Motor shut off and smoking

[maxum_man]

Ok...I just replaced my Regulator/Rectifier, and I went today for the test run. While my wife was parking the truck the motor was idling. It just shut off like someone turned off the key. I raised the "hood" and looked and didnt see anything. So I cranked on the motor again for about 5 seconds. It hit once and didnt start back. I looked back at the motor and there was smoke coming from behind the mounting plate for the switch box. This is a 1992 Force 120 L Drive motor. I pulled the boat back on the trailer with a rope and got home to find that there is some sort of vacuum block? on the side of the motor that was cracked and gas/oil mix leaking from it while cranking. That was where my smoke came from. Had a local "mechanic" tell me I had spun a bearing, but I don't think I did because the motor is way too easy to turn over by hand with all plugs out. I took the "inspection" covers off the side and looked at #1,2,3 pistons and cant see any damage. Looks good inside from there. Should I pull the head off and check to see if a piston is burnt?
The "mechanic" told me that my problem of not going past 3000 rpm's came from a burnt piston that couldnt pull in enough fuel/air to one or more cylinders. Feasible?...I'm not sure. I say "mechanic" because this is the same guy that screwed a friend of mine on some carburator work.
What's it sound like to you guys!?

 

[roscoe]

Re: Motor shut off and smoking

to find that there is some sort of vacuum block?


??

Fuel pump maybe? That would explain the gas and oil.

It is operated by vacuum pulses from the powerhead.



You can inspect the pistons and cylinders if you want, but that will just add to the number of gaskets you need to replace.

Got a picture of this vacuum block?

And stay away from that "mechanic", you already know you can't trust him.

 

[maxum_man]

Re: Motor shut off and smoking

yeah...the vacuum block i am referring to is just a cover on the powerhead that has a few holes on the inside and a block with two hookups for vacuum lines. I will post a picture of it later (I'm at work for 24 hours).

This "mechanic" told me that I had a 75 or 90 hp motor because it was a 4 cylinder. he said that the only 120 hp motors were 6 cylinders and that 75-90 hp were 3 cylinders. So...I'm going to a different guy!!

But I will post a pic of that block later tonight. It is bolted to the block behind the mounting plate for the switchbox, if that helps any.

Bryan

PS-I just rebuilt the fuel pump, and I'm pretty sure its still okay.

 

[maxum_man]

Re: Motor shut off and smoking

I just found a picture on boats.net. It is called a cylinder drain cover. It has cracked at the top somehow.

 

[pnwboat]

Re: Motor shut off and smoking

The drain covers are kind of hard to find. You probably have to get a used one or look at some of the auction sites. Sent you a PM. Not sure if that would be preventing the motor from starting though.

 

[maxum_man]

Re: Motor shut off and smoking

Thanks! Any ideas what would cause that thing to crack at the top? Shouldn't be that much pressure in the crankcase huh!?

 

[pnwboat]

Re: Motor shut off and smoking

Cover was most likely cracked by over tightening. I doubt that internal engine pressure would be able to crack the drain cover.

 

[maxum_man]

Re: Motor shut off and smoking

Thats what I thought too! I was just wondering if something gave way inside and cracked it though. I pulled the plugs out and turned it by hand and it spins smoothly, I can't feel any bearings grinding against the crank or rods. If that is leaking from being cracked, do you think that contributed to my problem of not being able to run up past 3500 rpm's?

 

[pnwboat]

Re: Motor shut off and smoking

Can't say for sure if it was causing your problem. Regardless, it needs to be fixed, as the cylinder drain passages go into the by-pass passages where the fuel mixture flows to the cylinders.

 

[maxum_man]

Re: Motor shut off and smoking

Found both plates in Indy. Got em coming for $20!! I'm going to put them on when they get here and run a compression check again to see if I burnt a piston or lost some rings! I'll post results!

 

[maxum_man]

Re: Motor shut off and smoking

ok...I put the cover back on and replaced my trigger while I was in there. I checked the timing and it was WAAAAAYYYY advanced! So I set that and fired her up. Purred like a kitten in the driveway on the muffs. I'm going to the lake in a few minutes to test run it! I hope it does well!!