Twin Disc or ZF gear in new repower?

[Bill Desmarais]

Hello Tony,

Kicking around a repower of a used lobster boat.

Existing power plant is a 99 Deere 6068 225 hp rated @ 2600.

Gear tag is unreadable but I believe is a Twin Disk 2:1, 1.75″ shaft swinging a 24X24 four blade.

Proposed repower is a QSB 5.9 480. The gear replacement is up for discussion.

I prefer to keep the engine angle the same, so I figure maybe a TD5075SC or 5075A 2.88:1 “or some other gear” swinging a 26X? prop.

Larry @ Accutech dialed in a 2.5:1 gear with a 26X30 ??

I won’t be using anywhere near the hp of the 480.

Appreciate ant insight,

Bill D

Topic

[Tony Athens]

Bill,

You need to ID the gear you have now if you want to select something that will actually FIT the boat and clear the hull.. Most all of these hulls set the shaft in such a way as you have do some homework to see what will fit and clear the bilge roll/hull.

Look at the picture– Get your camera behind the gear –Lay the camera on the shaft and shoot forward.. A good picture from that angle will let me ID what you have now.. Try and also get a shot showing the clearance under the gear.

From what I see, a Twin Disc MG5057SC or MG5075A would not work at all..It’s a massive gear compared to what you have now in there.. Plus, fitting it to a QSB 5.9– Not something for the timid at all. .

As to a 26″ prop on a 1.75″ shaft– NEVER in my book would I even consider going there. Larry should know better that that.

Tony

[Author]

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