Sport jet 90 low power

[Juster89]

im new to the forum but have been reading great amounts of info over the years from this site.

ok here we go i bought this sea rayder about 2 weeks ago. took it out and ran it. it was very hard to start but had been sitting for a year or so. while running it the motor just seemed it lacked power and never got on plane id say it went maybe 8-10mph and maybe 4,000 rpm not shure on that. and at wot it smoked a lot more than i thought it should. i have a 3cly 50hp yamaha jet outboard that i compared the smoke to

i took it home and stared checking it out. i check the fuel it looked very dark guessing 25:1 - 30:1 so i drained the fuel and added fresh 50:1. cleaned all carbs. replaced the spark plugs with new. i found a bulliten that has a cross number to a new spark plug that takes the place of the flat head plugs. i installed them. ran boat again it starts great runns fine. but again same power problem and just sounds like the rpm is lower that it should be. i seen the factory specs somewhere and it was saying 5,500 rpm?
engine still smoked at WOT.

i checked the fire all looks good. i checked the compression. all cly's are within the 10% specs.

motor has the red stator.
engine almost sounds like it has a dead cly.
my 50hp yamaha had a loose spark plug wire that would come off every now and then and it would run on the other 2 cyl's but just not any power. the sport jet kinda sounds like that. but with a spark checker all is good.

at this point i am lost and in need of help and help would be great

thanks juster89

 

[Juster89]

Re: Sport jet 90 low power

i forgot to mention i checked the ride plate. it looks good.
it also had a new impeller and wear ring.

 

[kantush]

Re: Sport jet 90 low power

The ride plate has to be perfect. Even on both sides also check the reverse gate in full forward should be exposed by at least 75%

 

[Juster89]

Re: Sport jet 90 low power

reverse gate id fine i checked that. i will have to take a picture of the ride plate im not shure whats it suppopsed to look like.
i forgot to mention that when motor is hooked up to flush hose the motor revs just fine. so what ever is happening only does it under load
could the ride plate cause the engine to not rev completly? thanks

 

[calledinsick]

Re: Sport jet 90 low power

A couple of things.

What year engine?

I'm not familiar with a substitute plug unless it's a direct cross, should be (for 1995) Champion L76V or QL76V or (1996&97) Champion L77JC4 or QL77JC4.

What RPM (in the water) are you getting at full throttle?

Are you sure the Oil Injector is blocked off for premix?

Disconnet the Black/Yellow wire from the Rev-limiter (small 2X2" box on the starboard side of engine nearest the carbs) and try again.

Verify Firing Order- 1-2-3 is firing order but I don't have colors for wires handy...I think they're stated somewhere in this forum.

 

[Juster89]

Re: Sport jet 90 low power

The plugs are the L77jc4. I have not tacked the engine in the water yet. It's in a 94 sea rayder. The oil system I's eather blocked off or did not come with this motor. I will try the rev limiter later and check back. Thanks

 

[Juster89]

Re: Sport jet 90 low power

Ok heres the update. I looked at the ride plate looks good. And correct me if I'm wrong but if there was air/eghaust getting in the intake from the ride plate would the motor not rev like my other jet boat does? And I did the fuel pump test and with the hose unhooked from the bottom carb and engine cranking the fuel comes out in little bursts and in-between the bursts it's almost no fuel coming out. When the primer bulb I's squeezed while cranking it makes a solid stream out. Could the fuel pump be my problem? Thanks

 

[calledinsick]

Re: Sport jet 90 low power

FYI- For the 94 Sport Jet 90, I show L76V.

 

[Juster89]

Re: Sport jet 90 low power

I found this last week this I's why I used the l77jc4 plugs.

http://www.marinemechanic.com/merc/SPORTJET-90-UPDATE-EN_09.pdf

 

[calledinsick]

Re: Sport jet 90 low power

Nice! I'll add it to my list of resources! Thanks for the update!

