1970 Chrysler 85 HP Issues

[michaeljbaker55]

I took my Chrysler motor out for the first summer outing on Friday. I noticed leaving the ramp, my motor was not running right. I left out of the no wake zone and got up to top speed and the motor died after about 30 seconds. I was able to move just above idle into a cove, to anchor off and drink some cold beverages. After two hours I got back into the boat and moved out of the cove and tried again to move across the lake at top speed. It died again and did not start. My buddy towed me into the ramp and we put it back on the trailer for the night. The next day I backed the boat in and started the motor to see how it would run while still on the trailer. The motor started right away but at very high idle and then would bog down for a few minutes and then back to high idle again. I decided to take it out on the lake close to the ramp. As soon as I would move above idle to get anywhere fast, it would immediately bog down and die. As long as I stayed a pinch above idle it would get me were I needed to go but, very slow. I started the day with fresh mixed gas, with Stabil, and enzyme fuel treatment. I need some help trying to figure this out. Next time I get a chance to work on it, I will be checking the timing and the belt on the distributor. I have thought about changing the fuel pump diaphragm to see if that may help out the bogging down issue at full speed. Any advice would be much appreciated!

 

[Nordin]

Michael some qustions to clarify what we are dealing with. Is this engine new to you? Have it run without issues recently?

For what you are describing it sounds like a fuel issue.
Start with checking the fuel pump diaphram, hoses from tank to pump and from pump to the carbs.
If the engine has seat for some years then you have to check and clean the carbs.

 

[jerryjerry05]

Check the compression and spark.
Then check the linkage for full travel.
Run it without the cover, possible the exhaust boot in the mid section has gone bad??

 

[michaeljbaker55]

Nordin,

The motor has been in my family since 1970. I inherited the whole rig from my grandfather when he passed away. Last summer, the engine ran fine except for running at full throttle, it would bog down and almost die after a minute and a half at full throttle. The longest the engine has sat since rebuilding the carbs was about 6 months. I plan on cleaning the carbs up and checking the diaphragm next time I get a chance to work on the motor. Thanks for the advice!

 

[michaeljbaker55]

JerryJerry05,

i am an aircraft mechanic and do not have a ton of experience with marine motors. How do I go about check compression and spark? Which linkage are you referring to? And what boot in the midsection? Thanks for the advice, just need some clarification.

 

[kbh121956]

There are video's on YouTube that will show you how to perform a compression check and spark testing. You can rent the tester at AutoZone if you don't own one. The linkage that Jerry is referring to is the cables from your control box, where they are hooked up on the motor itself. The boot is a small rubber corrugated tube with a spring inside it that is between the exhaust housing on the motor where the water comes out from. It's about 14 inches below your bottom spark plug. Also at the top of this forum there are some "sticky" video's that will show you how to ground out your sparkplug wires so not too damage your electronics. Jerryjerry05 will also answer your post by tomorrow morning. I hope that this helps you.

 

[jerryjerry05]

Running at full for 1 1/2 min then dying: could be the tank vent is clogged, there is an air leak at the inline fuel connectors?
the fuel pump could be bad?
Maybe your overheating?