Prop question

[jsaylor]

2005 crestliner pro angler 1650 50hp tldi nissan. Have a 11 pitch wot about 5200, at 25 mph, also have a 13 pitch wot 4800 rpm 29 mph. These are figures with two people in the boat, add two more adults and can't get on plane with the 13 pitch. It seems perhaps I should get a 12 pitch? or might you suggest a 4 blade? if so what pitch? the 13 pitch is a solas rubex performance seems ok however lots of prop chatter no matter how much torque I use, from just snug to 25 foot pounds?
Thanks so much for any help. Also any opinion on brand of prop? my 11 pitch I can't find a brand name, the 13 is a solas.

 

[Jgcrock99]

Personal experience, I struggled with my 4 blade and pretty much stopped using it. My set up is completely different so may not be the same result for you. I have a 19' Chaparral bow rider with the 220hp 4.3. I was interested in a 4-blade for towing and did my prop research to find how the performance responded to different changes. Pitch change and blade change are abiut the same. 200rpm drop when adding a blade and 200rpm gain when reducing pitch per inch. I was running a 3-blade 21p and hitting about 5k. I tried a 4-blade 19p and could barely make the bottom end of my Rev range and even worse with more than 4 aboard. Dropped to a 17p and it helped but I eventually returned to my 3-blade 21p and performance has been much better. Again, very different set ups for both of our vessels but wanted to share.

 

[jsaylor]

What brand 4 blade?

 

[jimmbo]

First of All, what is the WOT Rpm Range for your Engine? What condition is it in Mechanically?

 

[dingbat]

2005 crestliner pro angler 1650 50hp tldi nissan. Have a 11 pitch wot about 5200, at 25 mph, also have a 13 pitch wot 4800 rpm 29 mph.

Looks like your WOT range is 5150 to 5850.
if that's true, you're 400-500 rpm shy of where you want to be
What diameter is that 11" prop?

These are figures with two people in the boat, add two more adults and can't get on plane with the 13 pitch. It seems perhaps I should get a 12 pitch? or might you suggest a 4 blade?

A 4 blade is going to make things worst.

if so what pitch?

If your go with the rule of thumb, 200=1, you need to drop down to 8 or 9" prop. Don't know that they even make prop that size.

 

[jsaylor]

Prop diameter is 11.1X11, noticed my cavitation plate is about 2 inches below the boat, do you think raising the engine 1 inch would increase my rpm much?

 

[jimmbo]

Prop diameter is 11.1X11, noticed my cavitation plate is about 2 inches below the boat, do you think raising the engine 1 inch would increase my rpm much?

Probably by a 1 or 2 hundred Rpm, more if Air gets in the the Prop. You boat is a Tin Boat, with no Rivets on the Bottom of the Hull? Is there a Keel Extending all the Way back to the Transom? If not, you should be able to Raise the Motor until the Anti-Ventilation Plate is Even with the Bottom of the Hull