Spun Prop

[markwingert]

I have an Evinrude around 1963 18hp (18302e) with likely the original prop, it has a shear pin that is in working order and not damaged. My question is can a prop with a shear pin have a spun hub?

More background: motor starts right up not problem plugs clean, spits water but last year it would run around at 18mph and this year it will only do 8-9mph. At a loss other than the prop being bad/spun.

Am I missing anything that could cause this issue?

 

[jimmbo]

If the Pin is the correct one. it is not likely to shear, as it would be Stainless Steel. The Props will have a Rubber hub to absorb the Shock of shifting

Is the engine running on both Cylinders, at higher Revs?

 

[racerone]

Yes it has a rubber hub.

 

[Chris1956]

Yes, pin drive props can spin. The rubber hub goes bad. A lot of those motors had brass pins, however, that makes no difference to your issue.

Make sure she is running on both cylinders. The spark plugs should look about the same, if both are firing.

 

[F_R]

When the motor is running 8-9 MPH, is the engine racing or is it bogging like lack of horsepower? A spun prop would result in racing.

Anyhoo, it is easy to check the hub for slipping, Simply make a mark on the prop nut or just use the cotter pin as a "mark". Make another mark on the propeller, aligned with the first mark. Run the motor till the suspected slippage occurs. Now check your marks. If no longer aligned, the hub slipped.

 

[markwingert]

When the motor is running 8-9 MPH, is the engine racing or is it bogging like lack of horsepower? A spun prop would result in racing.

Anyhoo, it is easy to check the hub for slipping, Simply make a mark on the prop nut or just use the cotter pin as a "mark". Make another mark on the propeller, aligned with the first mark. Run the motor till the suspected slippage occurs. Now check your marks. If no longer aligned, the hub slipped.

Update: got a new prop and having the same issue still, so it is not a spun hub. It does seem like the motor is bogging down when running. it is running on both cylinders when running and seems to have good compression. What should I check next?

 

[markwingert]

Update: got a new prop and having the same issue still, so it is not a spun hub. It does seem like the motor is bogging down when running. it is running on both cylinders when running and seems to have good compression. What should I check next?

 

[saltchuckmatt]

Update: got a new prop and having the same issue still, so it is not a spun hub. It does seem like the motor is bogging down when running. it is running on both cylinders when running and seems to have good compression. What should I check next?

Carb or GOOD spark or both.

 

[markwingert]

Carb or GOOD spark or both.

I think maybe carb, there are two idle adjustments out by the kill switch. one for low speed idle and one for high rpms I believe when I adjust them nothing happens at all. I can turn them all the way one way or the other and it seems to make no difference at all...

 

[saltchuckmatt]

I think maybe carb, there are two idle adjustments out by the kill switch. one for low speed idle and one for high rpms I believe when I adjust them nothing happens at all. I can turn them all the way one way or the other and it seems to make no difference at all...

You didn't seem to have any problems on the low end so you shouldn't have touched that one.

Did you try the high speed when you were out bombing around?

 

[jimmbo]

Back to the beginning
What are the Compression Numbers?
Does it have a Spark that can jump a 7/16" gap consistently, on both Cylinders?
Is the Fuel System in good condition, no air or fuel leaks, Clean Filter/Screen, on motor and on pickup tube in the tank.
Is the carb opening fully when the Throttle is at full?
Try resetting the Mixture Needles on the carb. Top one, 1 1/2 turns out from lightly seated. Bottom one, 1 turn out from lightly seated. Both of these settings are usually quite Rich, but will permit the engine to start and run.
Adjust the Bottom one first. At WOT, adjust for highest Rpm. Your ears are a Good Tachometer for that. Then at idle adjust for best idle in gear. Recheck the High Speed Adjustment.

 

[racerone]

Sounds like it is running on just 1 cylinder.-----Remove flywheel.----Inspect / clean breaker points.----Test and see if spark jump at least 5/16" on both leads.

 

[F_R]

I think maybe carb, there are two idle adjustments out by the kill switch. one for low speed idle and one for high rpms I believe when I adjust them nothing happens at all. I can turn them all the way one way or the other and it seems to make no difference at all...

If turning the needles all the way makes no difference at all. they are not actually going "all the way". It shouldn't run at all with the high speed knob turned all the way in. I suspect the knob limiters are preventing enough range. Remove the knobs and set the needles to best running position, high speed first. When you are satisfied, reinstall the knobs.