Force 90 (SportJet-90)

[InDaDark]

I purchased a 1994 Donzi JetBoat that was stored for over 6 years. After new fuel and battery, the engine started fine and idled great. While out of the water, the engine would rev up to high speed. (No Load) In the water, the engine will not rev up to full speed. (No Tach..estimated 2500-3000 RPM)The engine has New Plugs,and does not have a miss. I'm wondering if this could be a timing problem. This condition occures only when the engine has a load on it. My last post was put in the I/O section, but this is an outboard powerhead, on a jet....right? Any information would be appreciated. The stator is *red*..if that matters? My email is lindy1@comcast.net.

 

[roscoe]

Re: Force 90 (SportJet-90)

Low compression?<br />stuck rings? - decarb<br />weak spark to one or more plugs?<br />weak fuel pump?

 

[InDaDark]

Re: Force 90 (SportJet-90)

Update: Compression is #1-132/#2-129/ #3-133. What/how do I check for a strong spark? All 3 plugs are sparking....bold blue? Fuel Filter is new. Fuel Pump seems to be pumping steady stream of fuel. This problem is only under a load. I have never worked on a 2 cycle engine/outboard. I wish it had a chevy engine...

 

[wakataka]

Re: Force 90 (SportJet-90)

They make 4 different sizes of main jets for the carbs on these engines. If the boat was set up for a different altitude than you are running it at, it could be either too rich or too lean.

 

[roscoe]

Re: Force 90 (SportJet-90)

It could be a rich/lean situation as Row indicated. It could be fuel starvation. Does the bulb in the fuel line stay firm, or go flat when running? What happens if you choke it while it is running at high speed? If the bulb goes flat, what happens if you try to pump it up at high rpm? If you have a strong spark, it should jump a 7/16 inch gap.

 

[InDaDark]

Re: Force 90 (SportJet-90)

I'm thinking the same thing as you guys. The boat sat for over 6 yrs..and never winterized. I'm thinking about rebuilding the carbs. The boat does not have a squeeze bulb on the fuel line. Goes fuel line goes from the tank to the pump. When I choke the engine at WOT...it dies. The engine is a Sport-Jet 90. I did check the pump screen, and it was clean. Might go ahead and change the fuel pump also. I dont think sitting for 6 yrs did the boat any good. The previous owner did not even winterize or drain the gas. (I drained the fuel and cleaned the tank) While I have the carbs apart, should I change the jet size? I'm in Michigan. Don't think the altitude has anything to do with it. The boat was from this area, and ran fine when it was new.