Yamaha 2 hp outboard impeller

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sailor211

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I have a Yamaha 2 hp outboard 2B 6A1, I think from the mid 1980’s.

This has suddenly started overheating and I suspect either a failed impeller or crud in the impeller. I wanted to get at the impeller housing to investigate so have tried to get off the lower gear housing that has the water pump housing on the top, this has parted and I can see the bit I need to get to. However the drive shaft is stopping the bits it coming apart. I was expecting the shaft to have splines and drop out . This is not the case!

How do I get the thing apart to access the pump impeller

Do I have to:-

1:- Drain the gear box and get the pinion off?
2:- Detach motor from the top end, looks like 6 bolts?

Do something else? is there a better way?

Anyone have a service manual with instructions?
 
sailor211 said:
I have a Yamaha 2 hp outboard 2B 6A1, I think from the mid 1980’s.

. I was expecting the shaft to have splines and drop out . This is not the case!

How do I get the thing apart to access the pump impeller

Do I have to:-

1:- Drain the gear box and get the pinion off?
2:- Detach motor from the top end, looks like 6 bolts?

Do something else? is there a better way?

Anyone have a service manual with instructions?
Click to expand...

The vertical drive shaft should pull out of engagement with the crankshaft. I'm not sure if it splined or just a square but it is probably rusted in esp if the pump has not been regularly serviced and the joint greased before reassembly.

As Awol says there is circlip on the bottom end however I am not at all sure that getting into the gear box and removing that will solve the problem unless the bolts holding the pump housing are accessible as the impeller being pinned to the shaft will prevent its withdrawal.

Ultimately the shaft will have to be pulled from the crankshaft I am fairly sure.
 
VicS said:
The vertical drive shaft should pull out of engagement with the crankshaft. I'm not sure if it splined or just a square but it is probably rusted in esp if the pump has not been regularly serviced and the joint greased before reassembly.

As Awol says there is circlip on the bottom end however I am not at all sure that getting into the gear box and removing that will solve the problem unless the bolts holding the pump housing are accessible as the impeller being pinned to the shaft will prevent its withdrawal.

Ultimately the shaft will have to be pulled from the crankshaft I am fairly sure.
Click to expand...

Yes it looks as if i need to pull the shaft out possible i will have to look at the top end.

Never simple !

You are right it is a mid 1980's engine bought secondhand and after more than 12 years of ownership i am servicing it! but i do not like to play with things that are working
 
sailor211 said:
Yes it looks as if i need to pull the shaft out possible i will have to look at the top end.

Never simple !

You are right it is a mid 1980's engine bought secondhand and after more than 12 years of ownership i am servicing it! but i do not like to play with things that are working
Click to expand...

Not fixing things that are not broken may be a good policy but the downside with small outboards is that they are then very difficult to dismantle.
Routine replacement of a pump impeller is well worth while , just as it is with an inboard engine. and has the added advantage that the bolts and other bits and pieces can be greased on reassembly making the job easier next time.

If the shaft is rusted into the crankshaft you'll not get the powerhead off any easier.
 
sailor211 said:
Thanks that looks the same. Pictures do help

It appears i need to to both.
Click to expand...

We have one of these engines. Our overheating exploits were caused by a build up of salt / calcareous deposits in the engine head. Eventually sorted by taking off the head and cleaning out all the offending waterways with a screwdriver and piece of stiff wire. Several goes and intermediate flushes later it was fine.
I ended up buying a few new gaskets mind you as the exhaust labyrinth at the base of the motor block needed the same clean out!!
You can get good service from Caley Marina workshop / chandlery in Inverness. They were both knowledgeable and friendly re these small Yams, and happy to post stuff off.

The problem is compounded as the hotter the get - the more deposits come out of solution and clog things even more.

Graeme
 
Can confirm that the drive shaft has a square connection and is very likely to be rusted so likely to need some force to separate. The circlip under the pinion will have to be removed to access the impeller. You will almost certainly have to replace the housing as well (used to be available as a kit together with impeller). As pagoda says the waterways in the head will probably need scraping out. (Shortly after doing all the work, mine 'disappeared' from the dingy one dark night in Chi Hbr :( )
 
sailor211 said:
Thanks all , it will take a little longer than I hoped but now I know what I am doing !
Mike
Click to expand...

Have just done this on mine and can say take the power head off as well as drain the gear box and remove the prop shaft and gears. Then remove the circlip at the bottom of the shaft and the three screws binding the lower assembly to the upper part of the shaft tube. Finally insert an appropriate size socket into the shaft tube housing to sit on top of the square inner shaft. A few gentle taps should have the lower assembly sliding away from the upper shaft assembly and reveal the impeller.

Reassembly is pretty straight forward but put some thought into the direction of turn for the impeller. The fins should trail the direction of rotation.

Sing out if you have more questions as it's all pretty fresh in my mind.

Cheers PT.
 
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