more info and now feel more confused. lol I was thinking of using and aftermarket temp gauge to monitor temps. He said the problem with that is you could still have cool head temps but not know the cylinder temps. Makes sense and rules out cooling system maybe? He said engine could have gotten lube but still starving for fuel causing cylinder to overheat. Looks like I'm maybe still having carb issues?

[Dutchy]

Re: Two blown engines...Need some advice.

told you that temps may vary between cumbustion chamber and the cooling system itselve.

I would check for leaks in the crankcasing e.c. and clean the entire feul system.

A cool trick is to get or make engine coverplates for the inlet and outlet and then you can put pressure on the engine and that way you can find leaks... Thing here is, that when the leaks are super super tiny that they may only be seen when the crankcase is hot ( so it expands ).

SBT probbely knows what I mean.

Goodluck