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Old 05-20-2023, 06:59 PM
Grappler Grappler is offline
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Moving a reducing gear to a direct drive A4

The A4 in my Columbia 36 has been getting very hard to start, and running poorly, with low compression (68-80 psi). It has the reduction gear housing.

A friend who rebuilds marine diesels has an A4 that he acquired recently that appears to be a newer model than mine. It starts readily, runs, and has 90 psi compression on all cylinders.

I thought it could be drop-in compatible replacement for my A4 till I discovered that it doesn't have the reduction gear housing. So it's about 5" shorter than my A4. I thought this might be ok if I just got a longer prop shaft, but then realized I'd also need a different prop. And now I see from the A4 manual and from one of the posts on the forum that the height of the output shaft is 1.042" higher on the direct drive A4, so if I use it, I'll have to lower the engine by that amount to line up with my prop shaft. This would be very difficult. I'd have to remove material from the existing fiberglass engine supports.

So now I'm thinking I might be better off moving the reduction gear from my old A4 to the newer A4.

Can anyone point me to some hints/advice/instructions for doing this? I haven't found much in this forum, but see that some people transplant the reduction gear with the reversing gear.

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reduction gear, reversing gear

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