Please help select a replacement prop

[w_huisman]

Answers to the questions in the sticky thread at the top of the forum are:


1) Performance issue you are trying to correct. – Our stainless prop has rock dings, and the hub is shot in our aluminum one. Both are three blade props. We would like to significantly increase hole shot with a new prop, even if we have to give up some top end speed.

2) Current prop manufacturer, model, aluminum or stainless as a minimum. – Unsure of manufacturers or models.

3) Current prop diameter and pitch (required). – our stainless prop is a (14.5 x 21-M1), our aluminum is 13.75 x 21

4) Wide open throttle RPM and speed with an average load (very helpful) – Typical top GPS speed at WOT is 45mph (depending on trim) at ~5200 rpm. The RPM range listed for this motor is 4500 – 5500.

5) Engine/drive make, model, year, and HP – Yamaha VMax HPDI, VZ150TLRB, 2002, 150hp, manufactured in April 2002.

6) Boat make model, year, length and weight- 2004 Yar-Craft Cobra 192DC, ~19 feet long, Manufacturers listed weight is 1600lbs, plus the Vmax listed above, plus a Yamaha T8 kicker, plus a 50-gallon fuel tank, plus 500lb worth of people.


We really want a new prop that increases our hole shot and gets the boat on plane as quickly as possible, but can also hold the bow in the air if needed in big water. We are thinking that a 4-blade stainless would be the ticket. However, we have no experience with sizing props, so we have no idea what pitch, diameter, or number of blades would be best for our application. Any insight you can provide would be appreciated!


OUR BOAT:

OUR PROP:

 

[steelespike]

Re: Please help select a replacement prop

assuming a 1.85 gear ratio your slip seems a little high.
Maybe from the dinged prop.
You might consider trim tabs these will get you out of the hole and when retracted will allow max wot speed.When set righjt can smooth a rough sea.

 

[w_huisman]

Re: Please help select a replacement prop

Thanks Steelspike. What is "slip"? If it is calculated from the 5200 rpm i posted above, i admit i was guessing at that number a little.

We will be buying a new prop, so do you recommend we get the same pitch and diameter?

 

[ratherbeboating]

Re: Please help select a replacement prop

trim tabs are a good idea but are expensive. there are other less expensive options, such as doel-fins, that attach right to the cavitation plate that i have used in the past and seem to help. also if you decrease you pitch to a 19, you will gain a better hole shot but you might lose some top end and your wot will be closer to your limit. if you are running in rocky waters i would reccomend an aluminum prop as to minimize damage to the gear case upon impact. finally before you do any thing check your prop shaft to make sure it is not bent and check your gear oil for metal shavings to make sure no internal damage has occured. good luck and happy boating.

 

[w_huisman]

Re: Please help select a replacement prop

Thanks! So to gain hole-shot we should go down to a 19. How about diameter?

 

[ratherbeboating]

Re: Please help select a replacement prop

diameters change with blade configurations depending on the prop design and the manufacturers. your local dealer should be able to help you out with a specific prop type. some manufacturers offer four bladed aluminum props too which in diameters will vary from three bladed ones. prop selection is hard but your best bet is a dealer who has your type of boat and motor and they should be able to offer you the best narrowed down selection to suit you. good luck.

 

[steelespike]

Re: Please help select a replacement prop

Do you have the actual rpm.Without actual rpm and speed you shouldn't be making a prop selection.I don't usually go for the tabs but you wanted to improve hole shot but wanted the ability to keep the bow up. The fins can improve hole shot cheaper but will make it harder to keep the bow up.They also tend to lower top end speed and reduce mpg.
trim tabs will get you up quick yet give full top speed and mpg when retracted and can be lowered to improve ride into rough seas.You can get the present prop repaired likely getting back to its intended performance.
Reducing pitch does improve hole shot and stay on plane with less throttle fiddling, top speed could be reduced depending on the present rpm.

 

[w_huisman]

Re: Please help select a replacement prop

Alright. Well, thanks for the help anyway. I'll probably just get the darn stainless one fixed. Too many variables to figure out how to get what I want.