97 Speedster Starboard Motor won't run

[nitrotate]

Hi guys need a little help here. Been searching but can't seem to find any posts close enough to this:

My port motor runs great. Starboard just stopped running suddenly yesterday. Won't start in water but will start and idles rough out of water but dies when I move the throttle.

• Rebuilt both motors at the beginning of last season, cleaned carbs really well and set pop off correctly
• Boat ran flawlessly all summer last summer
• Winterized it properly by fogging carbs and cylinders
• De-winterized two weeks ago
• Installed brand new marine battery
• Ran great for the past two days on the lake
• Compression is 145psi in both cylinders
• Verified I am getting spark
  • only weird thing is I only get spark to the wire I'm testing if the other is connected to the plug while installed in the motor
• Carb is getting fuel (new fuel)
• New BR8ES plugs (old plugs were nice cardboard brown when it quit running and not fouled)
• No blown fuses in the MPEM
• Accelerator pump is spraying fuel when I move the throttle
• I don't think it's a carb issue because I've swapped over the carb from the running motor and the problem persists
  • Just to double verify tomorrow I'm going to put the carb from the non-running motor onto the running motor and confirm
• Tomorrow I will also double check to make sure fuel is flowing through the lines from the tank

The only thing I can think of now is either some kind of electrical issue I'm not seeing, or some kind of rotary valve issue??

Anyone have any pointers?

 

[etemplet]

Buy this from Auto Zone or Amazon. You may have a weak coil. These will let you know without a doubt if you are getting spark and you can tell if it is weak or strong. I love em' Good Luck !!

 

[nitrotate]

Yep I have one, that's how I tested. Didn't seem weak but I'll test the other motor and compare.

 

[etemplet]

I had a XP that wouldn't start as long as I held the start button engaged. As soon as I let go of the start button the ski would be running. After dark one night I was still troubleshooting the ski and the skeeters were tearing my azz up, I had those testers hooked up. I had checked battery voltage drop and all sorts of stuff and I was determined to find the problem. As I engaged the starter I noticed the testers brighten up when I released the start button and the engine, of course, fired right off. I know it sounds strange but in releasing the start button the engine is still spinning a bit and that is the point at which the engine would start... every time. That would have been a shot in the dark guess but with those testers connected I suspected the coil was weak and the voltage draw from the starter spinning just wouldn't give it the UMPH it needed. Sure enough, the coil was the problem. That's why I love these testers. Good Luck !!

 

[nitrotate]

Ok so I tested the other side and both engines light up the tester about the same brightness. The starboard motor will start and idle but I can't get it to run up over 1500 to 2K RPM (and yes I've tried it with the drive selector in neutral and forward).

 

[etemplet]

You can try swapping the engine wires from the MPEM and see if the same thing happens with the good engine. I hope it is not your issue but the rev limiters on the MPEMs seem to be a problem at times. I do have a Spare MPEM complete and It will be about 1/2 the price people sell them for on the internet. Good Luck !!

Did you check the plug going into the Mag? Sometimes those connections break down. That is what was wrong with mine when I bought the extra MPEM. Good Luck again !!

 

[nitrotate]

You can try swapping the engine wires from the MPEM and see if the same thing happens with the good engine. I hope it is not your issue but the rev limiters on the MPEMs seem to be a problem at times. I do have a Spare MPEM complete and It will be about 1/2 the price people sell them for on the internet. Good Luck !!

Did you check the plug going into the Mag? Sometimes those connections break down. That is what was wrong with mine when I bought the extra MPEM. Good Luck again !!

Let me try that. I assume you mean swap over the coil/wires between engines right. I don't think I can just "use" the left side over on the right can I??

 

[nitrotate]

I swapped the MPEM-to-coil wire from the starboard (bad motor) coil over to the port (good motor) coil then used those plug wires on the starboard motor. Got the same results so I assume both coils are good... I know this doesn't necessarily eliminate the MPEM rev limiter possibility but does the MPEM rev limit the motors independently of one another?

 

[nitrotate]

Ok new update but still stumped on this issue... I swapped the carbs and the good motor runs perfect with both carbs so the carburetor is ruled out. I'm getting fuel flow to the bad motor so that's ruled out. I just ordered two new ignition coils just to see if that does the trick but the spark strength seems the same across both coils at the moment.

Not sure how to test the stator/magneto yet... seems like I need a special test harness??

 

[nitrotate]

Update; I had to leave town for a couple weeks but before leaving I tried the following;

1. Magneto/stator tested out good (checked both motors, similar results)
2. Coils and caps all tested good
3. Swapped carbs and good motor still runs with the other carb so carbs are ruled out
4. Swapped engine wires from MPEM to see if rev limiter on the bad side was the issue and the good motor ran fine so MPEM seems ok

SO, the only remaining possibilities I can think of now is the rotary valve and/or shaft and possibly timing but I'll check the rotary first. Hoping I can get the rotary valve cover, plate and shaft out without removing the motor... I'll give that a shot when I get back home.