Low Power, Low RPM

I am trying to revive a 1975 Chrysler Force (Challenger) 90 Hp. The motor has not been running since about 1994. I have cleaned the carbs and checked the compression. (1 - 130, 2 - 125, 3 - 120). The water pump was checked and replaced. The motor starts and runs good in the driveway, (with a water hose).

When I get it to the lake, I cannot get it above 3000 RPM, and it struggles to get there. The pontoon boat will plain out but the motor surges and does not run steady at WOT.

After running the motor for 30 min on the lake, the center plug looks clean but wet. The others are brown and wet. I am not sure why only one plug would not consistently be getting spark with a one coil setup like mine. I measured the resistance/continuity of each wire at 8K-9K, from the boot to the inside of the distributor cap. I have visually checked for spark on each wire, with an adjustable spark tester, although the #2 looks weaker than the others. I have cleaned the inside of the distributor and checked the points.

Any Ideas?

Was the motor always on the pontoon boat?
NO? then the prop could be part of the problem??

The surging could be the fuel pump.
The wet plug could be the fuel pump.
The diaphragm could be bad??
#2 cyl operates the pump and if the above is a problem??
Then check the pump.

I agree with jerrry,a possible dry rotted fuel pump diaphragm and/or fuel restriction, Have you tried pumping primer bulb when this issue arises?

johnnygjr said:

I agree with jerrry,a possible dry rotted fuel pump diaphragm and/or fuel restriction, Have you tried pumping primer bulb when this issue arises?

Click to expand...

I will check the Fuel pump, diaphragm. No I have not tried to squeeze the primer while under load. I will check this too. One thing i did notice with the fuel system, is that if I pump the primer with the engine off, the fuel would flow through the carbs and out the exhaust. I had about a gallon of gas wasted on the ground once, because I did not remove the fuel line from the tank on a warm day.

The motor has been on this pontoon for as long as I can remember. It was cobbled together by my uncle and an outboard mechanic that lived across the street. This 1975 motor is on a 1986 boat, the boat/trailer has been sitting on blocks in the yard, since my uncle passed in 1994. I believe this is the only motor that has ever been on this boat. I have been through the lower end checking bearings and seals, cleaned the carbs twice to be sure the fuel system is clean.

It runs great in the yard, starts easy after warm up. Just not running well under load.

I just found a late model 4 stroke motor that I may use to re-power the boat, and this one will be for sale if any one is interested.

If you squeeze the ball and it comes out the carb??
Then the needle/seat isn't working right.
And do check the diaphragm in the pump.

Jerryjerry05 said:

If you squeeze the ball and it comes out the carb??
Then the needle/seat isn't working right.
And do check the diaphragm in the pump.

Click to expand...

I have not had time to check the diaphragm yet.
The fuel does not come out the carburetors when I pump the primer bulb, (or when running in the driveway). The gas does seem to go into the crank case, mabey/probably through a crack in the pump diaphragm. I did not know that the fuel pump worked off of the second/middle cylinder.

When I did squeeze the primer originally, to get the fuel to the pump,the primer bulb did get firm but, it is still easy to continue to push the fuel somewhere. This is different than my other outboard, it gets very stiff once the fuel was to the pump/carbs.

I thought about the needle/float valve too, and originally thought they were the problem. The engine does not seem to get flooded when starting or running in the driveway.

I have this on a 24' pontoon. I cannot easily reach the motor from the cockpit while under way, or in the water.

If the ball doesn't get hard?
Then it's most likely the pump.