Yamaha 2B problems

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jav301

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I'm tearing whats left of my hair out over this.

I bought an old Yam 2b a while ago. It ran fine but I was worried that it wasn't circulating enough water. So I took head and leg off to clear the waterways.

Reassembled, all seemed fine., Started easily. But when I went to start it again- no joy. Water is getting into the combustion chamber and wetting the plug so it won't start.

I've changed the gaskets but still water getting in and there's a new symptom. Water is spraying out of the little oil pressure relief channel in the "exhaust plate" (think that's what its called).

Any ideas what can be done?

Thanks
 
jav301 said:
I'm tearing whats left of my hair out over this.

Water is spraying out of the little oil pressure relief channel in the "exhaust plate" (think that's what its called).

Any ideas what can be done?

Thanks
Click to expand...

Are you referring to the exhaust back pressure relief port on the back of the "leg" below the swivel mounting. If so you'd expect to see some water being blown out of there when the engine is running.
I cannot think what else you might mean by "oil pressure relief channel" or what you mean by "exhaust plate"

Perhaps it would help if you were to post links to some exploded diagrams in order to identify the parts you refer to. The parts diagrams on Boats.net are good
 
Did you use a gasket seal with the new gasket? Was there any corrosion? If the wall of the cylinder where it meets the head is at all corroded, then water can get through,
 
Hi,
This is what i think may have happened. Due to insufficient water circulation the cylinder head gasket has gone or warped the head and whilst it wasn't pumping much water it was hardly noticeable. Now you have cleaned the galleries water is flowing to the cylinder head and your seeing water in the cylinder and its causing it to stop. You need to strip it again as you will have water on the crank bearings and these tend to seize quickly. I have had identical problems to this on an identical engine. Sadly i never got it running correctly again
 
These engines are now getting v old, and any corrosion on the thin cylinder wall will compromise it. Try use hylomar or similar with the new gasket - do the head hand tight, allowing the liquid gasket to cure a bit (say a couple of hours), and then fully tighten. That will be your best chance of covering any imperfections around the cylinder. If the head is even slightly warped, or the cylinder wall corroded, it will fail again. But it may just last a while longer.
 
Thanks folks. Sounds like the prognosis is poor. There is significant "erosion" of the metal round the water galleries. I'll try once more with gasket goo.

Vic- the plate I mean is the thick spacer between the leg and the powerhead- gasket either side. There is a small channel to the outside from the void round the "drive shaft".
 
Yep - try once more, and if that doesn't work, either look for a replacement power head on eBay, or sell for spares....
 
VicS said:
Are you referring to the exhaust back pressure relief port on the back of the "leg" below the swivel mounting. If so you'd expect to see some water being blown out of there when the engine is running.
Click to expand...

Apologies for thread hijack, but where else should the water be coming out on a Yam 2B? I have forgotten, don't have (and can't find) a manual, and have become confused about whether I have a cooling problem or not.

I recently restarted mine after a few years not in use (runs fine), and was alarmed that there wasn't water coming out from a hole under the engine as I thought I recalled. I looked for and failed to find such a hole, and concluded I must be remembering water exiting from that location on my previous outboard. I am getting a little water coming out of the location Vic describes (it has a rectangular-ish plastic cover on mine, but just half a dozen small holes in the leg on similar engines), but I convinced myself this must be the main water outlet (having looked at a few videos of 2hp Yams) and that I don't have enough water flowing.

I was thinking the engine would need to be stripped to clear the passageways (and asked about this in a recent thread), but remembered the engine had been professionally serviced not long before it was taken out of commission (due to change in mooring). I seem to vaguely recall I had this service done because I thought there wasn't enough water circulating. I can't recall a problem afterwards, but I now can't remember whether this was because after the service there was an obvious cooling flow coming out somewhere, or just had just assumed the problem was fixed following the service and had never got the engine so hot obvious damage ensued. (It's a bit worrying how I'm struggling to remember any of this, but I have had a lot else on my plate in the intervening years.)
 
