Just rebuilt sportjet, hard starts.... fouling plugs

OK, just rebuild my 90HP sportjet. Seems to start hard and is fouling out plugs.

I AM running double oil, perhaps that is the cause for both? Perhaps timing?

Once it got started, it would move great! But now, after about 5 hours or so on the engine, I'll be moving along nicely and it will quite out on me.

It will fire right back up......... but when I go to give it gas it dies out.

Any ideas? I'm having a hard time even finding someone that I can PAY to tune this thing properly........ My lack of knowledge in regards to tuning it, as well as I'm pretty much to the point where I just want it done.........

I'd gladly pay someone who KNOWS what they are doing, but the minute I call up any shops and tell them its a sport jet, forget it, "we don't work on them".

Phil

Re: Just rebuilt sportjet, hard starts.... fouling plugs

Are you using NGK spark plugs?
Dont use L76V Champion plugs...they sucks...use NGK

Ive also had a lot of troubles with this boat....
Many parts are not available anymore...like piston pins, flywheel, etc

Re: Just rebuilt sportjet, hard starts.... fouling plugs

Ya, I've tried a bunch of plugs. I'm using the equivalent NGK plugs right now....

Looking at the plugs, i'm thinking pre-ignition.........

Everything on the engine is new minus the electrical stuff........ a few flywheel magnets came off, so I re-epoxied them back on in place......... what would be a symptom of a magnet on backwards?

I'm still thinking its a carb / timing issue wtih my engine (hoping anyways).

I just wish all of these marinas woudlnt SHUN my boat the minute I tell them its a sportjet.... really, how is it so different? Same power head isnt it as an outboard.......

Re: Just rebuilt sportjet, hard starts.... fouling plugs

hckrphil said:

a few flywheel magnets came off, so I re-epoxied them back on in place......... what would be a symptom of a magnet on backwards?
.....

Click to expand...

the symptom will be irratic timing.
make sure that there is no cracks on any magnets.
If you do have some, you'll have to change the flywheel and it's no longer available
Also, dont put any grease on the center cone of the flywheel because it wont help to conduct. (if you do, there is a special grease for that)
and i'm not sure but it might be the same thing with epoxy to stick the magnets.

Re: Just rebuilt sportjet, hard starts.... fouling plugs

Well I can tell you that there is a crack in one of the magnets.........

When it is up and running, it seems to be running nice and strong.....

Re: Just rebuilt sportjet, hard starts.... fouling plugs

hckrphil said:

Well I can tell you that there is a crack in one of the magnets.........

When it is up and running, it seems to be running nice and strong.....

Click to expand...

A crack on the magnet will make irratic timing.
Instead of having a magnet like this + _______ - (+ in one end & - one the other end)
the crack will make it go like.....this +__- +__-
so the switch box will make the coils to spark twice. (it match with your idea of pre-ignition)
Dont go any further on your search and try to find a flywheel