Prop replacement after hitting a rock results in low RPM?

[EpicMaltandBraun]

We hit a rock with the prop of our Mercury 135 HP outboard. The numbers on the prop said 19 pitch. We bought a 14.5 x 19 pitch and it matches the old Prop exactly. The engine used to run WOT at ~5000 RPM and now the boat won't plane and the RPM won't go above 3000 RPM. We checked that the shaft wasn't bent and it isn't. What else could we have damaged when hitting the rock that could cause this? The engine runs smooth. What else can cause this? Is it coincidence?

 

[steelespike]

Re: Prop replacement after hitting a rock results in low RPM?

The throttle cables could be damaged or knocked out of adjustment,The motor linkage could be whacked,a plug wire may have come off.
You wouldn't be the first to not realize you were missing a cylinder except for the loss of power.

 

[Frank Acampora]

Re: Prop replacement after hitting a rock results in low RPM?

Depending upon year and design of Mercury: Did you remove the thrust washer from the old prop and replace it into the hub of the new one? Frequently the thrust washer will corrode into the old prop hub and look like a part of it. Then, unsuspecting owners will replace the prop without using a thrust washer. The prop will ride against the gearcase casting with resultant drag.

 

[Bamaman1]

Re: Prop replacement after hitting a rock results in low RPM?

+1

You've got something else going on here. It's probably something small.

 

[EpicMaltandBraun]

Re: Prop replacement after hitting a rock results in low RPM?

Thanks for the replies. You were right we did have something else going on. The vibration from heading home with the bent prop made the screw attaching the throttle cable to carb #2 fall out.. The other two carbs screws were loose as well.

Thanks again!!

 

[steelespike]

Re: Prop replacement after hitting a rock results in low RPM?

Isn't great when a stab in the dark works.