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1990 Merc 40 won't start

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matthewharrison

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Okay, theres a bit of a story behind this so bare with me. As the title says, I have a 1990 Merc 40, 4 cylinder 2 stroke. I just recently finished rebuilding the motor, in the process of rebuilding I took out the driving gear for the oil injection & now mix it 50:1. After finishing the rebuild I got it to run but had trouble keeping it running, found the cork gasket in the float bowl of one carb was torn, so I made my own out of an o-ring to get me by while I waited for my carb kit to come. Got it to run but it would spit & sputter every now & again, found out that problem was a broken magnet on one of the ignition coils, swapped for a new coil & it finally ran good. This was all done on muffs in the driveway.

We finally towed it down to the wharf and launched the boat. Had a hard time getting it to start & stay running at first, finally got it running and started out into the water. While we were going I had the throttle wide open in forward but it definitely was not getting up to the RPM it should, in neutral it would rev up fine, but once in forward it wouldn't come near the same. After about 5-10 minutes the motor started stalling every now & again. The stalling started getting more frequent to the point where we could only get it to run for a few seconds before it would stall again. We ended up getting towed back in. I figured the majority of this was all related to the carb & the carb kits I ordered would solve those issues.

After getting the boat back home I decided to try it on the muffs again to see if it would make any difference, but it didn't. The motor would start for a few seconds then die out. It was dark out so I gave up on it for that night. The next day I went out & tried it again, I noticed fuel leaking out a bunch so decided I needed the carb kit before going any further.

Today I got my carb kits, new gaskets in both carbs, put them back together & back on the boat. Hooked it up to the muffs & couldn't get a kick out of it. After trying it some more it finally kicked but didn't stay running. I'm still seeing fuel dripping, it's dripping off the bottom part of the throttle lever on both carbs. I can't tell if it's run off from somewhere else or if it's leaking out lower throttle lever part that connects the 2 carbs. I did notice fuel coming out the front of the carb throat too. Is it flooding itself?

Not sure where to go from here, so if anyone has some ideas feel free to throw them at me.
 
Well, I just had a sad realization....while we were out on the water when the boat started to die we figured it was running out of fuel because there wasn't much in the tank, but I had grab a jug from my parents earlier & brought it aboard the boat. After we added fuel problems really started. It just clicked in my head, my father owns a bull dozer & I now think that the fuel we added was diesel. In my rush to get the boat in the water I never even thought of that or thought to check the fuel. What should I do if this is the case?
 
IF you had it running under load with the diesel in there, you might have drilled a few pistons. Since it barely ran, and at idle, it should be okay. Clean all that crap out of there and put in fresh GASOLINE.

Jeff
 
Gotta tell you a non-boating tale: My brother was cruising out in the country one night with his large chested girl friend when his Hudson Hornet started running low on gas. Desperate, he added a gallon of diesel fuel that he had with him, and the old gal (the car) made it back home. She was unhappy--pinging like crazy and shaking a bit--but was still running.

Jeff
 
Hah, good story. Now I found out my power issues, cylinder 3 & 4 aren't firing. I swapped plugs, swapped coil packs, no luck. Tried an ohm meter on the trigger wires, didn't get any readings, so now what?
 
I seen online to try swapping stator wires, red/white with blue/white and solid red with solid blue, I did that and it wouldn't even kick, swapped them back & it started again.
 
My grandfather has a 1980's Yamaha enduro 40, wonder if anyone knows if there's any chance of the stator off that working on mine, I do want to get the proper one but it's the summer festival here in my town & it would be nice to take the boat out tomorrow if it was possible.
 
Well, I'm curious as to why the stator would do this.

Today I checked output voltage on the wires, one high speed had correct voltage & one low speed did as well. I disconnected the wires with no output & checked them, they now had correct voltage & the ones that were working before & are still connected have none. I decided to test a little further. I disconnected the wires that were originally working & connected the ones that were not originally working, upon doing this the disconnected ones once again have proper voltage & the connected one have none. If I disconnect all 4 it goes back to just one high speed & one low speed wire with proper voltage.

Seems obvious I need a new stator, but what would make it act that way? I can achieve proper voltage in either set of high & low speed wires by disconnecting them while having the other set connected, but with all 4 connected or disconnect only one set of high & low speed wires is working.
 
Tried even more, just found that the voltage is only going to the bottom high & low speed terminals. If I swap wires it's the same thing, voltage only goes to the bottom two. This seems strange to me, could this mean my switch box is bad? Should voltage still come out of the wires even if switchbox is bad? Both sets of high/low work on bottom terminals, neither will work on top two. With one high & low speed wire working should I get fire on at least 2 cylinders?

EDIT: Tested the trigger, no resistance between #3&4, #1&2 have proper readings. Seems I have a faulty trigger as well. Which terminals on the stator side supply power to cylinder 1 & 2? If it is the top ones then that would explain no fire. If not then my problems must go further.
 
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