Mercury sport jet 90 won't start when warm

nathan20328

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Joined
Jul 7, 2008
Messages
5
I have a 1994 Regal Rush jetboat with a Mercury Sport Jet 90 in it. We put the boat in the water two weeks ago (my friend started it while I was parking the trailer and it stalled before I got back there). I spent about 15 minutes cranking it and then the starter bit the big one. Friday my local marine dealer got the starter in (300 bucks!) and I installed it and put the boat in the water Saturday. Started right up, ran rough but seemed to get better as I ran it. I did note that when I turned a tight corner, it would almost die. It is almost all fresh 50:1 fuel plus a can of seafoam for good measure. Took it out of the water and was pretty damn happy even though my wallet was a lot lighter. Next day, put the boat in, and ran it for a bit (still rough but seemed pretty decent once warmed up), then went over and docked it next to my pontoon boat. Came down to take both boats over to the beach (Indian Lake in Ohio) and the motor turned over but refused to fire whatsoever. Finally gave up on it and took the pontoon boat to the beach. A sidenote: the pontoon boat battery died at the beach and I had to get a ride to get a new battery for it...HAH! Anyhow, ended up towing the dead jetboat with the pontoon boat to get it to the landing and on dry land. To finish my sad, sad story, the bottom two of the three spark plugs appear to be dry even after cranking for 50 years...do I have a fuel pump/diaphragm issue? I'm going to go through the ignition test this weekend but before that I'd like to test for fuel delivery...thanks for listening:)
 

JUSTINTIME

Captain
Joined
Sep 2, 2006
Messages
3,284
Re: Mercury sport jet 90 won't start when warm

better test in volts with a dva
 

nathan20328

Recruit
Joined
Jul 7, 2008
Messages
5
Re: Mercury sport jet 90 won't start when warm

Thanks. I printed out the kenimpzoom test sheet and will try that. Is there an easy fool-proof way to verify fuel delivery...the dry spark plugs make me think that might be the issue?
 
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