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Broken cavitation plate question Honda BF 135

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fiddlebick

New member
Hit a log and broke not only the cav plate, but the trim tab snapped too. I'm having trouble finding anyone that can both repair/weld the plate and also have the capability to machine the recess for the trim tab to mount. ...soo thinking about buying a new lower unit case (only) and swapping the gears, with the help of a capable friend. I'm an industrial mechanic by trade, but know nothing about rebuilding a lower unit. I do however firmly believe that I can do the work if I have access to the correct information. Does anyone know where I can access a shop manual or the info therein for setting the gears on these motors?
 
I wouldn't trust anything other than the official shop manual to get the selective shims installed properly setting up the gearcase. Costs more but does so much more for you.

The following link takes you (I hope) to the page where you need to scroll down and find the appropriate SI for your outboard.

https://publications.powerequipment.honda.com/marine

Good luck.
 
Machine the recess for the trim tab ----BEFORE ----The welding.------Just had welding like that done on an Evinrude V-6 gearcase.------Go fast " lightning " gearcase.-----No way would I buy a new one of those.----Cost me $100 for the welding.-----Thinking of having it powder coated.
 
Not following. The welding process is going to partially fill that recess (it sounds like). That excess weld will need to removed and smoothed, which sounds like Dremel work if I were doing it - AFTER the welding. Or maybe I'm missing something?
 
Pardon me for asking such a dumb question. I thought maybe an expert like you might be willing to share some of his vast experience....
 
fiddlebick said:
Hit a log and broke not only the cav plate, but the trim tab snapped too. I'm having trouble finding anyone that can both repair/weld the plate and also have the capability to machine the recess for the trim tab to mount. ...soo thinking about buying a new lower unit case (only) and swapping the gears, with the help of a capable friend. I'm an industrial mechanic by trade, but know nothing about rebuilding a lower unit. I do however firmly believe that I can do the work if I have access to the correct information. Does anyone know where I can access a shop manual or the info therein for setting the gears on these motors?
Click to expand...

The problem with doing this yourself is the cost of the necessary tools to calculate shims.Not an easy task if you haven't done it before. We get them welded all the time, it would b more cost effective to weld been if you have to freight it to a competent welder
 
???----It is much easier to put a piece 1/4 or 5/16" aluminum plate onto a milling machine to do the recess for the trim tab BEFORE the main welding.-----90% of the work done and 10% finishing after the welding.-----Note ----I was doing some aluminum TIG welding over 40 years ago at a training center.----Instructor came by and said ----" Looks like you have done this before too "
 
OK, so now I have a piece of alum. plate with a great looking relief cut into it that fits the trim fin perfectly. Now what? Mill an area the size of that plate from the lower unit and weld that in as part of the repair?
 
Thanks for all the good info. The gear case alone new is around 750 bucks. A shop manual is 125. I like the idea of shipping it off to a professionial outboard repairman. The local welding shop balked when I told them the tab recess would have to be machined to fit.
 
How handy are you? Do you have a Dremel tool and a little patience to do some alum. carving? It wouldn't have to be perfect to work just fine.

Still think the used idea is viable as well. Having a decent shop replace that case isn't going to be cheap! So 750 + labor!
 
OF COURSE THE BIG UNKNOWN IS THAT HAVING HIT SOMETHING THAT HARD WITH THE LOWER UNIT, ARE ANY OF THE GEARS Damaged. (sorry for the caps)
 
Prop shaft would be my main concern, and that's pretty easily checked for run out. Could involve something as simple as holding a screw driver near the end of the shaft while somebody turns the shaft. You're mechanic buddy can handle that check easily.

Anything is possible on the gears, and the shift mechanism, but if it seems to be working OK, I'd run with it. Keep the offshore trips to a minimum until you get a couple of hours on it. If it's going to screw up, it should do it right away in my experience.
 
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