CAT 3126 420 to Cummins 6CTA 430

[Bill Desmarais]

Posting this for a guy on down east boat forum.
I’ve asked him to join……”hell it’s free” !!!!!

“hey bill I know your a cummins guy and are very knowledgeable in this are I’m thinking for down the road I have a cat 3126B 420hp now with a td2.5:1 gear if I put in a recon 6cta 430hp could I use the same gear the cat turns 2800 wot the cummins 2600 wot”

The boat is a beautiful 36 H&H down east lobster cruiser/fishing boat.

28X26 LH wheel right now. Can take up to a 30″ prop.

http://www.hhmarineinc.com/models/osmond36.htm

Owner would like to stay with the TD 2.5:1 gear in the boat now.

Tony ?

Topic

[Tony Athens]

Propped right, the 6CTA 8.3 will turn at least 2750 and can run all day at 2400 RPM.. If you are working the motor super easy, just add 1-2″ of pitch to get the R’s down to 2200 or so to get your happy vessel speed.

Don’t confuse MINIMUM rated RPM or test cell data with how this engine really likes to be propped in the field under real ocean/working conditions. .

Tony

1 user thanked author for this post.

Bill Desmarais

[Sean Quintal]

Yes that’s what I was getting at my motor now is a 2800 rpm engine I run it 400 off the top that’s it’s happy spot but if the cummins is a 2600 rpm motor and I need to turn her up the same rpm 2400 rpm that would only be 200 off the top isn’t that pushing it a little hard to get the same speed I’m probably better going with a recon qsc 550 hp more rpm range could I still run a 2.5:1 gear or would I have to get a new gear and prop for best results I understand with more hp to utilize I can move more water more pitch or surface area what would be the ideal gear and prop thanks

[Bill Desmarais]

Tony Athens wrote:

I am not sure exactly what you are asking but if you put in a 430 C and use the same gear & prop, the 430 will run very easy and probably will make over 2700 RPM with “no sweat”..

The vessel speed will be exactly the same RPM to RPM , as remember, “the prop moves the boat, the engine just turns it” (in so many words)..

If the guy wants more performance, do a 1st class repower, do not change the prop, put 50 hours on the vessel, and then we’ll look at the numbers and compare to the Cummins specs , look at all, and go from there.

Tony

Tony,

Sean says he cruises the CAT @ 2400 rpms…..can he safely cruise the 6CTA @ 2400 rpms day in day out if verified propped to 2700 fully loaded ???

[Sean Quintal]

Hey I’m the owner of the H&H clean bottom when I put first go in I cruise at 16-17 at 2400 rpm

[Bill Desmarais]

Thanks Tony,
I’ll ask him what he cruises the CAT for rpms

[Tony Athens]

I am not sure exactly what you are asking but if you put in a 430 C and use the same gear & prop, the 430 will run very easy and probably will make over 2700 RPM with “no sweat”..

The vessel speed will be exactly the same RPM to RPM , as remember, “the prop moves the boat, the engine just turns it” (in so many words)..

If the guy wants more performance, do a 1st class repower, do not change the prop, put 50 hours on the vessel, and then we’ll look at the numbers and compare to the Cummins specs , look at all, and go from there.

Tony

[Author]

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