shaft log and shaft diameter

[Darren Kinvig]

I have a question about shaft diameter VS shaft log diameter. I am doing a re-power. I need to increase the shaft diameter from 1 3/8 to 1 1/2 diameter. I would like to keep the same shaft log. The inside diameter of the shaft log is 1 15/16 That leaves a bit more than 3/16 clearance around the 1 1/2 diameter prop shaft. How crucial is the clearance between prop shaft and shaft log. Is this enough clearance?

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[Darren Kinvig]

Shaft log clearance.

Thanks for the reply. I am starting with nothing but the shaft tube/log in the boat. The strut will need to be replaced. The prop shaft that came with the boat was an 1 3/8 . I will go to an 1 1/2 shaft diameter. I was hoping not to replace the shaft log. My first time doing an inboard/v drive set up. So the extra clearance sounds like a good idea. Your shaft was so miss aligned that it was wearing at the shaft log/tube itself. Allot to learn. Thanks again for your reply. Some helpful information in there.

[pwrobert]

Shaft log clearance

Should work ok but when you have minimal clearance it becomes very important to align struts and engine so the shaft is perfectly centered at both ends of the tube. May require resetting the strut in many cases.
If clearance is not same at both ends of tube your other option is to reset the tube itself. If that is the case then might as well put in the newer shaft tube. Maybe 2” or 2-1/2” ID.

IF you go the new route get custom spacers made it of plastic to hold shaft dead centers d glass it in place. I did both of mine back in 2013.

I ran the boat for many years with the OEM smaller tubes like you’d with 1-1/2“ shaft inside and undetected the shafts began to wear the tubes and had a near disaster with leak. Luckily yard got me right out and I was good. Had to pull two fuel tanks to get at tubes and decided to replace both even though only one was worn through.

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