'72 chrysler 70hp outboard failing at high speeds

J

jayprice7

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Joined
Jul 31, 2004
Messages
13
I recently purchased a '72 chrysler sport fury with a 70hp chrysler outboard motor. I finally got the thing running, but when I turn the throttle to a high enough speed to plane out, the engine cuts out completely. Any thoughts as to why this might be happening would be much appreciated.
 
eurolarva

eurolarva

Rear Admiral
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Jun 24, 2003
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4,182
Re: '72 chrysler 70hp outboard failing at high speeds

First off does the motor run all right at idle and at medium speeds. When you go to high throttle when the motor is getting ready to die have you tried choking the motor to see if it improves? If motor improves chances are the problem is fuel related. Try running it with gas cap on gas tank partially open. Your tank may not be venting correctly. You mentioned you finally got it started. Were there other problems? How long was it stored before you ran it? Chances are the motor was stored with old gas. The gas may have varnished or had water in it causeing problems with the carbs. If it only happens at high speed it could be that the floats in the carbs are sticking shut and the motor is not getting the fuel it needs at high rpm and killing. I would start with rebuilding the carbs. It would not hurt to replace the fuel lines and rebuilding the fuel pump. These are not complicated tasks. Get a manual for your motor. If you rebuild the carbs do one at a time and dont mix parts from different carbs. This problem is common on motors that arent put into storage or winterized correctly. Good luck
 
J

jayprice7

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Jul 31, 2004
Messages
13
Re: '72 chrysler 70hp outboard failing at high speeds

this boat had been sitting outside in an illinois driveway for 2 yrs prior to me purchasing it. In order to get the thing started for the first time i had to use jumper cables from my car to get enough cranking amps to get the engine to turn over, but after that it has started just fine. It runs fine at low and medium speeds, and doesn't fail at idle. There was old gas in the tank.
 
S

scotiany

Senior Chief Petty Officer
Joined
Aug 3, 2002
Messages
749
Re: '72 chrysler 70hp outboard failing at high speeds

I think the first thing I'd do is replace the fuel pump diaphragm and go from there. That would be easy and cheap to do.
 
S

shipyard

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Jul 24, 2004
Messages
15
Re: '72 chrysler 70hp outboard failing at high speeds

Sounds a lot like what I've been doing. Eurolarva has great suggestions. Also most of the machanics I work with restoring boats tell me that if it's been sitting for a while rebuilds are pretty much a must to start out with. I just rebuilt my 55 carbs and fuel pump and it inproved performance like nighe and day.
 
eurolarva

eurolarva

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Joined
Jun 24, 2003
Messages
4,182
Re: '72 chrysler 70hp outboard failing at high speeds

I dont think either of those parts are the correct ones. Go to NAPA and get 18-7037 carb kit (15 bucks per carb) and get a 18-7806 fuel pump kit (9 bucks). They probably stock the carb kit and you will have to order the fuel pump kit. The pump kit takes about two days to get in.
 
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