Sportjet 90 hatd start

[Teeko]

Hey guys, I've been reading all the posts I can find about the hard to start sportjet (force/chrysler) motors. Here's what I know for sure...
Used to start up great.
Became sluggish to turn over and hard to start.
I have new plugs in it, new fuel filter, new battery.
Lately it was very difficult to start, backfiring etc.
Figured I had a bad inlet needle as when I primed the bulb, fuel was puking out of the middle carb throat. To be sure, I changed all 3 inlet needles. Carbs are spic and span.
I got the flush fitting so I can start it on the driveway.
Today, after putting the carbs back on, it would fire right up and immediately idle beautifully.
When I put it in the lake, it would barely crank. Seemed like the battery was dead, but wasn't. Sometimes it turns over super fast and other times it barely turns, like the compression is too much or something. I can hear a sort of hiss from time to time from what I think is the top cylinder.
I'm wondering if there's a bad head gasket. Finally got it running and cruised the lake at 41mph. Throttle response seems alright, jumping on plane pretty easily. Shut the motor off and same scenario. Barely turns over. When out of the water, fired right back up. Seems when the jet pump is in the water/motor under load, I get that hiss/backfire sometimes.
I'll do a compression test tomorrow and report back. Just not sure why, if it is a bad gasket, it turns over so laboriously. I'm also wondering if somehow the timing is out. Maybe too advanced, causing it to fire too early. Not super educated when it comes to timing and electrical.

The boat is a 95 but the motor has a tag from quicksilver remanufacturing with a dec 05 date stamp.
Thanks from your friendly neighbor north of the border.

 

[tdonoughue]

Almost sounds like the timing is off. Like when it is in the right spot, it starts fine, but when not it gets hung up. Not familiar with the ignition system on your boat... But whatever it is, can you check that?

 

[Teeko]

Almost sounds like the timing is off. Like when it is in the right spot, it starts fine, but when not it gets hung up. Not familiar with the ignition system on your boat... But whatever it is, can you check that?

I'll borrow a timing light from a friend. I'm not sure why it turns over fine one second but then doesn't the next.

 

[tdonoughue]

Yes, I agree that is pretty confusing. The only reason I think timing is a) it is easy to check and b) if you were firing at a different place in the cycle, you might get different results depending on where you start cranking. I'll admit it is a long shot, but it is easy to check...

 

[Teeko]

Yes, I agree that is pretty confusing. The only reason I think timing is a) it is easy to check and b) if you were firing at a different place in the cycle, you might get different results depending on where you start cranking. I'll admit it is a long shot, but it is easy to check...

I just checked compression. 132, 135, 132psi. Pretty consistent between the 3. I might have to go get a timing light and see how far off my base time is. Not sure why or how it would go out but I think the compression sort of rules out a bad head gasket??

 

[RedBarron55]

Try a starter.
If the engine does not spin about 300 rpm on the starter the magneto won;t fire. Try the timing light on the start and see if it flashes on the first turn over compression.
By the way the Chinese starters are crap, but cheap and over priced even then.
If you a starter shop in town take it to them and have it checked and rebuilt.
It is possible that you are getting water into the bottom cylinder as well, but it would do that on the hose (the hose that comes from the pump to the bottom of the exhaust manifold, not the flush line on the top of the engine. If you pull the #3 plug an turn it over and water come out that is a clue. The starter will not turn the motor with water in the cylinder

 

[Teeko]

I bought a timing light and from what I could gather, it was reading 0° at idle. I moved the screw on the adjuster and got the timing light to hit at 8° which is what the book says but to be honest, I'm not sure if its btdc or after. Not really sure of what I'm doing....
My solution is to put a dot of red paint at the 8° mark and retest to see if I went the right way. Still no start in the water but now I think my battery is low. Never thought about the starter going bad. Got the battery on charge now so we'll see what happens.

 

[Teeko]

So here's my flywheel. 4 of 6 magnets have come loose. I think I caught it before it did any damage to the stator. I've read numerous threads on this issue and guys replacing flywheels. Some people have swapped to the "red" stator, some have replaced the cdi box to something else. Not sure if anyone has any insight on this but any help would be appreciated. The flywheel is out of production.
Got quoted 960CAD for an aftermarket one and I'd be willing to pull the trigger if I knew 100% that it would work and I wouldn't need to replace the cdi or swap to the red stator.
Many of the posts I've read are 8 years old.

 

[tdonoughue]

Ok, again, I don't have this engine and have never worked on one. But, from what I have read and some thoughts...
1) I don't see any damage to the stator, so you might have dodged a bullet there. How, I do not know...
2) If I recall correctly the 'red' stator upgrade was more recent and replaced the 'black' stators. The black stators did not need a little box; the red stators add a little red box, presumably to translate the 'red' stator signals to 'black' ones.
3) Your magnets don't look as bad as some I have seen. I wonder (openly) how the magnets were attached in the first place. Epoxy? I don't think they could tack weld them, could they? At any rate, is reattachment an option? Obviously not without its risks, as well (if they come off, your stator might not be so lucky next time).

 

[mitchjet]

I'll borrow a timing light from a friend. I'm not sure why it turns over fine one second but then doesn't the next.

Hi, i am new here. i have small donzi with a sportjet 90 . Before i blew the engine and replaced with a Yamaha power head 115 i work a lot on the ignition and my main issue was the magnets on the flywheel. After trying different ways to attach them i ended casting a solid epoxy ring with the magnets and then my piston number 2 crack. i still have the flywheel if you need it. i am in jacksonville florida .

 

[Teeko]

Hi, i am new here. i have small donzi with a sportjet 90 . Before i blew the engine and replaced with a Yamaha power head 115 i work a lot on the ignition and my main issue was the magnets on the flywheel. After trying different ways to attach them i ended casting a solid epoxy ring with the magnets and then my piston number 2 crack. i still have the flywheel if you need it. i am in jacksonville florida .

I epoxied my magnets and the boat is running now. Thanks though.