Sport Jet 90 Will not plane and has no speed, HELP!

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Ive been reading your tread and im having a similiar issue

- all plugs fire and idle
- carbs are spotless
- engine runs and idles great

so when i take off I give the boat WOT and the rpm guage goes to 6000 for like two seconds and then backs down to 4500rpm and wont go any higher IF i lean forward enuff it will eventually plane off but only do 19 to 20 knots

I tried the pulling off the sparkpug wires of while trying to plane off and 1 and 3 made a difference ( engine bogged ) while 2 did not. I was able to plane off with 1 and 3 and leaving off the 2nd cylinder plug wire off.

I swaped the coil pack and spark plug from 1 to 2 and still leaving off the plug wire of the second cylinder did not effect the motor at all still topped out 20 kontswouldnt rev ofer 4500 rpm

what finally fixed your problem jsut swaping around the coil packs around???

the motor is a 1996 95xr sport jet, the hull is a 15ft hobie jet

Do you have the CDM model?. Don?t run it without a good grounded spark plug in hig power lead. It can kill the CDM module. Better is to plug out the wire connector coming in to the CDM.


Disconnect the rev limiter and test.

If you put a spark plug in that line and ground it good. To the cylinder that falls out . Does it give good spark, no misses ?.

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

heres a lil more information ... it has good spark on all three cylinders and i did a compression test on all three cylinders roughly 150 on all 3 give or take a few ( 150 149 150 ) you cant get the metal cover off the top of the engine to check anything there the bolts seem to be stripped so ill hit them with the grinder when i get home, and get to the flywheel, and continue the investigation.

any one know if the reed valves will affect the compression ??? im assuming that if i have good compression then the reed valves are fine although. im not positive that i can correctly assume that or not. how do i tell if its the cdm model or not ??

Thanks

 

[Trailratethisfx4]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

from what it sounds like to me, its your rev limiter thats what i would be looking at.

 

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Does it run on all 3 when ideling?.

Disconect rew limiter and try.

Check the carb on the cyl. that not working. Check so thin venting line/hose left side ar clear. And clear in connection on carb too.

If reeds not working it normally does not run well on ideling ore are hard to start etc..


CDM model have plug-in connector from the electric lines (4) to the CDM coil .

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

at idle in the driveway it fires on all cylinders when you adjust the air fuel mixture on each carb the engine will bog Ive been tru the carbs and all the fuel and vent lines that part of the motor is spotless. I have replaced the diaphram and the check valves in the fuel pump Im getting good fuel to the carbs it will turn over mabey twice and then fire up when you hit the key. When its warmed up it will fire up on a half turn( all you got to do is bump the key). and she runs smooth and perdy Im going to find the rev limiter and disconect that thing and try it !! ill keep you all posted

 

[aksor]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Also check your trigger resistance and post results!

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

ok so its not the Revlimiter. i took it out yesterday and disconnected the revlimiter and still no change I got to get a manual so i knoe what im doing with this thing.

I also hapened to look and i my stator is red !! is that the good one to have or the bad one. I know thee were opinions that one was better then the other. but cant remember which one was suposedly better!!

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

my next step is to like aksor said, get the fly wheel off and inspect the stator and all that good stuff.

Just out of curiosity do any of you guys have a book for the 1996 95xr sport jet? It if so can you post what wires i should be be ohm ing out ? Ill get the fly wheel off and try to follow everything that way but i guess it would be better to know that im testing the right stuff as well

 

[aksor]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Hi

The white green and green white wires are the ignition capacitor charge coils these charge up the capacitor inside the cdi unit. they should be between 500 and 700 ohms,

The two yellow wires are the battery charging coils that go to the voltage rectifier/regulator and provide power to the battery/ auxiliary lights, bilge pump,blower, ect. they will be very close to a few ohms almost a short when measured.

The trigger wires have to be tested as follows white black to white, white black to brown, white black to purple and it should be between 800 and 1400 ohms they are usually at 1200 ohms.

