SailNet Community - View Single Post - overpropped vs underpropped
View Single Post
  #22  
Old 12-16-2012
MedSailor's Avatar
MedSailor MedSailor is offline
Closet Powerboater
 
Join Date: Mar 2008
Location: Anacortes PNW
Posts: 2,543
Thanks: 81
Thanked 53 Times in 45 Posts
Rep Power: 7
MedSailor is on a distinguished road
Re: overpropped vs underpropped

Quote:
Originally Posted by groundhog View Post
well, the engine seems to effortlessly move the boat as set up.
It reaches hull speed well before full throttle.

I just dont understand what being 250 or so rpm off makes any difference.
If I was well over propped, I could see re-adjusting. But they are going to force me to re-lift the boat now, well after they signed off on the boat when we could have easily made an adjustment.
Sizing the prop is like picking the correct gear on your 10-speed bicycle. I'm sure you can reach maximum speed in 10th gear on a flat road, but you'll need to put more force into it and you could stretch the chain and deform the bearings.

If you are in 8th gear on a flat road, the force required is less, though you need to pedal more RPMs to do it. You still reach your maximum speed but you haven't stretched the chain, deformed the bearings, or worn out anything else in doing so.

Your engine manufacturer believes their engine will last longer if it isn't working so hard and the only way to know how hard it is working is if you are ABLE to reach max RPM at WOT.

I hope this makes sense.

MedSailor
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


I have a sauna on my boat, therefore I win.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook