Alpha One Lower Unit

[JohnJones427]

I have a chunk missing on the lower unit where the hydrofoil fin thingy-ma-jiggy bolts on. Can I weld it or braze it with torch and rod while it’s on the boat? Obviously it should be removed, but I don’t know what I’m doing enough to tear the lower unit apart safely and quickly. I do know how to weld, braze, solder though.

 

[Dieter]

I have a chunk missing on the lower unit where the hydrofoil fin thingy-ma-jiggy bolts on. Can I weld it or braze it with torch and rod while it’s on the boat? Obviously it should be removed, but I don’t know what I’m doing enough to tear the lower unit apart safely and quickly. I do know how to weld, braze, solder though.

Very common for welding shops or prop shops to tig these back togther on the boat with out disassembly.

Ditch the hydrofoil. That’s why it broke.

 

[wndsofchng06]

Very common for welding shops or prop shops to tig these back togther on the boat with out disassembly.

Ditch the hydrofoil. That’s why it broke.

I had mine tigged back on. How does the hydrofoil cause breakage?

 

[makomark]

the casting breaks as it isn't thick enough to handle the load the 'fin' puts on it when the boat is moving...

 

[wndsofchng06]

the casting breaks as it isn't thick enough to handle the load the 'fin' puts on it when the boat is moving...

Interesting! Thanks. I would have never thought of that

 

[Dieter]

Interesting! Thanks. I would have never thought of that

Mako has it. The cav plate is not made for that kind of load. The hydrofoil manufacturers leave that out of the sales pitch.

I had a cheap plastic two piece (two bolt holes on each side of the plate) foil on my alpha gen one years ago. It definitely helped planning until it snapped the cav plate at the bolt holes...

I found the same performance benefits - hole shot and stern lift going to an inexpensive aluminum Michigan Votex 4 blade prop

 

[Rowenshock]

I

Is this the hydrofoil you are refering to. I was out last saturday in deep water when i heard a bang while doing about 30. When i looked this piece was gone. Are you suggesting its not strong enough. I assumed something like a log under the water went in there and snapped it after being driven by the prop. I presume there is nothing like a skeg guard that i could just bolt on.

 

[Dieter]

I View attachment 32547

Is this the hydrofoil you are refering to. I was out last saturday in deep water when i heard a bang while doing about 30. When i looked this piece was gone. Are you suggesting its not strong enough. I assumed something like a log under the water went in there and snapped it after being driven by the prop. I presume there is nothing like a skeg guard that i could just bolt on.

no that is the cavitation plate . the fin is something like this that bolts to the cav plate and promises some performance improvements... but they put stress on the cav plate and can bust them

Doel-Fin Stabilizer Fin, black - SKU 440

Doel-Fin is the original hydrofoil developed by an aeronautical engineer to improve overall performance on all boats with outboard motors or outdrive units. Molded in two pieces of guaranteed unbreakable, high-strength plastic, each foil is designed to flex independently to absorb shock...

www.davisinstruments.com

there is no skeg plate to bolt on - a decent welding shop or propeller repair shop can fix like this

Skeg and Cavitation Plate Repair | PropMD - Propeller Sales & Repair

Chipped up your skeg recently, or even break the whole thing off? At Prop MD we can repair your partially, majorly, or even entirely missing skeg.

propmd.com

 

[Kwik2ce]

I View attachment 32547

Is this the hydrofoil you are refering to. I was out last saturday in deep water when i heard a bang while doing about 30. When i looked this piece was gone. Are you suggesting its not strong enough. I assumed something like a log under the water went in there and snapped it after being driven by the prop. I presume there is nothing like a skeg guard that i could just bolt on.

 

[Kwik2ce]

This must be common, and we should be compensated. Would like to know what you ended up doing..This just happened 4th of July weekend ...1st ride down the river for the season..Don't know how to post pictures, but mine broke in excat same spot!

 

[Rowenshock]

This must be common, and we should be compensated. Would like to know what you ended up doing..This just happened 4th of July weekend ...1st ride down the river for the season..Don't know how to post pictures, but mine broke in excat same spot!

Oh bad luck.... I ended up getting a new aluminium piece welded to it. Not an exact match but good enough.It was a relatively easy job for any work shop. Getting the boat to them proved the most difficult issue.
Out of interest two months ago my gimble bearing went and i suspect the vibration from this over a period didnt help with this.. I'm running much better now.

 

[Dieter]

This must be common, and we should be compensated. Would like to know what you ended up doing..This just happened 4th of July weekend ...1st ride down the river for the season..Don't know how to post pictures, but mine broke in excat same spot!

I ran it a couple seasons didn't notice much difference but did start to see some cavitation burn on the props. Eventually I JB welded a strip of aluminum to the underside, but my missing piece was smaller.

While that worked- This was a pretty old boat at the time so I was being cheap... If you are going to keep it a welding whop or prop shop can weld in a piece, which is a very common repair. If you find the right place you can bring it on the trailer to fix. no need to pull the drive.