1970 thunderbolt HELP

[Ben Pearson]

Looking for some help. I purchased a 1970’s not sure exact year 50hp thunderbolt. The person I bought it from said he has no idea if it runs. So far I have checked compression 130 psi on all 4 cylinders. I replaced the fuel line and new primer ball. Rebuilt the fuel pump. Completely rebuilt both carbs replaced a bunch of suspicious wires. I check coil and tested all spark plug wires. All 4 plugs sparking. Timing is dead on. The spark plugs do not show any signs of water getting into the cylinders. When it is in the drum it idles perfect. When in neutral throttles up. When in the drum it goes into gear perfect and throttles up and empty’s the drum in seconds. Here’s the problem. I’ve been to the lake 3 times. It won’t throttle up in gear in the lake. I can put it in the gear and putter around with no stalling. I’m starting to think this motor is afraid of deep water.

 

[racerone]

Open low speed mixture screws 1/8th turn at a time.----Bogging will like go away.

 

[Ben Pearson]

Thank you for the response. While I was in the lake I adjusted the mixture screws on both carbs. I opened them up until the motor was running rough the closed them until it ran smoothly at idle. It just doesn’t seem to want to throttle up in gear.

 

[racerone]

Checked belt timing?-----When you replaced the impeller did you check for plugged exhaust passage way ?

 

[Ben Pearson]

I did check the belt timing but didn’t check for blockage. Would that cause the motor to trottle up in neutral but not in gear?

 

[Droid]

Since the idle mixture screws on each carburetor seem to make a difference, maybe one carb is plugged up on the main circuit.

 

[Ben Pearson]

I did completely take the carbs apart and cleaned them out. I was at the water today for one last try before winter. It still didn’t go. When I removed the plugs at the lake and they did look wet. When I came home I pulled the covers off the block. It looks like some water could be getting in there. I think I’m going to spend the winter learning a bunch more about this motor while I rebuild it. Thanks for all your suggestions.