merc sportjet top cylinder doesn't always run?

[jprice]

I'm looking to possibly buy a 94 bayliner reflexx with the mercury 90hp sportjet engine.

The owner has told me that the way these engines work is that the top cylinder doesn't fire until the engine gets above 600rpm, but that's how these engines were designed.
Because of this, only the bottom 2 cylinders work during startup, and if the bottom one gets flooded (which is supposedly what happened when he was trying to start it for me) then it won't start.

Is this true? Are these engines really designed this way to have the top cylinder not always fire? Are they prone to not starting because of the bottom cylinder flooding?
Or is he just full of crap?

 

[indy440]

Re: merc sportjet top cylinder doesn't always run?

He is full of crap. All three should fire. I used to have the same motor in a 96 SeaRayder. They were prone to ignition failure. Does yours have the red stator update?

Do a compression test!!!!!!! (cant stress how important this is especially if you have a cylinder that doesnt fire at idle)

They also had an issue with the reeds sticking and/or breaking, and also rings sticking from carbon build-up when burning cheap oil. Any one of these issues could cause that cylinder to not fire at idle but then pick back up again.

If its flooding one of the cylinders the carbs should probably be rebuilt. These are tricky carbs and you have to drill out a few welch plugs to get everything clean... Maybe you can avoid this if you soak them or have an ultrasonic cleaner and patience... I have neither.


The sportjet 90 motors have a bad reputation, but I had one and loved it.

 

[jprice]

Re: merc sportjet top cylinder doesn't always run?

Thanks indy, I appreciate it.

He seemed like an honest guy, and who knows, maybe the previous owner told him that, and he actually believed it. Or he could be a bulls**ter and just trying to unload a problem.

Right now my gut is telling me to steer clear.

This weekend I'm going to take a look at a 97 Sunbird Sizzler. Hopefully that one turns out to be in decent shape.

Thanks again.

 

[indy440]

Re: merc sportjet top cylinder doesn't always run?

where is it and how much are they asking? I didnt mean to turn you off to the boat altogether, if its nice and cheap then it may be worth it. I really loved mine when it was running properly.

 

[jprice]

Re: merc sportjet top cylinder doesn't always run?

you didn't turn me off from it completely, i was already starting to feel reservations when driving home last night from seeing it. you just helped push me over the edge.

Seriously though, unless I can get a mechanic to check it out and tell me that the engine is in good shape, i'm not messing with it.

He's asking $2200, and it's not far from me here in Marietta, GA.

 

[indy440]

Re: merc sportjet top cylinder doesn't always run?

i sold my 96 searayder five years ago for 2500. They were very similar boats.