Refit the new seal into the front half using a large socket/drift(writing side to face outward)

drift in the new bearing - it doesnt matter which way round

drift the other new bearing onto the rear of the crank

set up the rear half flat on a workmate/blocks so the crank/rear bearng is vertical and will be assisted by gravity as it is drifted in. dont bash the threaded end of the crank - make up a 2" dia 6" long tube and use that over the crank end

when fully in, replace the rear circlip, new seal(writing side out), castelated spacer, and large circlip

Ensure mating surfaces are free from grit/rust/grease/protrusions/dents etc

use hylomar blue general purpose gasket sealer (the best non-setting)

make a new gasket out of gasket-paper for the cylinder, gearbox in the following way..

cut the paper roughly an inch too big all round

place it over the crankcase-cylinder hole or crankcase gearbox face

make holes to fit over studs/dowels

mark hole centres with a pen on the paper

use 1/4" sockets of about 7mm with bar to punch holes out on bench

tap out the middle and discard

use a light panel pin hammer to tap at 20 degrees into the cavity, thus breaking the paper along the internal edge of the crankcase

tap away the excess from the edge as above

The crankcase halves are just sealed with hylomar- no gasket

make sure you first clear out the drain plug hole

Magneto

make sure you use new/ clean points

feed the HT through the grommet

feed the stop wire through the grommet

replace 3 base plate bolts to marked timing position, or halfway on the slots if you forgot

make sure no wires can get near the flywheel by going under base plate rather than over it

Woodruff key, Flywheel, Nut (no washer) Tighten nut by blocking crank with hammer shaft

You then need to check/adjust the boss is lined up to allow the allen bolts through

Wrong

Correct

The nut can be adjusted so it is tight enough not to fall off, but easy enough to get off in the boat using spanner/hammer if the points need servicing. its best to tighten rather than loosen off, but not too much. torque should be less than 50ft.lbs?

The piston is refitted the right way round, and its ring dowels lined up with the ring-splits. the cylinder bootom is chamfered out to make it easy to slide the cylinder over the rings - provided you squeeze in the ring ends around the piston (making sure all the trime it is astride the dowel) with finger pressure. dont force anything, as it should be easy or there is something wrong! use plenty of oil on the rings.

When the entire piston is in, it should be a sticky but easy sliding fit

The cylinder gasket  is best sealed onto the cylinder, and not the crankcase to give you a good chance of reusing it onboard in case of probs (worth making a spare)

cylinder nuts should not be overtightened, since thay are inaccesible, and soft(there is no compression forcing it up unlike cyl.head bolts)

you will need to tighten the cylinder down gradually a couple of turns for all three nuts at a time, then one flat at a time until all 3 are even. I found a 15mm ring spanner for the rear, and a 12mm open end for the front 2 ideal.

Refitting Gearbox, requires shimming. You need to

replace shims, plate, taper-bearing-race in the crankcase rear

 

place engine front down on workmate/carpet

add gasket you made in place over dowels

line up gearbox outputshaft dog with crank end dog

lower onto dowels

tap home around the gearbox flange

tighten up 2 or 3 bolts

measure the output shaft end play is free running but no end play (<10thou) if not, you can remove gearbox, and add/remove shims behind the race.

finally seal gasket with hylomar and bolt up.

refill with fresh mariised engine oil, hypoy, or any engine oil will do.

replace dipstick

check you have no leaks by leaving it clean overnight, or it will be a lot more difficult to fix on the boat.

Output shaft removal

heres a pic of the output shaft which rusted up in my legacy gearbox

To remove the output shaft, you will have to remove

the rear flange nut and flange itself with the flywheel tool or puller

the gear lever cotter pin which then allows the lever's actautor bearing to swing clear enough of the outputshaft as it comes out

you might also need to remove

the water pump to remove the leyshaft circlip?

the reversing gear which is a push fit into the casting

replacement is reverse (excuse the pun)