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Thread: Cutting & Resplining Driveshaft

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    Default Cutting & Resplining Driveshaft

    I recently bought a 30hp Yamaha with a bum lower. It has a pretty big crack with a questionable looking repair weld so I think I'm gonna shop around for a lower. Having trouble finding a 25/30 lower but there are a lot of 40's available. Have read elsewhere they bolt up but require the driveshaft to be cut down slightly (3/8-1/2") and splines extended down same length. I'm no machinist so I'm wondering if this is something most automotive type machine shops can handle or if its a job for a more specialized place? Curious on what the cost may be as well for a trim and spline extension or a ~5" removal and total respline to make it a short shaft?

    And somewhat on subject, I have both a 30 long and short driveshaft and could just swap either out for the 40 one....if they will fit.

    Anyone have any thoughts?

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    Team Member hydrospeed77's Avatar
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    I had success finding a machine shop that specializes in gears and shafts. They shortened a couple drive shafts and matched the splines to the original. I did provide a spare crank to help them to match clearances. They happened to have the hob needed for the splines.

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    Quote Originally Posted by hydrospeed77 View Post
    I had success finding a machine shop that specializes in gears and shafts. They shortened a couple drive shafts and matched the splines to the original. I did provide a spare crank to help them to match clearances. They happened to have the hob needed for the splines.
    Thanks for the reply! What was the cost if you don't mind me asking?

    I found a replacement lower last week so I'm good on that front now. But, I'd still like to pick up a spare and try to grab a 40/50 lower for that as they are supposedly a little beefier.

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    Team Member hydrospeed77's Avatar
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    Quote Originally Posted by wmk0002 View Post
    Thanks for the reply! What was the cost if you don't mind me asking?
    I had brought 2 shafts in with me to get a quote, and it was approx 1.5 or 2 hours of shop time for both (approx $95 CAD per shaft). Turns out, for a single driveshaft, that's about half the price of an inexpensive aftermarket shaft on ebay. But I happen to have the extra long driveshafts already. If I didn't already have a driveshaft to modify, it would have been less expensive to order a cheap ebay short shaft.. Although, I've only had one report of the quality of those.. But it was positive.

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    Quote Originally Posted by hydrospeed77 View Post
    I had brought 2 shafts in with me to get a quote, and it was approx 1.5 or 2 hours of shop time for both (approx $95 CAD per shaft). Turns out, for a single driveshaft, that's about half the price of an inexpensive aftermarket shaft on ebay. But I happen to have the extra long driveshafts already. If I didn't already have a driveshaft to modify, it would have been less expensive to order a cheap ebay short shaft.. Although, I've only had one report of the quality of those.. But it was positive.
    Thanks. That's about what I would expect. I actually have a long and short driveshaft from a 25/30 so I could do a shaft swap, however, I haven't been able to find any info on if the 25/30 shaft actually fits in the 40/50 lower. I'm also reluctant to replace shafts as I would have to re-shim it. I don't think the job would be very hard it just requires a number of special tools, none of which I have.

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    Team Member hydrospeed77's Avatar
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    Sometimes you can get an indication from comparing the parts catalogs for both motors. Looks like the driveshaft top bearing is shared as well as the shims in that location, but the lower bearing near the pinion is different. If bearing and shim parts numbers were the same all round, then I'd say chances are good.. But in this case looks like maybe not. You'd have to compare the lower bearings and also the length between the two driveshaft bearings. And also a major one: the splines for the pinion gear.

    And yes, at least a couple special tools.
    Last edited by hydrospeed77; 08-15-2019 at 08:24 AM. Reason: typo

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    Thanks. That makes sense. Maybe I will get a chance to verify for myself soon.

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