 

[e-spin]

Re: Sport jet 90 low power

I just had the same issue, 94 sportjet 90, added a tach and could tell I was only getting 4200 rpms while plowing water the whole time with plenty of smoke. I did the carbs, fuel, fuel pump, plugs...finally after months, I checked the trigger assembly and found that although I had enough spark to arch through me to ground (ouch) it failed the resistance check by about 50% on that cylinder. I believe it should have had 80 ohms but only offered about 40 Ohms.(much different than the other two in any event) I replaced the trigger assy. and Rpm's now run about 5200, it gets on plane with two adults and will peak at about 36MPH with my gps. Ironically, it's harder to start after the repair. I'm saving that repair for another day. Good luck

e-spin

 

[Crater]

Re: Sport jet 90 low power

you bet, should be a nice steady stream. looks like a new diaframe. there cheap and available. either order online OR take yours to the marina store and they will be able to match it up. They used either a square type or round dual stage pump, so take the old diaframe with you. there like $3.00 and 5 min of work

 

[Juster89]

Re: Sport jet 90 low power

I was thinking it might have been a trigger problem. Does anyone know the proper technique for checking the trigger? Thanks

 

[Crater]

Re: Sport jet 90 low power

Trigger:
Set multimeter to Rx100
1100-1400 ohms on a cold engine. Ohms will increase if engine is warm
Brown to white/black =
white to violet =

Post results for help

 

[Crater]

Re: Sport jet 90 low power

Your fuel pump is shot if it is surging. This surge could cause a lean burn even then bad things happen. BOOM or in my case you'll not hear anything and start scratching everthing you got wonderering what the he** happened.

 

[calledinsick]

Re: Sport jet 90 low power

If the fuel flow is pulsing while cranking replace the diaphragm. It is an easy and common issue.

 

[Gertis]

Re: Sport jet 90 low power

Hi !

Im also new in this forum, My name is Gert-Ove Sundman and come from sweden, so i apologize now for language and writing.( sometimes it?s difficult to understand )
I have a Baja Blast with sportjet 90 hp. I?ve just got it and ride it twice. The first time it passes 36 mph ( alone ) and approx 8 gal.( 1 gal = 3,8 Liters ) for 40 min of riding. The previous owner said 40-45 mph.
The impeller is restored and riding plate correceted, this was important he told me.

Second raid today , We were 3 in the boat and top speed around 29-30 mph
I have of course some question for my own , and i hope i can give some answers back in a while.
1. Is this normal performance?
2. How bad can the riding plate be? , ( i can see it is a bit dented )
3. The boat "moves" a little bit in spite of neutral position, normal ?
4. It?s hard to start , when it?s warm and it seem?s hard to idle, for periods ?

Thank?s for help, it seem?s this forum must be the way to get in contact with the right people.

// Gertis

 

[Juster89]

Re: Sport jet 90 low power

ok sorry its ben a few days but here is my results of a trigger test.
and going be the 1100-1400 ohms rule i have found on here
i unplugged all 4 wires. i left the black meter leed in the whit/black wire.
took the red leed to each other wire. my meter only has auto ohms setting so here is the results

all white wire - .956 k ohms
purple wire- 1.293 k ohms
brown wire- 8.47 M ohms

i thought that the results where very different. but i tested each wire 4 times with the same results on each wire.
is my trigger bad. thanks

 

[e-spin]

Re: Sport jet 90 low power

Yes,

My manual states that the trigger resistance should be between 1100-1400 ohms at each connection. You have two that are close and one that is wacked out. This is very similar to what I remember my readings as, and replacing the defective trigger put me back on plane.

Let us know when you get it working!

E-spin

 

[Juster89]

Re: Sport jet 90 low power

i went to the boat shop today to get some parts i ordered for another boat. but i was talking to the mechanic and he said that more than likey my problem is my stator. i told him the readings of my trigger test. he told me that u cant really test the trigger and that the results will always very. im not one to argue so i did not argue with him. he said that my motor is a outboard motor that they stuck in a box and is gets sweaty in there and makes the stators bad. it might just be me but i think this mechanic is mostly full of crap.