90 Sport Jet Carb float question

Redbarron%%

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I have cleaned and set up the three carbs on my Sport Jet 90 and when I bought it it had plastic floats in the carbs that have no way I can see to adjust the level.
They are all a little too low (or too high when held upside down).
The plastic floats have plastic tangs that as far as I can see and try if bent just pop right back where they were.
All three are the same.I read an article where a guy has problems getting full power with these and he put his old metal floats back in.
I was having problems getting 5100 rpm in the boat, but a redo of the ignition took care of this, but I have a slight miss at full power.
By the way I updated the ignition with CDM modules off a late model 200 hp Mercury and a 50 HP three cylinder harness and dropped the switch box and adapter etc in the storage bin.
The Motor had the red stator coil so that was compatible. I also had to change the trigger as one cylinder was not getting a pulse and the resistance test was off.
Now who knows about the floats?
 

racerone

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Some will argue.-----Many folks pick on the carburetors for some reason..-----But what are the results of a compression test.
 

pnwboat

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All of the stators that I've seen on the CDM ignition systems have the White/Green and Green/White stator wires. From what I can see in the parts manuals, the stator for the Switch Box ignition system has a different part number and resistance readings from the stator used for the CDM ignition systems. Both of them are red. I don't know if they are interchangeable.

Also the CDM ignition system uses a special trigger that uses electronic Hall Effect transistors to fire the CDM's. You cannot check the trigger using the Resistance Function on a meter like the older triggers.

If you are checking the trigger that you are currently using and getting resistance readings, then you have the wrong trigger. It may work, but probably not well.
 

jerryjerry05

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The white floats are a JOKE!!
I don't know who designed them but they are one of the worst things they try to sell.

If you can find the old style?? put them back in.

Slight miss at full throttle. Maybe the reeds?
Any fuel coming back out the front of the carb?

They made the sport jet with a bunch of different carbs and electronics.
It helps if you post a year and model???
 

Redbarron%%

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My engine seems to be somewhat of a Frankenstein in that it is new enough to have the square Mercury fuel pump but not the oil injection pump.
I believe it is a hybrid put together with the Sport Jet crank so that it will fit the jet.
There is no spitting from the carbs and I have pulled the reeds and they and everything else looks new.
I would put the old style in if I could find some, but so far I have seen none for sale yet.
I wonder why they would have basically nonadjustable floats, but there we are.
The needles I have are the rubber tipped ones. The bottom carb was just a little sticky and did not fall free when turned right side up and I ordered a new one and it came in as a solid stainless needle.
I have not installed it yet.
The ignition has the red stator, 200 HP late model CDM and late 50 hp Mercury wiring for the ignition.
The trigger works OK as long as you match the proper Trigger with the proper flywheel whether it is Hall effect or magnetic.
Personally I think the best place for the switchbox, adapter, and old style coils is where I have them now, the bottom drawer of my tool box.
By the way the Red Stator has the white/ green and green/white wires and connect to the harness from the 50 Merc.
The colors of the wires from the trigger to the CDM happen to be different so I matched them up with the timing light.
The engine seems to run a little differently after I replaced the base gasket and sealed up the leaks there and reworked the grounding of basically everything.
As soon as I get a change to put it in the water to test I will get back to you guys.
Thanks.
BTW if you know where I can get a set of old style floats let me know
 

pnwboat

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The CDM ignition system seems to be very reliable and easy to trouble-shoot.

I found a set of the plastic floats with the metal tabs a few years ago. The carbs they were in had been damaged, but the floats themselves were fine, so they were cheap. Been using them for the past 6 or 7 years. They're not that common but do show up from time to time.

Any vacuum leaks around the carbs or intake area will affect the motor. Hopefully that's all it was. Your ignition system seems to be in order. The grounds are very important too. There is a service bulletin regarding adding an addition ground wire between the CDM mounting plate and the engine block.

Good luck! let us know how it goes.
 

jerryjerry05

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Some sport jets didn't have oil injection. They were a combo of Force and Mercury parts.
The solid needle will leak unless you have the rubber in the seat.
Do the starter fluid spray at the intake side and see if it makes a difference.
The place the FP sets is called a port cover.
It can leak/suck air and cause problems.
ONE!!! little backfire or even a cough can blow the port cover gaskets.
 

