94 Merc 4.3L v6 cranking issues

larr630

Cadet
Joined
May 5, 2012
Messages
19
Hi to all! Hope you are having a wonderful holidays!

I have a 94 Merc 4.3L v6. Went to start it after it had been sitting for 3 weeks. I sprayed a ton of carb cleaner down throat of carb to clean gummy stuff out and let it be. I went back a week or two later to start the boat and after half a crank, it would lock up and the starter made a grinding noise. I removed all the spark plugs and when I removed plug for cylinder #3, a bunch of liquid came out. There is no sign of water in the oil. I am wondering if this was the carb spray that funneled its way down into that cylinder and basically caused hydrolock? I attempted to do a compression test on each cylinder, but everytime I put any kind of load on that cylinder, the motor won't turn or compress that cylinder. Any ideas? I want to pull the head to see if i can tell whats going on, but would rather pull the motor and rebuild it during the winter. Just thought maybe someone had this happen and can give me a heads up. Any ideas on a repower also? Any ideas on what could be wrong? Any advise would help. Have a great holiday!
Larry
 

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: 94 Merc 4.3L v6 cranking issues

Will the engine crank over with all the spark plugs removed?
 

tpenfield

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Jul 18, 2011
Messages
17,621
Re: 94 Merc 4.3L v6 cranking issues

Hi to all! Hope you are having a wonderful holidays!

I have a 94 Merc 4.3L v6. Went to start it after it had been sitting for 3 weeks. I sprayed a ton of carb cleaner down throat of carb to clean gummy stuff out and let it be. I went back a week or two later to start the boat and after half a crank, it would lock up and the starter made a grinding noise. I removed all the spark plugs and when I removed plug for cylinder #3, a bunch of liquid came out. There is no sign of water in the oil. I am wondering if this was the carb spray that funneled its way down into that cylinder and basically caused hydrolock? I attempted to do a compression test on each cylinder, but everytime I put any kind of load on that cylinder, the motor won't turn or compress that cylinder.

Any ideas?


I want to pull the head to see if i can tell whats going on, but would rather pull the motor and rebuild it during the winter. Just thought maybe someone had this happen and can give me a heads up. Any ideas on a repower also? Any ideas on what could be wrong? Any advise would help. Have a great holiday!
Larry

Hello Larry,

Help us out a little bit . . .

An engine sitting for 3 weeks is no big deal . . . was there a reason for dumping carb cleaner into the intake?

Like Don asked . . . did you 'free spin' the engine with all of the plugs out? You should . . . that way you will know for sure if you got all of the carb cleaner out of the intake and thru the engine. Otherwise it will continue to hydrolock.

My idea is . . . don't do that again . . . in addition to trying the spin the engine with no spark plug in it. I would not consider taking the engine apart or anything like that at this point . . .
 

larr630

Cadet
Joined
May 5, 2012
Messages
19
Re: 94 Merc 4.3L v6 cranking issues

Hi guys. Yes I free spun the engine. By hand and by the starter once all the plugs were out. I sprayed the carb cleaner into the throat of the carb to try and clean the gum residue out of it. I put a new carb on it in April of 2012. My boat has an aluminum tank in it and the excessive heat this summer just destroyed the carb with its e85 stuff and the anti-e85 I use in the gas tank. I am going to change my tank this winter. When I initially tried to crank the boat up before heading out on the elephant ears, it just kept stopping at a certain point and the starter would start grinding. I pulled the motor in July and changed the flywheel which was worn out and I replaced that starter, so I thought that grinding was not warranted. Anyway, I grabbed my breaker bar and a socket and tried freehanding the motor after the grinding. Motor wouldn't move past a certain point. It would rotate backwards, but always stopped at a certain upstroke for that problem cylinder. So I decided to pull the plugs- all of them. The cylinder in question dumped liquid out of it when I removed the plug. So I realized that I had hydrolock on the that one cylinder. After removing all the plugs, I used the starter to rotate the motor to get rid of all remaining liquids. Then I started at cylinder #1 and started doing compression checks. Everything was going fine until I hit the problem cylinder. With the compression tester installed in the spark plug hole, the motor started the sammee thing. Would not move past a certain point and the starter started grinding again. I havent messed with it since. Thought I would get some ideas before attacking it again. I hope this info helps. Thanks guys for your time.
 
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