Speeds at Wot

[damianfishy]

Hello, first post on this forums after browsing for the last few weeks,

Took the boat out yesterday Galaxy 19, Mercruiser 470 Alpha one drive, It ran perfectly no hiccups stayed at a steady 160 all day, The question I shall be asking is to do with the Prop, I'm currently running a 21p SS on it and yesterday I was topping out around 35 Mph with 2 people, This was at around 4700-4800 Rpms it seemed like it could pick up alot more Revs
If i let it stay there but obviously didn't push it, When i bought the boat It came with the 21p SS on it and came with a couple more Props which was a New 23P SS and a 23P Aluminium, question is would the 23p SS give any better top end speeds attal?

I can't get on the water to much maybe 1-2 a month due to weather in England not being the best but yesterday was a flat calm day on the sea so allowed me to have a smooth ride


Thanks

 

[alldodge]

Re: Speeds at Wot

:welcome: to iboats, yall

England is a perty fer piece for Kentucky. I know don't quit my day job, comedy is something I should stay away from.

:focus:

Your Merc's WOT should be from 4200-4600 RPM, you currently are over reving at your posted limits, this can damage your engine.
For every increase/decrease in pitch you will increase/decrease 200 rpm. That being said 22 pitch should be the best but if you make sure to not over-rev the 21 will give you better hole shot. The 21 should also allow you to carry more load and still operate smoothly. The 23 pitch will work and will keep you from over reving.

 

[damianfishy]

Re: Speeds at Wot

Thanks for the response, I didn't run it for long at 4800 about probably 20 seconds then dropped back down, I may try the 23p when I get a chance to get out there, also at around 4000 rpms it goes along at a steady 30 mph, meaning the 600-700 rpms only gained 4-5 mph does that sound about right?

 

[alldodge]

Re: Speeds at Wot

Thanks for the response, I didn't run it for long at 4800 about probably 20 seconds then dropped back down, I may try the 23p when I get a chance to get out there, also at around 4000 rpms it goes along at a steady 30 mph, meaning the 600-700 rpms only gained 4-5 mph does that sound about right?

Sounds about right to me
Also forgot to mention, stainless props don't flex much and therefore give you pretty good bite with less slip. The aluminum props bend some so they, lets say start at 23 and end up around 22 or so. If you hit something in the water hard and you have a stainless prop on, it will probably damage your drive. If you have an aluminum prop you can usually get by with a new prop. With that your insurance will cover either if coverage is sufficient