Redbarron%%

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Thanks for the info.
I have added several ground wires tying various parts together and grounding to the point where the battery cable is located as well.
As to the trigger I think that the CDMs will fire with a trigger pulse over 4 volts and checking that that brought me to recheck the trigger coils. I had checked them earlier, but one was bad.
The new one is correct on all three circuits and I think that it is OK now.
The red stator was designed to work with the CDMs and to work with the old switchbox required the adapter to output the correct voltage.
Personally I think that the new mercury system is simpler and easier to troubleshoot and more reliable than the old system.
If anyone wants some old parts give me a PM.
I am taking to boat out today to check it out and see if the very slight WOT miss is still there. It does pull rated RPM at WOT for the jet so there can;t be a lot wrong with the system.
With the bad ignition it would only turn 4200 or so and the bottom plug was obviously not working.
It would fire at low rpm a little.
I found the problem tire up at the dock at power checking for a spark with the timing light.
This engine has been a real bear toget right.
First was a problem with water getting in the cylinders, finding finally that the base adapter gasket was incorrect and torn getting into the exhaust outlet from the water inlet for the outboard. Plugging the old water inlet with JB weld stopped the leaking and finally having to fix the leaking at the base by pulling the head and replacing the gasket.
Add the ignition problems that are pretty common with the Force and it's reputation.
Personally I think I would bite the bullet and upgrade to the red stator, CDMs and late model compatible harness and lose the old complications.
Carbs are simple as dirt and need to be clean and adjustable floats would help too.
 

Redbarron%%

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Success with running the boat today!
There is a little surging even after I changed the plugs. The "miss" seems to actually be an increase in the RPM a little and not a decrease.
Since I have not fine tuned the mixture and left them at 1 1/2 out there is something to be gained there.
The mixture might be a little rich in the mid-range.
The engine is pilling about 5000 rpm and that is within tolerance, if the tech is right.
The surge doesn't really show um on the tach, but more of a "feeling" at this point.
 

jerryjerry05

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The "mix" is for idle only.
It shouldn't affect it once you go past idle.

The main jet controls the mix after the idle.

One way to test: run the motor and get it up to operating temp( make sure the thermostat is still in the system) run it at wide open for 4-5 min.
Then turn the key off. Don't throttle down just turn the key off.
Then pull the plugs and check the condition of the burn.

Load in the boat can affect the rpm's.
 

Redbarron%%

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I agree to some point on the idle mixture and screws, but on the Force there are three ports fed from the idle circuit and the carb throttle plates actually open very little while the timing is advanced until you get to the very last part of the total movement of the tower arm due the the shape of the actuating cam.
I haven't looked inside the carb vs the holes and plate and throttle percentage but the actuation of the actual plates is very non linear.
I assume that this is for "economy" and at WOT the timing actually is reduced to 30 * from quite a bit more at more or less mid throttle.
I test ran the boat for several hours the other day and the speed achieved i thought was 32 mph when the rating in 1995 was 38 as my boat is equipped so I thought I might be down on power.
I looked at the phone app yesterday and saw the speed was logged as 32 Knots or 36 mph, much closer than before.
 

jerryjerry05

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The speedo's on the boat aren't always the most dependable.

Is the throttle opening all the way?
Have someone drive and you manually open the throttle?
 

Redbarron%%

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It took a long time to get the low timing 8*.max WOT timing at 30* and the throttles 100% (horizontal), but they are 100%.
The speed I have is GPS and the Boat test???
Every things seems to be OK, enough so that I bought a Garmin EchoMap 74 SV on sale at West Marine.
Just a little fine tuning and getting everything just right.
A couple of MPH doesn't really make that much difference to me for a flats Skiff, but being right and reliable does.
 

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jerryjerry05

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At wide open, the throttle plate doesn't need to be level.
Try opening the throttle while underway.
 

Redbarron%%

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Yes the plate is level and the throttle lever works correctly or at least the mark on the lever is parallel with the carb ans looking in the throat that is correct.
It took a lot of work to get the timing and the throttle position correct at the same time.
The RPM is in the proper range for WOT at ~5000 5100 rpm for the Sport Jet.
A few MPH won't make a lot of difference.

I suspect that what I call FrankenGrate may be making the few MPH difference vs the stock inlet.
It is actually only a few mph and I can live with that, if the engine is operating correctly.
 
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