Gear ratio question on an engine change 30 CB

[BillD]

I have an owner who asked me a question. I figured I put it out here.

He has a 30 South Shore with a 230 Isuzu. He has a "new" 6BT 230 (yes a 230) Cummins he's wants to install over the winter.
Right now with the Isuzu he's spinning a 22X22 square prop with a 2:1 gear and a 1.5" shaft.

Some guys, maybe Cummins, mentioned he may want to consider a 1.75:1 gear with the "new" Cummins power and maybe pick up some "pitch".

IMO it's not worth the hassle or cost to drop from a 2 to 1.75 gear.

Not sure if he runs a cage or not on the 30 CB

What do you guys think ????

Thanks, Bill D

 

[steveinak]

I'm no expert but i'm running a over square wheel (24x26) and all seems well and i agree with you why go to all the trouble and expense when maybe just playing with the prop will do the same ??

 

[BillD]

I have an owner who asked me a question. I figured I put it out here.

He has a 30 South Shore with a 230 Isuzu. He has a "new" 6BT 230 (yes a 230) Cummins he's wants to install over the winter.
Right now with the Isuzu he's spinning a 22X22 square prop with a 2:1 gear and a 1.5" shaft.

Some guys, maybe Cummins, mentioned he may want to consider a 1.75:1 gear with the "new" Cummins power and maybe pick up some "pitch".

IMO it's not worth the hassle or cost to drop from a 2 to 1.75 gear.

Not sure if he runs a cage or not on the 30 CB

What do you guys think ????

Thanks, Bill D

I'm no expert but i'm running a over square wheel (24x26) and all seems well and i agree with you why go to all the trouble and expense when maybe just playing with the prop will do the same ??

That's my thought. He's talking 30 hp increase, why mess with everything.

 

[djmarchand]

The Cummins makes its 230 hp at 2,600 rpm. What rpm does the Isuzu make its 230 hp at? Until you answer that question, every one is shooting in the dark.

David

 

[captainlarry84]

The Cummins makes its 230 hp at 2,600 rpm. What rpm does the Isuzu make its 230 hp at? Until you answer that question, every one is shooting in the dark.

David

Agreed this is the magic question we need the RPMs of both motors.

 

[BillD]

Has to be the Isuzu...226 SAE hp, 2600 or 2700 depending on rating

Only one close to 230 HP

http://boatdiesel.com/Engines/Engin...7654A864BA9494565A928CAA66464AB8B2469A98AE641

 

[WoundUpMarine]

Pretty sure i know who your talking about, he has the 6bg-1t, same as mine, think its a 2700 rpm engine.

 

[BillD]

Pretty sure i know who your talking about, he has the 6bg-1t, same as mine, think its a 2700 rpm engine.

That's what I figured, 2700.
Me, I'd stay with the same gear, 2:1, keep it easier and less costly for the engine change.

 

[WoundUpMarine]

Wish i had a 2:1 on my engine, be nice to swing that bigger wheel.

 

[captainlarry84]

RPMs are almost the same therefore I would stick with the 2:0 gearing.

 

[lobstercatcher]

Wish i had a 2:1 on my engine, be nice to swing that bigger wheel.

What do you have for a gear ratio?

 

[WoundUpMarine]

1.5:1 spinning a 20x18, (i think on the wheel size maybe 20x19)