SportJet 90 lower carb issue

[staceyfukui]

I have a 1994 Bayliner Jazz with a 3 cyl. 90hp Merc SportJet. I was able to get it started but it seems like it's only running on 2 cylinders. There are three vertical carbs opposite of the engine side, the bottom carb is leaking fuel and it seems as though the float is stuck. I can move the float but it seems as though it gunked up and won't adjust on it's own. I can get a spark from the plugs but when they are all in the bottom plug gets flooded and won't start. The motor seems fine and runs great but I'm having this issue with the lower carb. Do I need to rebuild the carb or is there something else I can try before completely tearing it apart to rebuild.

 

[jerryjerry05]

Re: SportJet 90 lower carb issue

???? You can move the float???If you haven't taken it apart how?
REmove the plugs and do a compression/spark test. If it's loading up on gas/oil the needle might be stuck,take the carb off and check the needle/seat. Make sure it's not stuck open.
Excessive fuel leaking can also be a fuelpump diaphram problem.J

 

[staceyfukui]

Re: SportJet 90 lower carb issue

???? You can move the float???If you haven't taken it apart how?
REmove the plugs and do a compression/spark test. If it's loading up on gas/oil the needle might be stuck,take the carb off and check the needle/seat. Make sure it's not stuck open.
Excessive fuel leaking can also be a fuelpump diaphram problem.J

I took the bowl off of the bottom carb and was able to use my finger and move the float. We were able to do a spark test and was able to get a spark from all three plugs, we even replaced them to make sure. How bad is it to take just the carb off? We were working on this with it all still on the boat.

 

[kend301]

Re: SportJet 90 lower carb issue

Stacey ,
You need to pull all 3 carbs it is the easiest way , these things have vents on the starboard side of the carbs that get clogged and will gunk up all the carbs . No need for a major rebuild , Pull the carbs remove the bowls and clean the vent tubes , fittings , Needle and seat , and as Jerry suggested run a compression test as blow by will cause this.

 

[staceyfukui]

Re: SportJet 90 lower carb issue

Great! Thanks for the help. It'll take a couple days to get to it but after I do I'll post and let you know how it went. Thanks again!

 

[staceyfukui]

Re: SportJet 90 lower carb issue

There was a blockage in the vent tube for the bottom carb. The other two had a little debris but was easy to blow out. We did change the seals and the needle and seat. Seems to be running good now and no more fuel leaking. We did do a compression test and the top was 125 with the middle and bottom at 140.

 

[marcd101]

Re: SportJet 90 lower carb issue

Stacey,

Thank you very much for posting this issue. I was tinkering with my sportjet for 2 days and was ready to load it up and take it into the marina when I read this post. The next day, I discovered that my vent tubes were plugged. After these were cleared, the engine started easily and ran well.

Kend301, thanks for all of your feedback across this forum. It has been a terrific resource.

 

[kend301]

Re: SportJet 90 lower carb issue

Your Compression readings are perfect , not unusual for the top cylinder to be 10-15 psi lower , Enjoy the boating season !