If the trigger reads out of bounds time to replace.

 

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Red stator is the better one. You can test the most out without taking the flyweel of.


Looks on the Year and motor that you have the later ingnition system .


If not trigger.


Timing?.

Check negative ground from engine to CDM. It?s the black line in the 4 wire connection. Check between grounding screw in other end of harness and the connection to the CDM with a testing instrument. Check all 3 so there is totally connection.


Have you changed the spark plug on that cylinder and tested?.


Disconnect kill swtch cable and test yellow/black line . Should red 0-2(max) volt with ingnition of/on.



I had a CDM coil on mine that worked on low rpm and died on high rpm. So it can be a CDM unit also. They are tricky sometimes to se if ok. Even if you measure them ok.

 

[Pdillie25]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

my next step is to like aksor said, get the fly wheel off and inspect the stator and all that good stuff.

Just out of curiosity do any of you guys have a book for the 1996 95xr sport jet? It if so can you post what wires i should be be ohm ing out ? Ill get the fly wheel off and try to follow everything that way but i guess it would be better to know that im testing the right stuff as well

Hey there I know how frustrating these jet boats can be. I'm a certified merc tech and just had the same problem with one of these at the shop... Pull the carbs back off, Pull the plates behind the carbs there's reed cages, check them make sure there isn't any chips or missing paddles on them, they can have a little gap in them tolerance is .20 thousands... if there is replace them chipped reeds is caused by overload and missing or shattered paddles is caused by over revs.. Its worth a check good luck to ya

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

I have never felt with reed values before do you think the reed valves are a problem even if I'm getting 150 compression out of all three of the cylinders ????? I guess either way I should check it just to rule it out

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Red stator is the better one. You can test the mnost out without taking the flyweel of.


Looks on the Year and motor that you have the later ingnition system .


If not trigger.


Timing?.

Check negative ground from engine to CDM. It?s the black line in the 4 wire connection. Check between grounding screw in other end of harness and the connection to the CDM with a testing instrument. Check all 3 so there is totally connection.


Have you changed the spark plug on that cylinder and tested?.


Disconnect kill swtch cable and test yellow/black line . Should red 0-2(max) volt with ingnition of/on.



I had a CDM coil on mine that worked on low rpm and died on high rpm. So it can be a CDM unit also. They are tricky sometimes to se if ok. Even if you



i swaped measure them ok.[/QUOTE



I swaped the pack and the spark from cylinder 1 down to the second cylinder. and still the second cylinder was the problem child so the problem lies before the coil packs (im guessing)

 

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

Well if carb ok. You are shure nothing is clogging mainjet in carb, so it runs on low but not on high. Mine run like that in the beginning, it was a litte flake of debris, laying in house/fuel line inlet, just before needle valve, makeing it run on low rpm but shutted close on high rpm, acting as a valve. Didn?t see it before i unscrewed the fuel inlet ( that the fuel-hose is connected too on that carb).

You have changed spark plug on that cylinder , ore checked it ?. And you switched the high power lead too, From CDM to Spark plug?.


Check electric wire harness on engine, You can measure in the plug harness to the cylinder thats dead, and se so you have the volt from the trigger to that CDM.

You have ABCD in connector to CDM, C= from trigger , volt test it . Put positive on that line with plug in CDM and motor running ( just stick a needle or point in testing wire from volt meter in to the lead on C), negative on ground/motor, and then switch to A in contact ( then you see so earth is good on that CDM), see so you get the same reading .

From trigger shall be 2,0-8,0 volt. Over that check CDM, under that faulty trigger. Running on ideling.

Stator output test = D in contact / positive volt meter, then negative on A ore ground engine , shall be 200-350 running on ideling.





And just for checking.


What volt do you have on battery when motor running ( + - cable on battery)?. Just so Recitifer is ok.. You have like just under 12 ore around 12 with engine off , and over 12 up to 14-14,5 volt max with engine runnig.

 

[bkhitchens]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

I have posted in this thread earlier. I had the same issues. It turned out to be the stator.

