125hp –72’ Johnson...fIre, fuel, air, cooling?

Let me start out by thanking everyone for all the information ya’ll post. I’ve been reading this board for a while now and it’s helped on many occasions.<br /><br />I have a Johnny 125 -72’model on an old 72’ tri-hull. I fish out of it several times a year with no problems. (Here comes the but…)But; we recently got a pull tube for the kids and on the only two occasions I pulled the tube after fishing in the morning this problem occurred. After pulling the tube for 45 minutes to an hour I stopped the motor and the kids swam for 20 to 30 minutes. Touch the key, the motor starts, I put it in gear and it dies as I slightly throttle up. Touch the key, the motor starts, I put it in gear and it dies as I slightly throttle up, on and on. Took the plugs out when I got home and they looked normal. I’m using a standard 50:1 gas mix.<br /> After the first time this occurred, I buffed the plugs off and barrel tested it, and went fishing the next weekend and it ran good. It kept running good for several trips up until I pulled the tube again. I’m using the recommended plugs and gap. Most of my fishing runs are 15 to 20 minutes. Could something be getting hot? T-stats? Water restrictions ? I put a new water pump in this past winter. I can fell warm water down at the vent in the lower unit when the t-stats open, when I run it on muffs. Any ideas ?<br /><br />Thanks, BigTim<br />125hp –72’ Johnson<br />40hp –97’ Johnson<br />9.8 – 85’ Mercury<br />3hp –63’ Evenrude

Re: 125hp –72’ Johnson...fIre, fuel, air, cooling?

On this engine, I would start with a compression test. If you see a difference of over 10#, pull the heads.Infact! I would pull the heads to start. This was a good old engine, but! it's 32 years old. I have been running this same engine for years, but it has been over the shop bench more than once. Check to see that your temp. warning horn is working, could need a carb. rebuild.

Re: 125hp –72’ Johnson...fIre, fuel, air, cooling?

When it dies have you tried pumping the primer bulb until it gets hard? From your description I would suspect a fuel issue - maybe it is time to rebuild the carbs.