Twin Volvo 3.0 HIGH plane RMP Problems

[gbratk]

Hello

I have Crownline 268 with twin volvo penta 3.0 gas engine and sx-m drives with 2.18 ratio (i think) and 14,5x19 ALU props.

I put the boat in the water today and It starts planing at 4000rpm! this is aroud 23 mph. the wot RPM is over 5000 rpm!
What should I do??? Are the props with wrong pitch ??? If I buy new props, what pitch to chose? I don't want to buy wrong props.

Please give me some help!

Thank you

Best regards

Gasper

 

[Bondo]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

I put the boat in the water today and It starts planing at 4000rpm! this is aroud 23 mph. the wot RPM is over 5000 rpm!
What should I do??? Are the props with wrong pitch ??? If I buy new props, what pitch to chose? I don't want to buy wrong props.

Ayuh,... That would be My Guess,.... I'd think 21" props might be big enough,...

Maybe not...

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Ayuh,... That would be My Guess,.... I'd think 21" props might be big enough,...

Maybe not...

That is the problem... maybe will enough maybe not. I don't want to buy wrong props.

How many RPM will drop with changing 19p to 21p or 19p to 23p?

 

[Bondo]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Ayuh,.... The rule of thumb is 200 rpms per inch,...
but,...
rules of thumb are just that....

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

I think, that I'll find two 21p props, but it will be RH and I have LH and RH.
So if I change in the Shifter command that the booth drives rotates in one direction I could test it with two RH props. Isn't it?
But what is the difference if I have LH and RH prop, between two RH props?

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Todaj I test it with 14 1/4 x 21 props, now I have 23mph at 3800rpm, ant WOT is around 5000 rpm. And it takes around 8 secunds, to get it on plane. So will be the 14 1/2 x 23 the right props? Is it possible that they will be to big?

Plese help.

Thank you

 

[Maclin]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

I am getting 33% slip for 23mph at 3800rpm from a prop calculator. What is the mph at the 5000rpm's?

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

I am getting 33% slip for 23mph at 3800rpm from a prop calculator. What is the mph at the 5000rpm's?

At 5000 rpm I get around 35mph, I think that it could be more, if there were beter sea conditions.

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Why do you think that I have so much slip?? Because of twin drives? Or are props bad? I tested that with old used props. what is the difference betwean 14 1/2 or 14 1/4 props?

 

[hwsiii]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Gasper, I received a notification that you had sent me a private message.

H

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Gasper, I received a notification that you had sent me a private message.

H

Yes, I want to ask you to read this tread and try to help me with this problem.

Thank you

 

[hwsiii]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Gasper, I will have many questions that i will need answers to in order to possibly help you get the right props for your boat.

The first ones are exactly which model 3L Volvo engines you have and horsepower, as well as the RPM range for those motors and the real gear ratio of your outdrives, as when I do any analysis I start off with mathematical formulas and progressively move towards the art, LOL.

Also you mentioned that you might change the rotation of the engines so they both turn right hand, is this actually what you did, because this can create possible problems with prop wash and side walking as well as other problems.

H

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Gasper, I will have many questions that i will need answers to in order to possibly help you get the right props for your boat.

The first ones are exactly which model 3L Volvo engines you have and horsepower, as well as the RPM range for those motors and the real gear ratio of your outdrives, as when I do any analysis I start off with mathematical formulas and progressively move towards the art, LOL.

Also you mentioned that you might change the rotation of the engines so they both turn right hand, is this actually what you did, because this can create possible problems with prop wash and side walking as well as other problems.

H

The engines are Volvo penta 3.0 GS 135hp.
WOt RPM should be 4600rpm, and planing around 3200rpm
The gear ratio is 2.18 the drive is SX-M cobra

I change the drive rotation only to test it with those 14 1/4 x 21 props, coz I only get two rihgt hand. As I said this was only for test, now I want to buy left and right hand props.

Thank you again for help

 

[hwsiii]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Gasper, will you please send me your telephone number to my email hwsiii@yahoo.com so I can call you and ask some of the questions I need to know the answers to.

H

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

rely no one to help me??

 

[jestor68]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

You need larger diameter props to solve your slippage problem and provide overall better performance.

Since the 14.25 X 21's were getting you into the ball park, I recommend a pair of Solas Rubex 15.75 X 21" pitch. They are available in both right and left rotation. They are also available in 15.3 X 22", but I do not think you will need to go that high.

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

You need larger diameter props to solve your slippage problem and provide overall better performance.

Since the 14.25 X 21's were getting you into the ball park, I recommend a pair of Solas Rubex 15.75 X 21" pitch. They are available in both right and left rotation. They are also available in 15.3 X 22", but I do not think you will need to go that high.

Thank you for answer.

Now I see that the biggest problem will be find that propellers. I can't believe that this is such big problem in europe.

 

[jestor68]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

The props I am referring to are Solas Amita 3-E Plus. They are 15.3 X 21 pitch aluminum props.

Part numbers are: 8611-153-21(right hand); 8612-153-21(left hand).

iboats shows them in their prop section for $106.19(plus shipping). I don't know if iboats ships internationally.

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

The props I am referring to are Solas Amita 3-E Plus. They are 15.3 X 21 pitch aluminum props.

Part numbers are: 8611-153-21(right hand); 8612-153-21(left hand).

iboats shows them in their prop section for $106.19(plus shipping). I don't know if iboats ships internationally.

I look that props, and they ship internationally, but it takes 9 business day, so this could be 14 days plus one week our customs, to charge me all duties... And we go on vacations next week.
I rely hope, that this props will not spoil our vacations.

 

[gbratk]

Re: Twin Volvo 3.0 HIGH plane RMP Problems

Is anyone buying something from I boats? I pay for props 4 days ago and I didn't get any answer yet, if its shipped or something... I also send him mail, and ask when can I expect that props will be shipped, but no answer... I'm rely nervous that this props will destroy my season...


The props were shipped today. We'll see how long it takes to get it.