Slow start?? New battery, cables, starter, solenoid

[cameronr]

1975 Evinrude Model #50573B 50HP 2 Stroke.

I am trying to get this old boat running and having problems getting the engine to crank with the spark plugs in. With the spark plugs removed, the engine cranks without problem (no compression) with 1 spark plug in or 2 it will crank very slowly either cylinder. Almost like a sputtering.

I read through many forums before posting and non seem to have went over this specific cause.

I have replaced the
connecting wires
battery
starter
solenoid.

I have tried 2 high cranking batteries which are fully charged and healthy and power my 70HP. So that is not the issue. I have also tried jump starting the boat directly from the sylinoid and starter with 2 sets of jumper cables and a new 4 gauge wires, same results. From what I am gathering it almost feels like there is too much compression. I know the engine is not seized because the flywheel spins freely and is not locked up. Same with the boat being in neutral as it cranks without the spark plugs out.

I am lost as to where to look next, my initial thoughts were to drop the lower end and maybe something is clogging the exhaust? Where would you start?

 

[Crosbyman]

Same with the boat being in neutral as it cranks without the spark plugs out.
I know the engine is not seized because the flywheel spins freely

that said why not drop the LU/GC and retry

btw doest idle ok when started in neutral ? one would not normally start in gear anyway and it should not start anyway with neutral interrupt

 

[cameronr]

Same with the boat being in neutral as it cranks without the spark plugs out.
I know the engine is not seized because the flywheel spins freely

that said why not drop the LU/GC and retry

btw doest idle ok when started in neutral ? one would not normally start in gear anyway and it should not start anyway with neutral interrupt

I will try the lower unit tomorrow, and see if that does anything. Not feeling optimistic as it doesn’t seemed locked up unless it is an air issue.

I apologize, I meant the boat is in neutral l when trying to start it, it does not do anything in gear.

 

[Scott Danforth]

Did you clean all the battery cable connections and the starter mounting pad?

 

[cameronr]

I dropped the lower unit, and the motor is still not spinning. I am bypassing everything and starting it directly to the starter with a fresh battery: It will spin but very very slowly. (Almost like “clank clank clank clank” it almost feels like TO much compression. I haven’t done a compression test.

Not sure where to go from here.

 

[dingbat]

I dropped the lower unit, and the motor is still not spinning. I am bypassing everything and starting it directly to the starter with a fresh battery: It will spin but very very slowly. (Almost like “clank clank clank clank” it almost feels like TO much compression. I haven’t done a compression test.

Not sure where to go from here.

Remove the starter from the motor and bench test with a fresh battery.

If its still doesn't "jump" to life you have a bad starter.

 

[tblshur]

Have you tried to put a little gas in the cylinders see if it will hit if that doesn’t change anything take plug wires off and try it also make sure plug wires are not crossed just a thought

 

[tblshur]

Is that a new starter or just a different one

 

[tblshur]

Will the starter on the 70 fit it

 

[cameronr]

Remove the starter from the motor and bench test with a fresh battery.

If its still doesn't "jump" to life you have a bad starter.

Starter spins hot and fast when bench testing and with the spark plugs removed

 

[cameronr]

Is that a new starter or just a different one

It is a new starter, the 70hp does not fit as the positive plug is on the wrong side

 

[stresspoint]

put the plug wires on the correct plugs .

 

[flyingscott]

have you done a compression test?