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Conference vicki::boats

Title:Powerboats
Notice:Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:KWLITY::SUTER
Created:Thu May 12 1988
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1275
Total number of notes:18109

1179.0. "OMC 4.3l Won't accelerate" by SALEM::FLYNN () Wed Aug 03 1994 14:45

    
    	Hi,
    
    	Sunday we took our Four Winns 20 ft'er out for some tubing. We
    	had 4 adults and 4 children on the boat. While trying to 
    	accelerate to over 30 mph, I noticed that the boat started to 
    	accelerate as usual and then I felt a dip in power as I
    	moved the throttle forward. The boat wouldn't go over approx
    	18 mph from then on. I had to drive another 20 minutes or so and
    	I didn't really feel or hear any strange behavior from the 
    	engine. It's a 4.3L OMC Cobra six. My wife complained that she
    	smelled an unusally strong odor of gasoline as we were driving
    	in. I have an appointment tomorrow with a repair shop but I've
    	died many deaths since Sunday wondering how serious this might be.
    
    	I know this isn't much information but can some of you "technically
    	gifted" boat owners either allay my fears or bury me once in for all
    	with some possible scenarios (good or bad) good preferred of
        course. I can't wait until tomorrow and I need to feel better!
    
    	Bob
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1179.1The good, the bad and the ugly...NITMOI::WOODWed Aug 03 1994 15:1528
    Good scenario??? With a boat problem ?$? ;-) 
    
    Seriously though, I've had the same problem before and it turned out
    that the points were bad. Cheap fix on the water is a file, and maybe
    20 dollars for a set once your at home. I'm not sure what a shop will
    charge though. Bad news could be something like a seal blew in your
    outdrive, all the oil came out and the gears got so eaten up
    and scored that the boat doeasn't have enough power to turn them to
    full throttle anymore. They will seize totally at some point soon.
    Cost for a rebuild should run from 2-3K. :-) I've seen this one too!
    Here's another one. The motor is overheating to the point that the
    pistons expand and start to constrict. Massive failure is moments away
    if you didn't stop when you did (your temp sensor is broken and the
    smell your wife noticed is the hoses starting to melt on the block, not
    gas). You may be able to fix the broken thermostat now, but you just
    took 1000 hours off the life of the engine :-)
    
    How about one last minor one. The belts are slipping on the water pump,
    and belt dust has gathered on the air cleaner assembly. The motor is
    starving for air, and not using all the gas being pumped into, hence
    the smell. I've been bitten by all of these with my 4.3 OMC before!
    Plus a few more problems....I vote for the points or the belt dust...
    
    Good luck,
    Marty (who picked up the boat saturday from having a broken engine
    coupler replaced, and it overheated within the first mile and is
    back in the shop once again)...
    
1179.2SALEM::FLYNNWed Aug 03 1994 15:2312
    
    	Thanks for the quick response Marty. I did look constantly at the
    	temp guage and it didn't go over 160 degrees. I stopped at one
        point and the temp went up gradually and peaked at 160.
    
    	Did you mean the oil in the lower unit? The oil pressure for	
    	the engine was right up there all the time. 
    
    	Hope you're right about the easy stuff!
    
    	Bob
    	
1179.3Another possibility...RENEWL::URBANWed Aug 03 1994 16:5015
YOu might see that behavior if you have a fuel filter(s) becoming clogged.  It
will be fine at slower speeds but cannot pass enough fuel at higher speeds.

One way to check this is to throttle back to idle for a while then accellerate;
if it runs up and then after a short while drops off again filters are
the place I'd look first. 

Then,

The other possibility may be a ruptured fuel pump diaphram.  That will limit
the fuel to the carb and usually pumps fuel out thru the clear tube and dumps
it in the carb, causing a 'flooding' condition.  THis might account for the gas 
smell your wife sensed.

Tom
1179.4Loose nut behind the steering wheelSALEM::FLYNNThu Aug 04 1994 10:0519
    
    	An update....
    
    	I dropped the boat off this am and after telling me about the
    	"blown piston problem" that many OMC Cobra's have had, I started
    	to wonder if this guy was gonna ram me regardless of the problem.
    	I hadn't even picked up my "lamb suit" from the cleaners yet! Rats!	
    	
    	Anyways, he decides to lift the engine cover off to see if there	
        were any obvious problems. He started rummaging around and he looks
    	at me and smiles, then a little chuckle, panic sets in....he says
    	"I found one of the problems if not "THE" problem", one of your spark 
    	plug wires was disconnected." Relief tempered with cautious optimism 
    	spreads across my face. My faith in this guy has been restored. He 	
    	said he would pull all of the plugs, change the fuel filter, and
    	what not but he was pretty sure that was the problem. I think have
        may have dodged my first boat tragedy bullet. Thanks for the help!
    
    	Bob 
1179.5good newsNITMOI::WOODThu Aug 04 1994 11:324
    Any more details on the blown piston problem many cobras have had?
    That's a new one to me...ouch...Glad your problem was just a plug
    wire, although i can't see how it would ever have gotten up to speed
    even briefly???
1179.6SALEM::FLYNNThu Aug 04 1994 11:487
    
    	I'll check with him for more details. It was the first I had
    	heard about it too. Man I'm sure glad it isn't that. The guy
    	seems to have alot of experience and he said it would be many
    	$ to fix. I'm a bit surprised that a large recurring problem
    	with the OMC 4.3 would not have been exposed here. It seems like
    	a lot of boaters in this file have a lot of experience with them.
1179.7SALEM::FLYNNFri Aug 05 1994 10:119
    
    	Final resolution.....plug wire off. Ran the boat last night.
    	Ran like a Swiss watch. 
    
    	Back in business...
    
    	Thanks for the help.
    
    	Bob