Clean carbs yearly. Keep your grounds and electrical connections clean. If it doesn't run right, it is because of electrical problem or fuel starvation. If it idles and runs, but doesn't get on plane it is the stator, or in rare occasions the ride plate is bent or has come loose.

In one year of SJ ownership I have had blown head gasket, loose ride plate, bad kill box, bad switchbox, bad stator twice, bad ground, dirty carbs. I am sure I am forgetting something. All of these issues have killed a day on the water. I hate the boat except for days like yesterday when it was running great and the kids had a blast tubing and zipping around in the boat.

 

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

I have posted in this thread earlier. I had the same issues. It turned out to be the stator.

Clean carbs yearly. Keep your grounds and electrical connections clean. If it doesn't run right, it is because of electrical problem or fuel starvation. If it idles and runs, but doesn't get on plane it is the stator, or in rare occasions the ride plate is bent or has come loose.

In one year of SJ ownership I have had blown head gasket, loose ride plate, bad kill box, bad switchbox, bad stator twice, bad ground, dirty carbs. I am sure I am forgetting something. All of these issues have killed a day on the water. I hate the boat except for days like yesterday when it was running great and the kids had a blast tubing and zipping around in the boat.

Hahahaha

Yes, you come to a point you think the boat is poltergeisted.


Well after working on this engine for some month now i start to learn it. And i have never seen someting/engine that act like this. The conclusion is that if something that is bad ore so-so, it can kill another thing easy on this engine.

It?s too bad, becaurse it?s a okay boat and engine (shlurping gas like a elephant) when it works as it shall. I?m thinking on mounting of the 120XR engine and put on something else on top. A V-six ore some 4 that rev up to 7-8000. Ore a TD engine had been best for the wallet , but probably to low rpm.


We can start a therapy-helping group soon here. So we dont end up at KO-KO nest, all Merc. 90-120 owners


Regards from Sweden ( with the boat running for the moment )

 

[silverado82481]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

i will defenatly sign up for that theropy group. its just weird the way it runs seamingly perfect in the driveway and idles fine lol hopfully i can get out there and hava look this weekend and at least single out the problem. im getting lazy and jsut takeing out the 20 ft Grady White, instead *knocks on wood* shes runnig good. for now

 

[Pdillie25]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

I have never felt with reed values before do you think the reed valves are a problem even if I'm getting 150 compression out of all three of the cylinders ????? I guess either way I should check it just to rule it out

Yes reeds have nothing to do with compression or leakdown im almost certain your going to find something wrong with the reed cages

 

[aksor]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

True that I tested my compression with the reed cages removed and it did not alter my compression readings. Once the transfer ports are blocked by the piston air fuel gets compressed between the piston and cyl head. + the reed valves would not stand up to 150 psi pressures.

The only things can affect compression is holes in the piston broken or stuck rings, broken piston skirts, bad head gasket, cylinder damage.

 

[Anders67]

Re: Sport Jet 90 Will not plane and has no speed, HELP!

MMMMMM.

Well now i put in a electric fuel pump in mine too, pumping around 6 psi.

I will not change pistons again. :facepalm:


http://www.facebook.com/photo.php?f...55624085537.2146293.1109507357&type=1&theater


http://www.facebook.com/photo.php?f...55624085537.2146293.1109507357&type=1&theater


http://www.facebook.com/photo.php?f...55624085537.2146293.1109507357&type=1&theater


Well, now i know how this engine looks inside. Not fun engine to take apart. But pulled engine out, and back in boat in around 5 ours with piston swap and honing.
All bearings looked like new, so i don?t think it have been runned mutch. Probably been seated somwhere not working for years.



Another thing. Can someone tell me what NGK BZ7HS-10 is for special spark plug, and why NGK list it for this engine?. The only thing i founded out is that it has.

B= 14mm

Z= inductive resistor

7= Heat rating

H= 12,7 mm thread lenght

S= Standard

10 = Gap



Z= Inductive Resistor Type. What is that ??: .