Tohatsu 50Hp Project

watersidemat · 06 November 2016, 12:43

Hi all,

So you might have seen a couple of posts about this engine already but I'm just going to put it all in one thread for simplicity sake!
I took this engine out for a spin when i first got it and it wasn't exactly a success!
So its now a bit of a project, made interesting by the fact before starting this my mechanical knowledge basically meant all i knew how to do was add fuel and change a spark plug if i was feeling frisky.

So a bit late but this is the before during and hopefully after, and this thing should...move?

So long story short, I wouldn't use this as a how to but more of a what can you learn from google, you-tube and you lot from Rib.Net! so wish me luck because i have not faith in my ability!

More stuff to follow.

watersidemat · 06 November 2016, 13:51

Righto, first run out (i wont bore you with the video) the engine wouldn't run at full power, it revved quite low and didn't go particularly fast, later, the spark plug in the bottom cylinder blew out at that signaled the end of that run. the plug may have blown before and may be the cause of the lack of power. When trying to cavitate the engine in turns the engine would rev up high as expected but would drop off and lose power as the water settled around the prop.

So when the cover came off the engine was very dirty and caked in gunk and grease. I uses some hyper clean degreaser on it and pressure washed the whole thing. alot of the paint came off but at least now its clean.

Work done so far:
Cylinder head sent off to be re threaded
Engine block cleaned and painted
New bolts and gaskets for Cylinder head
Piston heads cleaned
Recoil assembly removed and painted
Flywheel cleaned and sprayed with corrosion inhibitor.
fuel filter replaced
New anode inside the cylinder head under the thermostat, (there wasn't one before)
air silencer cleaned, it sucked in some gunk from the engine
re connected up some unconnected linkages!
new odds and sods ordered, blots and screws mostly.

Still waiting on the Cylinder head bolts then it can be put together.

Jobs on going or next:
Finish painting the engine
fit cylinder head
clean the carbs
get it running!
hopefully not change the coils!

so that should keep me busy for the next few weeks.

Attached pictures of some 'before'

watersidemat · 06 November 2016, 13:53

Some During/After photo's

watersidemat · 06 November 2016, 13:56

Couldn't fit more than five images, the engine leg being painted, so far just got some red oxide primer to give it some body, the paint on it before all flaked off under pressure washer so its been sanded down, wet and dry and now painted, have some black spray paint to get on it next.

Roflhat · 08 November 2016, 13:58

I would definitely check whether you've got spark going to all cylinders, probably worth replacing the plugs anyway. Tohatsu coils are expensive, you can use lots of various other coils instead.

Also clean the carbs, 9 times out of 10 when an engine isn't working properly its fuel related

watersidemat · 08 November 2016, 15:35

New plugs are ready to go, the other set when I took it out first were 1 the wrong plugs and 2 rusted

I have a can of corn clean, when the engines running I'll spray that into them see if that does it, I have some redex stuff for the fuel tank and out in a new filter, hope that will do, don't want to dismantle the carbs

beerbelly · 08 November 2016, 17:56

when you primed the leg did you etch prime any bare alloy. alloy must be etch primed before priming as adhesion will be seriously affected if not. same with painting plastic parts they must be given a light coat of adhesion promotor prior to priming. just trying to help

69cmw · 08 November 2016, 18:34

Quote:

Originally Posted by beerbelly

when you primed the leg did you etch prime any bare alloy. alloy must be etch primed before priming as adhesion will be seriously affected if not. same with painting plastic parts they must be given a light coat of adhesion promotor prior to priming. just trying to help

Worth listening to as beerbelly is a spray painter to trade [emoji106]

watersidemat · 08 November 2016, 20:48

Quote:

Originally Posted by beerbelly

when you primed the leg did you etch prime any bare alloy. alloy must be etch primed before priming as adhesion will be seriously affected if not. same with painting plastic parts they must be given a light coat of adhesion promotor prior to priming. just trying to help

