Merc Sport Jet (Rebuild?)

[cybercolt]

Ok, I got spoiled by my first boat (Cobalt CS23). So My second Boat (a bit smaller at 14 feet and a whole lot cheeper). It's got a sport jet 90 in it. I went throught the Red Stater mix up and had to replace a switch box. Things are going fine for a few weeks now. Tonight I take it out and had one hell of a time starting the thing up. The engine is running rough and performance is way down. It looks like there is white smoke comming from the Exaust (I was thinking heads are blown). Does any one out there know what is going on with this thing? Should I rebuild or Replace with a 120 or 175?<br /><br />Thanks,<br /><br />Jason

 

[hondon]

Re: Merc Sport Jet (Rebuild?)

If you have gotten a little agresssive on the flusher ,this can cause water ingestion on these units.Now here is what you probably don't wanna hear.From my observations that sportjet 90 was too underpowered for all of the applications I have seen it installed in.120,s not much better. BOTH used a traditional FORCE powerhead and just skroll down the board about those.Swapping to a 175 will require a complete repower. jet up.Do a compression test on the engine you have and inspect the plugs for water.Also check your fuel system and consider an inboard safe primmer.

 

[cybercolt]

Re: Merc Sport Jet (Rebuild?)

I checked the plugs and they seem to look ok. I will need to find a mechanic to check the compression on engine, unless someone knows of a cheep compression checker that I can buy. I do know that all 3 plugs are fireing. However, the engine is really rough. At an idle it looks like it will vibrate it's self apart! Vibration is shakeing the whole boat at any speed!<br /><br />Thanks<br /><br />Jason

 

[hondon]

Re: Merc Sport Jet (Rebuild?)

Here's another little thing. These things are equipped with a rev limiter and if that is malfuctioning ,could cause your symtoms.The type of plugs you are using can leak R.F.interferance to that unit as well.Run NGK with a Z in the plug number.Believe yours to be BZUHW 2 but double check this. Do the comp. check .We're shotgunning now.

 

[page62]

Re: Merc Sport Jet (Rebuild?)

Some auto parts stores will lend you a compression checker free of charge. But they're cheap to buy -- about 20 bucks.

 

[cybercolt]

Re: Merc Sport Jet (Rebuild?)

Thank You, I will have to run out and get one on pay day! I planned to get new plugs then as well!

 

[cybercolt]

Re: Merc Sport Jet (Rebuild?)

Ok, I got the compression gague. I have 115-117 top, 120-125 middle, and 120-122 bottom.

 

[cybercolt]

Re: Merc Sport Jet (Rebuild?)

Ok Found out that I have the wrong plugs. The Boat came with BUHW not BUZHW. Got Some ordered. Hope it works.<br /><br />Thanks,<br /><br />Jason