View Full Version : Running rich on top end

05-22-10, 03:28 AM
I have the 2004 polaris jet boat with the optimax 250 anything over 3000 rpm runs rich, bad gas mileage takes 10 sec to plane wont get over 35 miles per hour wide open at 6800 rpms. Feels like a cylinder drops off on top end. Wake boarding behind the drivers side exaust has alot of smoke. Boat shop claimed to check out fine on computer and plugs look great. (I don't think they ever had them out) but they think its a coil problem. Any suggestions would be great. working on the opti is a new animal for me.

Dr Honda
05-22-10, 09:02 AM
There are a few things against you right now. (Polaris isn't it)

first... the Merc engines were only used a few years in seadoo, and in general, we don't know much about them.

second... when dealing with fuel injection... you need a dealers computer to figure out what's going on.

Just some thoughts...

If it's running rich, but will idle... that rules out an injector that's hanging open. although, at higher duty cycles, it may not be sealing, or closing fast enough. If it gets up to 6500 rpm... that rules out an electrical issue. You would have to fire all plugs to get up to max RPM's.

If you were truly running excessively rich... you would be fouling plugs quickly since you are a 2-stroke. If possible, please post a pic of your plugs.

Your speed and slow acceleration issue is probably a separate problem since you are getting to 6500 rpm's. You should check your impeller, and wear ring. The spec for a sport jet drive is 0.018"-0.052"... but the tighter the better.

Last thing... if you join this forum ($10) you can down load the Merc manual, and it may help in your search for answers.

05-22-10, 12:03 PM
Thanks tony. I will pull the plugs today and take a look. I thought that the wear ring was part of the problem so I had a stainless steel wear ring put in and the impellar tuned. 2 years ago a boat shop said I had a coil out and replaced it. I just can't figire it out. Boat runs like it is totally normal just no real power on top end and is pouring out oil exaust. The best way to descibe it is the boat feels like it drops off a cylinder with any kind of load. Yeah I will join the form thats the least I could do for the help. Thanks.