Propping a 38 libby

[Spear-it]

I have a 26 square prop on my Duffy 35. I am running a 6cta 430 hp with 2 to 1 gear as well. She weighs in around 19000 #.
My high RPM is a 2630 . About perfect.
Maybe you can use this info as a benchmark.
Great job on the boat!

Thank you Roger that's super helpful! My weight is about the same as yours. Sounds like we are close with our numbers .
Thank you on the boat work compliment!

 

[Fella]

I have a 38’ Libby that is lighter than your boat. Has an open house, lobster style with only a v-birth down below. 300HP JD twin disc 2:1 with a 26x29 4 blade/no cup. I do 16kts at 1900.

 

[Spear-it]

I have a 38’ Libby that is lighter than your boat. Has an open house, lobster style with only a v-birth down below. 300HP JD twin disc 2:1 with a 26x29 4 blade/no cup. I do 16kts at 1900.

Dam 26x29 that would indicate to me that I will blow right through a 26x26. I've never gotten a boat propped right out of the gate but I'd rather be under propped than over .

How do you like the libby hull? I haven't actually run one but I have heard nothing but good things . I'm excited to get this boat done and splased .

 

[traditions]

I have a 26 square on my 38 Holland , 430 Cummins, 2 to 1 gear, turns 2600 on mechanical tach. Best to see if you could borrow a confirmed wheel from some one to get a baseline before buying one, and having to repitch.As long as you know where you are starting from. You are looking at probably 500 bucks to do any bending. Just my opinion.

 

[Spear-it]

I have a 26 square on my 38 Holland , 430 Cummins, 2 to 1 gear, turns 2600 on mechanical tach. Best to see if you could borrow a confirmed wheel from some one to get a baseline before buying one, and having to repitch.As long as you know where you are starting from. You are looking at probably 500 bucks to do any bending. Just my opinion.

I agree with your opinion, however, my
issue is when I splash this boat I'll be running daily with in a week. I need to be close or a little under propped or ill be changing this thing at night between Charters. You dont worry about the 2600 rpms being a little low and lugging the motor ? I was going to go 26 square with light cup but now I'm thinking I'll go with no cup. I could get through the season under propped and loosing a little speed.

 

[Fella]

Dam 26x29 that would indicate to me that I will blow right through a 26x26. I've never gotten a boat propped right out of the gate but I'd rather be under propped than over .

How do you like the libby hull? I haven't actually run one but I have heard nothing but good things . I'm excited to get this boat done and splased .

Yes, were you from? There’s prop shops that will take your boats info and run it in their program.

I love my Libby. I’ve wanted one for years and one finally came along perfect for me a few years ago. Commercial lobster with it. Wide, fast, solid hull.

 

[Roger H]

I agree with your opinion, however, my
issue is when I splash this boat I'll be running daily with in a week. I need to be close or a little under propped or ill be changing this thing at night between Charters. You dont worry about the 2600 rpms being a little low and lugging the motor ? I was going to go 26 square with light cup but now I'm thinking I'll go with no cup. I could get through the season under propped and loosing a little speed.

I agree with Tony Athens from Seaboard marine. " There is no such thing as an under propped boat"

 

[Spear-it]

Yes, were you from? There’s prop shops that will take your boats info and run it in their program.

I love my Libby. I’ve wanted one for years and one finally came along perfect for me a few years ago. Commercial lobster with it. Wide, fast, solid hull.

Awesome! Can't wait to run her . She should move pretty good with the 430.

 

[traditions]

I agree with your opinion, however, my
issue is when I splash this boat I'll be running daily with in a week. I need to be close or a little under propped or ill be changing this thing at night between Charters. You dont worry about the 2600 rpms being a little low and lugging the motor ? I was going to go 26 square with light cup but now I'm thinking I'll go with no cup. I could get through the season under propped and loosing a little speed.

Supposed to turn 2600. Runs 2600 loaded. I never photo tached it. If it was turning 2500, I would have put the photo on it. I bought the boat used , and that is the wheel that was on her. I have added a lot of weight, and she still turns 2600

 

[Spear-it]

Supposed to turn 2600. Runs 2600 loaded. I never photo tached it. If it was turning 2500, I would have put the photo on it. I bought the boat used , and that is the wheel that was on her. I have added a lot of weight, and she still turns 2600

Got ya . I think cummins calls for 2700 to 2830 loaded. Is that correct?

 

[Roger H]

Got ya . I think cummins calls for 2700 to 2830 loaded. Is that correct?

I think it's 2800 to 2900 unloaded. High Idle.

 

[Red At Night Series]

QSL9 405 HP 2100 max rpm
QSC8.3 depends on duty rating. Recreational is 2600/493 hp and 3000/543 and 593. Commercial and light duty is 2600/493 hp and below 2800/530hp and above.
According to the Cummins website via google search...... just saying.

 

[Spear-it]

I think it's 2800 to 2900 unloaded. High Idle.

that sounds right. I'm told the 8.3 6cta motor does not do well when overloaded .

 

[Spear-it]

QSL9 405 HP 2100 max rpm
QSC8.3 depends on duty rating. Recreational is 2600/493 hp and 3000/543 and 593. Commercial and light duty is 2600/493 hp and below 2800/530hp and above.
According to the Cummins website via google search...... just saying.

2600 to 2650 on the 430 8.3 6cta seems to be the max RPMs I am looking for. Does that sound right?

 

[Jjammer]

2600 to 2650 on the 430 8.3 6cta seems to be the max RPMs I am looking for. Does that sound right?

Propping a Cummins Mechanical Diesel Engine

www.sbmar.com

 

[Red At Night Series]

2600 to 2650 on the 430 8.3 6cta seems to be the max RPMs I am looking for. Does that sound right?

 

[Spear-it]

View attachment 179974

thank you

 

[Spear-it]

http://[URL]https://www.sbmar.com/articles/propping-cummins-mechanical-diesel-engine/

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Great info thank you .

 

[traditions]

Got ya . I think cummins calls for 2700 to 2830 loaded. Is that correct?

B series maybe. C series 430 2600

 

[Spear-it]

B series maybe. C series 430 2600

Thank you Got the 2600 rpms .

Anyone else with experience propping the 38 libby?