question on dia and pitch choices

Hi guys,I currently have a 18.5 foot Steury v-518 with a 165 i6,boat weighs around 2100 and and the gearing is 1.65. The prop i currently run is a 14.25 x19p 3blade,,the prop has good top end ,but not much in the way of hole shot and has trouble maintaining in corners,also i do alot of tubing and skiing.At WOT with 4 people in it i get around 3800 rpms which seems a little low. When i got the boat it had the stock 15.5 x15p prop on it but was pretty bad shape so i bought 19p prop mentioned earlier. How much if any top end will i loose going back to the 15.5x 15p prop or would i be better to go with a 15.5x 17p? or 16p? I know if i stayed with current dia and went with less pitch the rpm would shoot up and i would prob loose some top end but what will the effects of bigger diam and less pitch be? will i loose a little top end and gain alot of holeshot and better cruise or will top end stay close and gain handling and holeshot and stability.Let me know your experiance.You guys are far better versed in the right prop selection than i am,,,thanks for any input.I have read several articles but cant seem to draw the right conclusion. Matt

Re: question on dia and pitch choices

I believe the 165 rpm range is about 3800-4200. lower than typical for other combinations.
With a light load I would think you would be about 4000-4200 with the 19.
I also think the 19" should produce more rpm.Your motor may be a little tired or perhaps needs a tune up with a compression check.
If you get us your wot rpm and gps speed it will help.Some cells have a gps app.
As things stand A 18" 4 blade should produce about the same rpm with better hole shot, stronger corners and improved handling around the dock.With some luck the top end may be about the same.

Re: question on dia and pitch choices

thanks steelespike,,,compression is great,,some question about the timing setting on it. i'm going to find tdc and put some tape on the balancer,then time it and also check that the mech advance is working properly,this old boat is heavy ,by myself i can get about 3900 out of it.if Im pulling a tube it just doest have the holeshot power i need to maintain. maybey thats why bit came with the big 15p ..again,,thanks for the info!

Re: question on dia and pitch choices

hey steelespike,,,since i would like to go back to a 15in prop would you reccomend going to a 17p 4blade due to the diam increase? id like to stay around 4200 at wot. thanks

Re: question on dia and pitch choices

Dropping a inch could add about 200 rpm. You may have to watch the rpm with a light load.
A 17" prop should act likes a 17" prop.
Usual diameter differences reflect the design.While diameter can affect rpm it is to a lesser degree
you could hardly tell unless a large difference. around an inch or more.
A 4 blade has more area so the diameter is usually reduced. Certain props have extreme diameter for specific applications like a house boat or a pontoon.Sometimes you see props with a 16" diameter.

Re: question on dia and pitch choices

So with my current prop at 14.25x 19p running at 3800 ,with a 15x17p 4 blade i would be theoretically around 4100? or 4200 with a 15x17p 3blade ,with the improved handling and better holding power and quicker plane award going to the 4 blade correct? Just maybey a couple mph loss with a 4 blade if any.sorry for all the questions,,just new to the propping game.