1975 75hp Chrysler Outboard died

Joined
Apr 1, 2014
Messages
2
Hello All,

I am a complete rookie when it comes to fixing outboard engines. I am, however, mechanically able to do so. Last summer I took my boat (1988 Rinker Shoreliner) out fishing with friends. The engine (1975 75hp Chrysler) started and ran fine for about an hour. We decided to fish another spot on the Detroit River and while heading there, full speed, the engine quit, and the boat came to a sudden stop. The engine turned over, but nothing for about 5 minutes. When it finally started the engine ran like crap (shook). I was running the throttle about 3/4 open, but the boat only did about 5mph. The engine would die off and on (running at 3/4 open only doing about 5mph). Also, at times, when running at 3/4 throttle the engine would accelerate to "normal capacity" at 3/4 speed (about 20mph). The engine finally quit after reaching the boat dock. It has not started since. To me it seemed as though it was running on 2 cylinders rather than the 3? I have been told it may be an issue with the fuel lines? I would like to get some better incite before tackling the fix. Any advice would be greatly appreciated.
 

Adw

Cadet
Joined
Apr 1, 2014
Messages
6
Re: 1975 75hp Chrysler Outboard died

There are a few things you should test. First compression on each cylinder, you can get a compression tester at the autoparts store. First unplug all three plug wires, take one spark plug out and screw in the compression tester and crank the starter (good compression should be close to around 120). Go through all three holes if one is low or no compression then you found the problem. If all cylinders have good compression, check the spark. Again a spark tester for the auto parts store will be fine. If all three wire give you a good strong light then move on to the fuel system. You probably have three carbs in a series. One way to test this would be to take either 3 new clean spark plugs or just clean your existing plugs reinstall them fire up the engine run it at 3/4 throttle for a few minutes shut it down and check each plug. Pull one at a time so you don't loose track which plug came from which cylinder. Look at the plugs there should be some soot and they should have a fuel/oil smell go through each hole the cylinder not getting fuel will be clean and have no smell of fuel/oil. Then look at that cylinders carb. Try this out hopefully you will find the problem somewhere along the line. Hope this helps.
 

MickLovin

Master Chief Petty Officer
Joined
Feb 18, 2013
Messages
822
Re: 1975 75hp Chrysler Outboard died

When you check compression make sure you ground the spark plugs, it actually sounds like an electrical problem, are you getting spark to all spark plugs. Also check your fuel diaphragm and bowls of your carbies for any debri that may have come through the fuel system, it doesn't take much to block a jet up. Do you have a filter in between your pump and your carbies?
 
Joined
Apr 1, 2014
Messages
2
Re: 1975 75hp Chrysler Outboard died

ADW,

Thanks for the input. I finally worked on the engine today. I bought new spark plugs and cranked the engine. It ran for about 20 seconds then died. This happened a couple of times. I squeezed the ball on the gas line and it never got hard. Isn't it supposed to get hard after a couple squeezes? Guess I'll try replacing that line/pump. I do have a fuel filter which is attached to the side of the engine. I took it apart and no debris found on the metal screen type filter. I did check compression and was getting 120-125 readings, so fine there.
 

MickLovin

Master Chief Petty Officer
Joined
Feb 18, 2013
Messages
822
Re: 1975 75hp Chrysler Outboard died

Ok your compression sounds reasonable for a 75hp which are specced at 130 - 140, I have had two of these and it sounds like a fuel pump diaphragm after your last comments. The inline or right angle filter should be in between the fuel pump and the carbies. The fuel pump diaphragm can look alright, but I have had ones with pin holes in them, this allows to much fuel into the supplying cylinder/crank, giving it a flooded appearance. Check your spark plugs, they are more than likely running black from the excess. Clean your plugs, make sure you have spark on all, then check that fuel pump diaphragm, also drop the top carbie bowl with a white rag under and have a look if there is much rubbish in your carbie from a detiorating diaphragm, fuel line etc. Also check you have no water in your tank.

I would start from the tank and work back, but a primer bulb not getting hard is either a fuel pump diaphragm or an air leak in fuel delivery system (e.g. tank, tank pick up, fuel line to primer air leak, air leak after primer) Check all your hoses for any perishing, they do perish from the inside out as well.

If it was running fine before then suddenly you started having problems, DON"T touch your carbies air mixture, it is more than likely set right, however the carbies would be set at all the same turns. If you are going to touch your carby settings read Franks link and sync sticky at the top of this forum.

My bet is fuel diaphragm, I would nearly put money on it :D
 
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