1972 Chrysler 20 hp Runs intermittently

[Wilsonsk1966]

I took it out on the lake last night, it started ok at the landing, 3-4 pulls, it was pretty sputtery through the no wake area but ran good WOT, it pushed the Lund deep 14 at 20 mph. I ran it for a mile and then slowed down and ran at no wake speed for a bit, still kinda rough but didn’t die. I shut it off and fished for a half hour or so. When I tried to start it it started hard, 10 pulls or so, it fired once first pull and then nothing, after 8 pulls or so I tried priming it, then a couple more and it started. It ran good, I ran WOT the mile or better to the other end of the lake, then I slowed to no wake speed, 3-4 mph, and adjusted the low speed screw a little and it runs pretty good at real slow speed but rough at mid speed (8 mph or so). I stopped and fished for 20 minutes or so and when I left I primed it and it started on the first pull, ran great all the way back and idled through the no wake area really well. Seems like it might be losing prime on the fuel pump, I have a kit so I’m going to rebuild the pump.

 

[Wilsonsk1966]

I'm hoping someone see's something I'm missing, please feel free to suggest anything, I feel like I'm sort of getting there but I also don't feel I'm there yet, I'm going to do another decarbonizing process or 2 today, not sure if I'll get it on the lake or not, but I think running it should help too.

 

[Wilsonsk1966]

I did 3 decarb treatments with sea foam, probably upset the neighbors, it sat for a few days and started today on 3 pulls, took it to the lake, it is a 1/4 mile or so of no wake and it was intermittently dropping a cylinder, I hit the open water and opened it up, it took off well, ran 22 mph for 10 minutes or so then lost power like a cylinder dropped, it still ran but sort of smooth with half power, pumping plenty of water, I got it home and checked spark, still nice and blue, had 80 psi compression in the top, 30 in the bottom. I’ll pull the head tomorrow and see what I see.

 

[Wilsonsk1966]

Hopefully this has been the problem most of the time. Both the upper and lower have been leaking, the lower blew last night, I have one on the way.

 

[Nordin]

I would suggest you to change the impeller too if you have not done it.
Looks like it has run hot.

 

[Wilsonsk1966]

I'll check it, I know the PO had just put impeller and new housing right before I bought it, he gave me the old parts, he knew he had it hot before that and they did a compression test and thought the motor was ok, I need t ideal up the LU anyway so I'll look at the impeller, I don't think I ever had it hot, I thought I did early on but in hindsight now I don't think so.