Help with 90hp Merc Sport Jet please

[motv8tr]

Ok we have been having a lot of problems with our 1994 sea rayder boat. As the title states it's a 90hp Merc SportJet. We have taken it to the marina a couple of times, had their mechanic out for a ride in it, they can't seem to find the problem and the last time they had it they hooked something up wrong and it wouldn't start up at all...sheesh...very frustrating to say the least. <br /><br />Here is what I know...we take the boat out...starts up no problems and runs great for anywhere from 1-3 hrs depending on how hard you're driving.Once we start hitting rough waters or the kids jump the waves...it conks out. Normally it will start up again right away, then you have to nurse it back in or it will continue to give you problems. We have ruled out problems in the air and gas lines and thought maybe an electrical short of some kind. I also thought it might be overheating, but would it start right up again if that were the case?<br /><br />We took it out for a spin last night around 10 on GB and had to run it at a high speed and bounce it around for almost an hour then it kicked out. We then looked to see if there was any sparking when restarting it...three times we got it to conk out, three times it started right up again. the engine sounds really rough to me like it's not running right, but then I'm not too familiar with what a boat motor should sound like so I'm not much good in this area. <br /><br />If any of you have any suggestions on what we might look for or try that would be appreciated. <br /><br />Anyway, thanks for any help or suggestions... <br /><br />Maureen

 

[WillyBWright]

Re: Help with 90hp Merc Sport Jet please

Welcome to iboats and check your grounds.<br /><br />A lot of really weird ignition problems can be traced to corroded connections, mostly ground connections. Most are connected to the block in various places. Blocks are bolted together with gaskets, sealers, and loctite. Blocks aren't always the best grounds available. I have run jumpers between grounds to solve problems on several occasions. Might be worth a try. A dozen crimp connectors and a few feet of black wire can go a long way.

 

[funpilot]

Re: Help with 90hp Merc Sport Jet please

These boat motors are notorius for corroded and failed electronics. Before I speculate on what might be wrong, I'd like to mention that storage of the boat with a wet engine compartment is asking for electronic problems. Crack your cover open to let it breath between uses.<br /><br />There is a really good trouble shooting guide at http://www.geocities.com/kenimpzoom/SportJetIgntests.htm written by a very knowledgable member here, Kenimpzoom. Take a look at it.<br /><br />One thing that is really easy to try is to eliminate the rev limiter as a souce of problem. Disconnect the black and yellow lead from the rev limiter and run the boat. (the rev limiter is that flat, about 2 inch square electronic box on the starboard side of the engine, forward of the switch box). Be careful to watch the throttle so you don't over rev when you shoot out of the hole or jump the wake. If your engine runs well, just replace the rev limiter.<br /><br />Good luck,<br />fp