6 replies to this topic

[turnerr]

Has anyone had any problems with the Optimax 250 missing? It seems ignition related so I replaced the billion dollar spark plugs - no joy. I spent some time digging around different usenet groups but couldn't find any Doo'ers that did much of their own work. Found some info on a Mercury outboard user site - all the problem descriptions I found that came close to what I'm seeing were all plug related - they (mostly offshore fisherman) are a pretty divided group about the engine (if you didn't know, the reason the engine is mounted vertically in the seadoo is because its the power head of the Mercury Optimax series of outboard engines). At any rate, I changed the plugs with no luck so now I'm going to start simply and work my way up (fuel filter, fuel lines, injectors, ignition/coils). My main problem is that it's really hard for me to work on the boat at home as it's on a custom trailer with a hydraulic jet ski lift on top that prevents the rear deck from opening very far - I have to climb into one of the compartments next to the engine and remove the side covers from inside... The engine idles and runs fine, but when I bring it up to more than about 4K rpm it starts missing badly. If anyone has had a similar problem, I'd appreciate hearing about it...

[nookie201]

Hi,

I think fuel filter and injectors would be what I would check after the plugs.
I would also run some fuel injection cleaner through (unless mercury advises against it).

Sounds elementry, but have you tried gas from a different station ?.

They also have a tech support line, I've talked to them, maybe they can give you a hint of what it could be.

 

[turnerr]

Hi,

I think fuel filter and injectors would be what I would check after the plugs.
I would also run some fuel injection cleaner through (unless mercury advises against it).

Sounds elementry, but have you tried gas from a different station ?.

They also have a tech support line, I've talked to them, maybe they can give you a hint of what it could be.

-Gab

Thanks for the reply! Yeah, that's the route I'm headed down. I just checked the vent line check valve and the feed line from the tank. The first inline filter checks good but from there it goes into a series of separators (water, then vapor). There is pressure at the injector rail, but without the manual, I have no idea what the pressure is supposed to be (it idles and runs fine, the missing doesn't start until much higher rpm). You wouldn't have downloaded the Mercury manual before the webmaster was threatened would you? As for fuel quality, given the problems, I don't think that's an issue, but I have since treated the tank with an anti-water additive. Do you have the number for the tech support line? Is it Mercury or SeaDoo? One thing I'm interested in is the purpose of the air injection system (the filter is pretty crudded up). I also found a bit of moisture and oil/grease in the intake system both up and down stream of the throttle body/butterfly with no clear idea of how it would have gotten there...

[nookie201]

Hey, I got their phone number from their web-site.
Did you also check air-hoses, no kinks or flat spots ?.

If you post your email, someone can maybe sent you some file.


 

[turnerr]

Hoses all look brand new, no kinks or dry rot. If the manual showed up in my inbox I would be most grateful and silent....

rob.turner@navy.mil

[tiggerman]

Hoses all look brand new, no kinks or dry rot.  If the manual showed up in my inbox I would be most grateful and silent....

rob.turner@navy.mil

Have you thought about your Merc being REV-LIMITED? The Rotax powered boats are rev-limited @3500-4000 RPM while the shifter is in the N position, for safety. Keeps you from grenading stuff.
I would assume that the Mercury crafts are rev limited as well. You mentioned you had the boat at home on the trailer. It idles and runs fine but when you raise the RPM to around 4K it starts cutting out. Try this with the FNR lever in F and see if it cuts out.
I am also assuming you have cooling water running while cranked. If you can successfully run at higher RPMS, then it appears the limiter is doing it's job and you are good to go.

[turnerr]

Thanks for the reply, but no it's not a rev limit issue. The Mercury powered boats have single lever controls. This problem happens in the water...