Yamaha 2B Outboard

[VicS]

Thank you for info. Outboard serial number is 6A1 050363 but don’t how that ties down the year of manufacture.

Sorry for delayed reply. Been away since last Wednesday

I think that makes it a 1982 model but there should be a date letter on the ID plate.

If in fact 1982 I don't know where one would find a Yamaha parts list except for a Mariner which in those days were rebadged Yamahas

https://www.marineengine.com/parts/mariner-outboard-parts/2b/6a1000101-and-up-m/gearhousing-assembly may be relevant

but if no water is pumped when the lower unit is tested in a bucket with an electric drill ( assuming the pump is adequately submerged ) I'd check the pump impeller and its drive pin , #24, in the above diagram.

 

[SteveIOW]

Thank you for all your advice. Am just about to reassemble pump and outboard with all new service parts but have yet one more query before I do so: The photos show the top half of the pump housing. You will see there are three small round holes at the inside edge of the flat surface which go right though the casting. Is this correct? One seems to have the remains of a tiny grommet in it. What is their purpose? I want the water to go up the pipe to the power head not leak away elsewhere. Sorry to keep this saga going.

 

[alahol2]

I think the thin stainless 'gasket' (part number 15 above) that sits between the two halves of the pump blocks those holes. So they don't really serve any purpose nor would they be detrimental.

 

[SteveIOW]

Outboard now all back together with all new pump components, seals, gaskets, lubricants… Ran engine in deep bucket of water (started first pull) but even allowing it to run for some time at quite high revs there was not even a dribble of water coming out of the tell tale hole in the leg. Very frustrating!
Does this DEFINITELY prove that cooling water is not being pumped up to the power head? Could not all of the cooling water be coming out with the underwater exhaust?
The holes in leg are not blocked.

 

[alahol2]

There's a good possibility that the waterways in the head are blocked. You will need to remove the upper part of the leg from the head and have a poke/scrape about..

Just noticed you said earlier that you've already done that... At which point I'm out of suggestions.

 

[SteveIOW]

Probably a silly question at this stage but am I right in thinking Yamaha 2B DOESN’T have a thermostat?

 

[SteveIOW]

SUCCESS!!
Removed leg again and proved pump working ok with electric drill turning the drive shaft.
Removed cylinder head and interface plates aground crankshaft again. No obvious blockage until I tracked the route the water actually takes. The water enters the jacket around the cylinder though a nice large slot at the bottom and leaves at the top. It then travels across and down via a “pipe” within the casting. There is a 90 degree bend in this “pipe” which was blocked solid but not visible. White vinegar and boiling water plus lots of probing with stiff bent rods eventually got it it clear. All now reassembled and run in deep bucket of water. Good flow of water coming out of tell tales in outboard leg.
Got there at last. Hope this may help others who experience low/nil cooling water flow with these great little lightweight 2 strokes.
Thanks to those members who have posted help.

 

[VicS]

Thanks for the feed back

.

 

[Mark-1]

SUCCESS!!
Removed leg again and proved pump working ok with electric drill turning the drive shaft.
Removed cylinder head and interface plates aground crankshaft again. No obvious blockage until I tracked the route the water actually takes. The water enters the jacket around the cylinder though a nice large slot at the bottom and leaves at the top. It then travels across and down via a “pipe” within the casting. There is a 90 degree bend in this “pipe” which was blocked solid but not visible. White vinegar and boiling water plus lots of probing with stiff bent rods eventually got it it clear. All now reassembled and run in deep bucket of water. Good flow of water coming out of tell tales in outboard leg.
Got there at last. Hope this may help others who experience low/nil cooling water flow with these great little lightweight 2 strokes.
Thanks to those members who have posted help.

Thanks for sharing. Google loves YBW so I'm pretty sure your posts will help someone struggling in future.

 

[deeky]

google does seem to like this forum, its the future, im struggling, and this helped