1977 Chrysler 15 hp cuts out at high rpm

[Jonvk]

Help needed. I have a 1977 15 hp chrysler that runs fine for 15 or 20 minutes then starts to cut out at full rpm's. Acts like I'm hitting something, or not getting enough fuel. I have just replaced the fuel pump components and cleaned the carb. It has electric start, so there are lots of wires.
Please let me know if anyone has any good ideas of what could be wrong.
Thanks,
Jon

 

[foodfisher]

Re: 1977 Chrysler 15 hp cuts out at high rpm

Might be air leaks at hose connections, water in fuel...

 

[fucawi]

Re: 1977 Chrysler 15 hp cuts out at high rpm

fuel cut outs tend to be soft whilst electrical sharp.....is the primer bulb flat ? does it start straight again away?

 

[Jonvk]

Re: 1977 Chrysler 15 hp cuts out at high rpm

Fuel line connections are all tight. It is a duck boat and my dog was all over, the water would have had gone in the vent hole of the gas tank. Thanks, I will check that.

Primer bulb was hard all the time, but my fuel filter will not totally fill up with gas. Not sure if it is suppost too. Could be sucking air from that. It was that way while it was running fine for the first 15 minutes.

 

[fucawi]

Re: 1977 Chrysler 15 hp cuts out at high rpm

Turn the filter vertical and get the air out ..I assume you mean an auxilary filter...water in the gas ..lift the pick up pipe off the bottom of the tank ..dont think its that myself.

does it start up straight away and run another 15 min ??

 

[Jonvk]

Re: 1977 Chrysler 15 hp cuts out at high rpm

yes it is an auxilary in-line filter from FRAM. The internal fuel screen was cleaned when I rebuilt the fuel pump.

It never quits as I just throttled down to keep it running. If I run it at half to three quarter throttle, it runs fine.

 

[fucawi]

Re: 1977 Chrysler 15 hp cuts out at high rpm

well as you go faster you need more HT voltage and you need more fuel ..if you pump the primer bulb every 15 seconds and it still cuts out then it sounds like igniton to me ......

 

[Jonvk]

Re: 1977 Chrysler 15 hp cuts out at high rpm

I thought i would change the spark plugs just in case. I had it out on the water twice since I had pulled the plugs and wire brushed them. See pictures showing the lower plug fowling. This would be my problem with why it was cutting out, but now, what would cause this to happen to the plugs. They appear to be getting to hot. I am running 50:1 Any ideas?
View attachment 115887View attachment 115888

 

[fucawi]

Re: 1977 Chrysler 15 hp cuts out at high rpm

well your attachment did not work .you should go advanced and use the paper clip symbol and do photos properly ....if you are using the right plugs then they cannot get too hot unless the timing is over advanced or the mixture weak. The engine runs on the idle system up to about 2/3 throttle so you could have a carb problem with the main jet or float level ....now we get close to the problem I think

 

[Jonvk]

Re: 1977 Chrysler 15 hp cuts out at high rpm

see pictures attached. The plugs that were in there were Champion L-4-J
The guy at our local marina told me to use L82C