Yamaha cavitation plate repair

w2much

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I have not seen this question asked so either it is not a good question for this forum or or or just not a good question . My plate above the prop has broken off and I am in the process of repairing it. I would prefer a painless (pay less) aproach . Paint has been removed and the metal has been prepped . The replacement parts have cut to fit . Instead of just fitting the missing peice in place I cut an entirely new plate , one peice to fit over the entire original . Of course there is a slot so that I can slide it into place . I did this because I am assuming that the new plate sandwiched with the old plate will lend to support each other each llending integrity to the other. Instead of the cavitation plate being about 1/8" thick it would now be close to 1/4" thick . This new sandwiched plate would be painted to finish . I know welding is the preferred method for attachment but here is my question. Might Loctite 5200 work in between the plates and up against the lower unit itself to hold it in plate . Holes drilled into the new peice would allow the 5200 to come through and form a better bond and also assure that a there is full coverage of ashesive contact throughout the sandwiched area. OK so without all the detail is this a feasable repair . Is this the wrong forum . Am I being so tight that I am depriving my brain of oxygen.
 

alldodge

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5200 is great but not that great, it might hold for a while, but not that long

Sandwiched plates will hold but may also cause cavitation because of the edge on the lower side. The water flowing under it may cause bubbles and then you just lost some slip
 

w2much

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Great answer . I thought on the bubbles and cavitation which is why I decided to put the plate on top instead of under the broken original . i agree with your answer . What about using JD Weld epoxy inplace of the 5200 ?
 

alldodge

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What about using JD Weld epoxy inplace of the 5200 ?
Same answer, JB is good stuff but will not hold up under a torque load. The Cav plate riding straight will get vibration, but in a turn there will be more loading and vibration and IMO don't see how it will last.

As always this is just my opinion, no direct test knowledge
 

Chris1956

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If you do not want to have it welded, at least use pop rivets. They come in larger, stronger sizes like 1/4".
 

cyclops222

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ONLY by a very experienced Marine Aluminum housing welder. Only 1 in my boating area.
Steel & Iron people need not attempt the repair. Been there with them. (n)
 

w2much

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as Cyclops says . which is why I moved to think of epoxies rather than take the time and effort to find a good aluminum welder.
 

JimS123

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as Cyclops says . which is why I moved to think of epoxies rather than take the time and effort to find a good aluminum welder.
I see, you don't have the time now, but have the time to do it over.

No epoxy has the strength of aluminum or an aluminum weld.
 

chrisgt

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Sep 23, 2024
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Many yards have welders they use, call around and see if they can reference you to a welder; it might be cheaper than you expect.

Also I don't know what you were planning to use as replacement material, but you DO NOT want 6061 or 6063, it will corrode in marine use and if it's welded to cast aluminum it becomes brittle at the weld and tends to crack off if impacted.

You want to tig weld a piece of cast iron with 5356 rod to replace the missing material. I just did this repair to a skeg on one of my outboards and it came out great. The whole job took me an hour or less and i'm just a youtube certified hobby welder, a pro could probably do this repair for $100.
1736171944247.png
 

Mc Tool

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Aug 7, 2024
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A pic would be great
Can you not just fit one of them bolt on cavitation plate extention fins ?
I have a " Permatrim " on my Honda
maxresdefault.jpg
or am I missing something ( thats not my boat .... just an image off the net )
 
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