Volvo 125 HP prop question

[patskialta]

Hi all,
I am a newbi here and just bought a 1986 19 foot Glastron CX19D cuddy at the end of last season.The boat came with 2 props one is a 21pitch 14"all beaten up the other is a Michigan 19 pitch 15" I brought both to have them repaird. The 14" was fixed within a day but then I was told that before spending the money on the 15" Michigan to find out if my boat can handle it, the mechanic thinks it is to much prop for such a boat.
My question is can my boat handle the 15" and would it be better for towing than the smaller prop or is the 14" the max I can put on the boat.

I Thank you

Pasquale

 

[jestor68]

Re: Volvo 125 HP prop question

Think of an inch of diameter as roughly equivalent to an inch of pitch; so the 15 X 19 would not operate much differently than the 14 X 21 pitch prop ( like only an inch of pitch difference).

Assuming your gear ratio is about 2.0(2.15?), that favors the larger diameter prop.

Depending on what drive you have(270, 280?), Volvo makes props in 14", 15", and 16" diameters. The larger diameter/less pitch would provide the best thrust/pulling power.

 

[steelespike]

Re: Volvo 125 HP prop question

I'm thinking both are too much prop for a 19 ft cuddy.
If the prop doesn't cost ridiculous you need a prop to make a test run lightly loaded to get a base line rpm and gps speed.
By the way give your prop size diameter X pitch. 15 X 19.
I think a 17 may be closer to what you need but you should get a base line before any decision.

 

[jestor68]

Re: Volvo 125 HP prop question

I recommend you visit the Volvo Penta web site; where you can open and print (in the engine data base section) owner manual and update bulletins covering your 1986 AQ 131(120 hp) engine and 275D drive.

 

[patskialta]

Re: Volvo 125 HP prop question

Thank you for your response, I finally tried the boat with my 14X21 and it was not good it took 5min to reach 4000 rpm (in choppy waters with 4 on board) where it toped out. I think this coming weekend I will try the 15X17 prop

Thanks once again

 

[steelespike]

Re: Volvo 125 HP prop question

I thought it was a 15 X 19 prop.
While it's obvious the 21 is too much prop if you had done a lightly loaded test run with the wot rpm and gps speed
We probably could tell you what prop you need.
When you do a test run with a load the only thing we can tell is what prop will likely work better with that load.
It could result in over revving when lightly loaded.
We can't tell if your setup is right, motor healthy etc.

 

[patskialta]

Re: Volvo 125 HP prop question

Hi,
I found a 14X17 prop that a local welder made me try out. I tried it lightly loaded and took off no problem add hit a mat of 3900RPM and a GPS speed of 42KMH (aprox 26 MPH). I guess that is ok as soon as I loaded up with wife, 2 kids (aprox 378pounds) and cooler the boad preformed no diffrent than when it had the 14X21prop took about 10 min to reach 3900RPM and same speed. And when the water was a little choppy it maxed at 3000RPM and 14KMH (9MPH).
Do I need to go bigger like 15X17 or..
The motor is a Volvo Penta AQ125 A

Thanks
Pasquale