Logo
FULL SITE MENU

please help 1997 40hp 4cylinder 2stroke 2 cylinders not working

M

milocal17

New member
Bought a boat from a co-worker yesterday for much less than book value. The co-worker told me there was some engine problems therefore he would let it go for cheap. I pulled the carbs and put kits on them. New plugs and fuel filter because the motor had been sitting for over 2 years. I pulled it 3 times and the motor fired up, however it is only running on the bottom 2 cylinders. I looked at the old plugs and it looks like it was run like this for a while. The cylinders are getting both gas and fire but are not working. I am desperate to get out on the water. I have solicited advice from my dad who was a OMC dealer/mechanic for years and he seems to think it may be the reeds or worse. Is there anyone else that can help me out with this? Any tips would be greatly appreciated.
 
Not likely that reeds would fail on 2 cylinders at the same time.----------What happens when you squirt some mixed fuel into the upper carburetor ?--------Does spark jump a gap of 3/8 " on both ?-------You need to confirm that wires from switch box are hooked to the correct coils. Plug wires going to the correct cylinder?
 
Confused here - you are certain that the "two not firing" are getting "gas and fire"?

On this model if two cylinders are not firing it is almost always a bad trigger. Cylinders 1/2 share a trigger bobbin, and 3/4 the other bobbin.

But if you have a strong, solid spark at 1 and 2 it can not be the trigger.
 
If its a CDM ignition motor you have a bad CDM module as one can effect up to 2 others because they are in a series. Unplug them one by one and check spark, the one you unplug and spark returns is usually the bad one. Also CDM triggers dont fail to often... If you have a ADI motor with switchbox it likely a bad switchbox . It could be a trigger but a quick test would be to swap the trigger leads on switchbox. The switchbox fires from bottom up so #1 is lowest coil wire and #4 is top coil wire, just remove the wht and violet wires and move brn and wht/blk wires to those terminals. If fire returns bad trigger if not bad switch box. If you check all 4 for spark before testing and they are all firing the top carb has a problem or engine has compression problem
 
Last edited:
Back
Top