Didn't take it right back to bare alloy, there was some blue left on the leg, theres some bare patches but just small patches of that.
its been wet and dry sanded then cleaned and sprayed with TK Colourspray Anti Rust Engine Spray Paint - Grey - TK Colourspray - Discount Marine Chandlery and Sailing Equipment. Bargain Boat Spares and Clothing then red oxide over that.
the only plastic bit is the apron (missing from the leg in the photo) and thats been sprayed with TK Colour spray. I'll find out if it holds on its next run.

watersidemat · 29 November 2016, 19:24

So small update, cylinder head is back on and new ignition coils and boots fitted.
carbs are off for cleaning and leg is painted and gearbox oils changed.
prop fitted and its slowly coming together.

next job in the next few weeks is to fit the cabs back on, install an external fuel filter and put in a new tank. pressure test the new head and then hopefully it will start!

spartacus · 29 November 2016, 21:41

Good job.

9D280 · 30 November 2016, 00:15

Stop it.......

you're putting me in the mood to rebuild something else!

Joking aside, I had mine apart to the point of re-boring the cyls & going up a piston size. At least when you rebuild you know when you are out there that the engine has been built properly, and any dodgy history has been removed.

Roflhat · 30 November 2016, 22:04

Nice one, if you get the chance it's worth getting the crankshaft welded, it stops the journals rotating which can happen when loading and unloading the engine, for example running in surf or waves. Also means you can cut the rev limiter, all the other components can take the extra rpm
I would also check your engine mounts, tohatsu ones aren't much good. Better to replace with poly mounts or solid. Most of the mods done for zapcat racing are longetivity/reliability related as opposed to performances

watersidemat · 02 December 2016, 14:36

well i got it running, though it's not quite right.

first issue is some water bubbles out from the top of the cylinder head, i'm worried it's also leaking the cooling water into the cylinders! i think there were water droplets on the spark plug threads when i took them out to clean the oil off them.

tried to adjust the carburetor fuel screws but thats didn't seem to do much at all so need to investigate that further.

might be a case of taking the head back off and putting some liquid gasket sealant on the gaskets and try again. need to get a compression tester and check that too then play with the carbs again.

watersidemat · 02 December 2016, 16:33

The water leak is coming out from this corner of the head by the closest thermostat screw. Any ideas?

spartacus · 02 December 2016, 16:53

It shouldn't need liquid sealant. Was the head spotless (remove all the old gasket with a Stanley blade). Any corrosion on the water channels or the mating surface of the cylinder head and engine block? Could take the head off and get it lightly skimmed.

Regards running, I had a similar problem with my Tohatsu M60. Stripped the carbs numerous times and adjusted the fuel screws (from memory 1½ turns out from lightly seated). Ended up putting to the engineers at Mackay Marine in Aberdeen who basically released the throttle and carb opening mechanism and started from scratch to ensure everything was in sync. Runs like a Tag Heuer watch now.

watersidemat · 02 December 2016, 17:04

https://www.youtube.com/watch?v=y3vhl4uBrVM

watersidemat · 02 December 2016, 17:14

i'd like to avoid getting it skimmed if possible, will have to take the head off and try cleaning it up again and put it back on, i won't have to replace the bolts again will I? they are all brand new!

jeffstevens763@g · 02 December 2016, 17:58

Correct torque on bolts, tightened in correct sequence, head checked for warp, clean head & block no cracks pits etc, new gasket could be a dud about all I can throw in don't know about bolts are they a one hit dealer should know.
Did you run till warm let cool then re torque head bolts
Cheers

spartacus · 02 December 2016, 22:04

I'm sure the bolts are stretch bolts, but bollo**s to replacing them. The gasket is damned expensive too. Looks like you need to take the cylinder head off, its leaking, so you've no choice. Run a metal ruler over the mating surfaces to look for a true edge. The temptation is to tighten the gasket further, but that's short-lived. Because it's already compressed, you can only tighten a little further, but definitely look at the head being lightly skimmed.