How to Repair Cavitaion Plate

[blklab]

I just bought a New Johnson 25 and Broke part of the Cavitation plate off. I do not remember hitting anything we have had the motor in the water 4 times. What are some methods of fixing this plate.

 

[WillyBWright]

Re: How to Repair Cavitaion Plate

I have had our skeg welder repair antiventilation plates as well. But yours is rather thin. I don't know.

 

[dolluper]

Re: How to Repair Cavitaion Plate

there is a product called NUSTEEL it's like epoxsy with metal fibers ,cut a peice of cardboard cut to shape of break and tape underneath apply a thin coat let sit then grind another coat grind and so on just make sure starting surface is ground down to bare metal first appox 1/2 to 1 inch around break It works real good done it many times witholds lots of water pressure

 

[frappazza]

Re: How to Repair Cavitaion Plate

I'm an internatinal welding engeneer and obviously i suggest you to weld a new alluminium plate to replace the part you lost.<br />The most relyable welding process for that kind of material and thikness is a tig welding of both faces without grinding for improved strenght.

 

[walleyehed]

Re: How to Repair Cavitaion Plate

I've had real good luck with MarineTex..tape a piece of cardboard or balsa wood on th bottom side to prep a flat surface, clean the break with M.E.K. or simular NON-oily solvent, put'er on and sand down excess when dry.

 

[blklab]

Re: How to Repair Cavitaion Plate

francesco How difficult is it to weld the Cavitation plate. would Ineed to take the Lower Unit off or can it be done attached. I relize the heat would be an issue on the internal parts of the Lower Unit.<br /><br />Ed

 

[G DANE]

Re: How to Repair Cavitaion Plate

As aluminium is brilliant at transfering heat, it will probably not be nessecary to disassemble. Most weldings of broken skegs are made without disassembly, even if break is only 1 1/2" inch from gear housing. Perfectly all right. Several outboard repair shops have the equipment, you can ask here for good place near by you. Are you sure the plate wasnt damages during transport and just broke off while you had it.

 

[blklab]

Re: How to Repair Cavitaion Plate

G DANE. thats we were thinking.because we never hit anything while operating the motor. we thought it was strange that it broke without hitting anything.<br /><br />Ed Bures

 

[rdgallo]

Re: How to Repair Cavitaion Plate

You would think you would have damaged the prop or other parts of the lower unit if you caused the cavitation plate to break off. Also, you should see other damage on the plate indicating it impacted something.

 

[blklab]

Re: How to Repair Cavitaion Plate

Ron there is no other damage other than some small scratches on the outer blades where the motor scraped bottom as we beached shored the boat. the Cavitation plate has no scratches or gouges out of it it looks bran spanking new other than the broken piece.

 

[FlyBoyMark]

Re: How to Repair Cavitaion Plate

hmmmm.....wonder if it had one of them thar dolfan fins onit befer <br /><br />Seriously, I've owned a fab shop for twenty years, did marine and aerospace fabricating and welding plus all the junk steel stuff. TIG or MIG weld new piece. Welding over a crack in aluminum will not work, it will crack again. Bevel the "new" scrap piece edge and edge on lower unit at 45 deg. bevel, clean paint off about 1" back from welding area, use 5356 filler ONLY!!! Use vise grips and a small piece of steel to back up new piece while tacking, tack both sides before welding, heat wont affect unit unless plate is broke flush with lower unit leg and you are within a couple of inches of a gasket. When done welding, grind with sanding disk starting at 60 grit lubed with Formax F-26 or candle stick wax if Formax is not available. When shape is aquired, finish grind with 180 grit then acid wash, alodine, green zinc chromate, pick your finish color...

 

[blklab]

Re: How to Repair Cavitaion Plate

FBM WOW

 

[blklab]

Re: How to Repair Cavitaion Plate

FBM WOW THANKS FOR THE INFO.

 

[blklab]

Re: How to Repair Cavitaion Plate

]<br />DOUBLE POST SOORY

 

[RRRKKK]

Re: How to Repair Cavitaion Plate

Iv'e broke several, and had them welded back on with a piece of aluminum. did you have the boat in any place where it could have encountered a sunken limb or stick. Sometimes a stick will lodge between prop and plate and plate breaks, no evidence of hitting anything,

 

[blklab]

Re: How to Repair Cavitaion Plate

Ron we were on a flooded River but never hit any logs or brush. I know it is very possible but we were extremly maybe over cautious. It sounds like welding a piece is our best route unless Johnsons warranties the piece. My father n law talked to the owner of the dealer and he thought maybe they over tightend the directiona l fin on the motor. either way I need to get it fixed due to cosmeticly bothering me,

 

[blklab]

Re: How to Repair Cavitaion Plate

Johnson called the dealer today and they are going to warranty the Lower Unit but Inned to pay for Labore.l $200 which is better than the 800.00 to replace it. thanks to all that replyed.