Amarc Diesel Gearset Woes

[lotec]

I have a few days off for Christmas so I finally got back to my long-term 1960 Amarc 9.25hp diesel outboard project. Last summer, after an exhaustive search, I found an impeller that would work and went to test it using a drill, an old Scott Atwater trick. (Hate to get the motor all back together to find it doesn’t pump!) At that time I noticed a "clicking sound" when in forward gear but didn’t have a chance to investigate.

BAD NEWS!!! I opened up the gear case today to find 3 teeth broken off the forward gear. The good news is I found all 3 pieces and they were totally intact, I’m not sure how that is possible since they should have been ground up like pepper in there if the motor was run with them broken. The former owner told me the motor took a major fall, but I don’t see how this could have broken from that – especially with 2 broken on one side and the other 180 degrees out. The prop wasn’t dinged up so I can only guess it was from jamming into gear at high RPM? I guess the cause isn’t as much of a concern as what to do to fix it, I don’t think a hardened gear can be welded? The forward and reverse gears are totally different so they can’t be swapped.

The shift system is similar to the type Scott and West Bend used so I’m hoping Amarc purchased the gears from them. I’ve pretty much ruled out Scott since they only used the gears on the propshaft up through 1953 on the 7.5hp+ motors and, based on the manuals, they are all 21 tooth. The couple of photos I have of my 6hp and 7.5hp West Bend gears only show 3 ramps for the clutch dog, not sure about the larger motors. Below are 3 photos, does anyone have any thoughts or recognize this gear from another motor?

Amarc 10 Gearset

Closeup

Gear dimensions

[Mumbles]

Hoo boy, I think you have your work cut out here. Hopefully you can find a set or a close match which will work with a bit of machining. The number of ramps shouldn’t be as important as the diameter of a replacement pinion to keep the geometry in order.

I know guys have replaced RBM gears with ones from McMaster-Carr after machining them to fit but the ramps on yours present a problem unless you want it to be a direct drive. It’s quite possible Amarc sourced these out from somewhere instead of making their own so I’m confident that something, somewhere, will work for you!

To try and help you out, I’ll dig out my Amarc gears and hold them in my hand to see if I can get a brainwave!

http://www.mcmaster.com/#catalog/121/1107/=10bvh77

[billw]

Those gears and clutch look very, VERY much like Mercury…..Mark 20, 25, 30,55….probably more. Give me a side view of the gears. I don’t have much in the way of good 20/25/30 gears but I have a pretty nice set of Mark 55s…..I mean, I know that would be too easy but they look SO much like Mercury gears that it’s worth some leg work to check out. Is that diameter to the outer tips of the the teeth?

Long live American manufacturing!

[lotec]

Thanks for the link Jim – I’m clinging to Bill’s thoughts like a drowning man to a life jacket! 🙄 As most know, I’m not much of a Merc-man so I didn’t even think about that as the source. Plus, I’d never dream EKC would sell gears to a competitor, even one as lowly and nonthreatening as Amarc….

Here are some additional shots and dimensions, Bill let me know what else would be helpful. (I also emailed you them directly) If you think this is similar I’m sure I can round up a set of Mark 20, 25 or 55 gears from someone.

Addl dimensions

Side-View

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