top of gearbox not flat

[Jerry In Maine]

what can you do if the the top of the lower unit gearbox isn't flat (aside from scrapping the part)?

its not too bad in the region between the front and center screw. looks as though the cooling water flow will not be affected when everything is pulled down tight, but there is a bit of a gap between it and the hard phenolic gasket back toward the exhaust area.

i'd like to mill it down flat - failing that best i can think to do is to add some soft gasket material in the back where the gap is.

[woodbutchergraham]

I would use some wet and dry abrasive on a piece of glass, or a known flat surface and rub the unit flat. Then use a silicone compound to seal the joint up . If the joints not to bad just use silicone, nip the bolts up finger tight so that it leaves a thick joint after 24 hours tighten with a spanner. Works for me but other members may know better!

[Jerry In Maine]

good thinking! i've done that before in other circumstances and can't figure why i didn't think of it this time.

a good way of monitoring progress is to color the surfaceto be lapped with a black marker. The ink will remain in the low spots and will show areas that need work.

thank you for jogging my memory!

[Charles uk]

Before you do anything post a picture of the bend.

[RickUK]

Depends how bad the bend is. DId it occur through rough dismantling?
If there is only a slight curve, which seesm to be the case from your description, the aluminium is quite soft and can usually be rectified by judicious use of a rubber mallet with the part on a flat surface, with slips of wood in the right place to form a bit of a bridge while the the 'blacksmithing' is done.
Probably only a few soft whacks will correct the distortion you mention.
Any kind of a goed fit is really only necessary in the area around the impellor housing.

[Jerry In Maine]

didn't take pics prior to working on this - but the bend was substantial...sort of scary actually. i don't know how it came about. i was reviewing seagull service sheet 9 which mentioned "joint face must be fair and level - check with straight edge". I did and it wasn't.

to fix i coated the surface with dye (so i could monitor progress) and sanded on the belt sander (with a fine grit belt) until i got the section that covers the cooling water plumbing flat. to level the remaining exhaust area i used a metal filled epoxy. this comes in a sort of dough form that you knead to activate. it machines pretty well after curing, takes substantial heat and stands up to fuel. i put a thin layer of this on and sanded until it feathered in.

now its nice and flat and all surfaces mate up nicely.

[Jerry In Maine]

i think another way of getting the surface flat w/o sanding would be to take a bit of sandpaper and just use it to clean the surface. apply a bit of the epoxy dough, then cover it with waxed paper and assemble the parts. the pressure should press the dough to the proper shape and thickness. allow to cure, romove the waxed paper and trim off the excess that squeezed out with a razor knife, then smooth the edges with fine w/d sandpaper.

[Horsley-Anarak]

The couple that I have had that have been bent I straightened by clamping in the vice and using hand pressure.

Take it easy and it should not break.

H-A

[Jerry In Maine]

that "take it easy and it won't break" rule never seems to hold true for me

i'll try that next time. with this one i had almost 1/8" of curve and i thought i'd break it for sure if i tried to bend that out - but maybe not. you guys seem to have good luck straightening them.