MERCURY SPORT JET 90 HP TOO SLOW

[ODDD1]

Re: MERCURY SPORT JET 90 HP TOO SLOW

Yes rich..those are the bolts I am talkin about...if you look at your ride plate, you will see a notch in the side flanges where the plate is supposed to bend to change the trim....be gentle...add a washer at a time to check effect...

 

[RICHRICH26]

Re: MERCURY SPORT JET 90 HP TOO SLOW

ODDD1, You are exactly right, thank you very much for your help. Will a 1/8" washer make very much difference???

 

[Ledif7]

Re: MERCURY SPORT JET 90 HP TOO SLOW

did the boat run faster after the trim adjusment?

 

[RICHRICH26]

Re: MERCURY SPORT JET 90 HP TOO SLOW

No it did not. I am at a loss and at wits end. I am still doing about 5 mph. Let me go over what I have done so far maybe there is someone with the "magic fix" Carbs rebuilt, new ride plate gasket, new plugs, new gas, .032" clearance between impeller and housing, impeller good no nicks, 4500 rpm at w.o.t., add spacers to trim 1/4 total, 1 person in boat, and every other minor check. If there is someone with even a slight idea I will be more than happy to hear it.

 

[clanton]

Re: MERCURY SPORT JET 90 HP TOO SLOW

Led. Are you close to Citrus county.

 

[pmpiper@hotmail.com]

Re: MERCURY SPORT JET 90 HP TOO SLOW

I haven't worked on a jet drive but it doesn't need a leak in something to cavitate. Are you sure the water inlet is clear?

 

[RICHRICH26]

Re: MERCURY SPORT JET 90 HP TOO SLOW

that was the first thing I checked

 

[Thena]

Re: MERCURY SPORT JET 90 HP TOO SLOW

I recently had a sportjet 90hp engine rebuilt for a 152 donzi medallion.<br /><br />The Engines seems to work fine but the boat seems to have a hard time to plane and when it does it runs at 20-25mph. <br /><br />I've checked the impeler and it is in perfect condition. There is nothing blocking the way. What could be wrong??<br /><br />I've run out of ideas.

 

[russthemuss]

Re: MERCURY SPORT JET 90 HP TOO SLOW

Geee ,Check your running the right spec impellor for the engine.Has it ever run well? 4500rpm seems a bit low but i dont know your specs.Is the hull full of water!! Check the thread on the shaft at the coupling.Check the coupling,check the impellor drive.Pull it all apart!

 

[scottconsoli]

Re: MERCURY SPORT JET 90 HP TOO SLOW

have you tried the stator assembly, i had the same problem

 

[Crater]

Re: MERCURY SPORT JET 90 HP TOO SLOW

My sp90 specs rpms between 4800-5300 at WOT I've also seen specs say between 5000-5300 so I think your rpms are low.
That being said my sp90 on a 18' Tracker seems to run slower than I think it should also 25avg WOT on Gps 30mph top on glass water running down stream.
I am curious about the ride plate adjustment also. How far did you bent and shim yours down?

 

[chadstan]

Re: MERCURY SPORT JET 90 HP TOO SLOW

Yes rich, ride plate gasket/ ride plate itself will cause this...have seen many ride plates 'sneezed' off the bottom of the pump by people starting them up out of water...recheck all fasteners on the plate, caulk the gasket to eliminate any leaks between plate an hull, it has to be a PERFECT water tight seal....

do you know how long you can let them run out of the water? thanks