LittleSister said:
Apologies for thread hijack, but where else should the water be coming out on a Yam 2B? I have forgotten, don't have (and can't find) a manual, and have become confused about whether I have a cooling problem or not.

I recently restarted mine after a few years not in use (runs fine), and was alarmed that there wasn't water coming out from a hole under the engine as I thought I recalled. I looked for and failed to find such a hole, and concluded I must be remembering water exiting from that location on my previous outboard. I am getting a little water coming out of the location Vic describes (it has a rectangular-ish plastic cover on mine, but just half a dozen small holes in the leg on similar engines), but I convinced myself this must be the main water outlet (having looked at a few videos of 2hp Yams) and that I don't have enough water flowing.

I was thinking the engine would need to be stripped to clear the passageways (and asked about this in a recent thread), but remembered the engine had been professionally serviced not long before it was taken out of commission (due to change in mooring). I seem to vaguely recall I had this service done because I thought there wasn't enough water circulating. I can't recall a problem afterwards, but I now can't remember whether this was because after the service there was an obvious cooling flow coming out somewhere, or just had just assumed the problem was fixed following the service and had never got the engine so hot obvious damage ensued. (It's a bit worrying how I'm struggling to remember any of this, but I have had a lot else on my plate in the intervening years.)
Click to expand...

The bulk of the cooling water exits with the exhaust gases under water.

The 2hp models just have back pressure relief ports on the leg , under a cover, from which some water will be blown

Larger models also have a telltale ( pee hole) under the engine from which there should be a good stream of water if the pump is pumping OK. It is only a telltale though, to show that the pump is Ok. Water from there does not guarantee a flow through the engine itself.

The position of thsee outlets is shown in the owners manual.
 
Thank you, Vic.

I have found a combined Owners Manual on the web for later versions of this motor together with 3,4 and 5hp ones. It does indeed show water coming out where you describe. The 3, 4 and 5hp motors have a different outlet under the motor.

It says "2 [hp] Check for a flow of water with exhaust gas from the hole on exhaust cover'. Interestingly, unlike for the 3, 4 and 5hp, it doesn't say continuous flow. Perhaps I have been expecting more of a flow than I need, though I still suspect mine is on the light side - I get dribbling at tick-over and semi-continuous spitting at speed.
 
LittleSister said:
Thank you, Vic.

I have found a combined Owners Manual on the web for later versions of this motor together with 3,4 and 5hp ones. It does indeed show water coming out where you describe. The 3, 4 and 5hp motors have a different outlet under the motor.

It says "2 [hp] Check for a flow of water with exhaust gas from the hole on exhaust cover'. Interestingly, unlike for the 3, 4 and 5hp, it doesn't say continuous flow. Perhaps I have been expecting more of a flow than I need, though I still suspect mine is on the light side - I get dribbling at tick-over and semi-continuous spitting at speed.
Click to expand...

We have a 2HP Yam. It spits a moderate amount of water at speed. not a lot idling. I have had the head off and cleaned out the water passaged with wire and a hose. Much improved. Used new genuine gaskets. If the impeller is OK, don't worry too much. It's not difficult to strip down, even on a pontoon!
 
That's a great resource, thanks. As for my engine, gasket goo didn't fix the problem so I don't think it is going to run again. I'll be taking it apart to investigate further. If anyone is in desperate need of hard to find spares PM me and I'll see if I have what you want.



LittleSister said:
Stumbled on this American magazine 'PBO' type article on stripping down and rebuilding a 1989 Yamaha 2hp o/b that might be of interest to other owners http://www.sailmagazine.com/boatworks/OutboardRebuildFull.pdf

Curiously, though they replace the knackered impellor, they don't mention cleaning out the water passageways.
Click to expand...
 
Even non runners of this little gem have a remarkable value same model as Mariner and Tohatsu nothing of this weight ( 2 stroke) is allowed for sale in EU any more.
 
parbuckle said:
Even non runners of this little gem have a remarkable value same model as Mariner and Tohatsu nothing of this weight ( 2 stroke) is allowed for sale in EU any more.
Click to expand...
Hi not being pedantic but the Yamaha/ Mariner 2hp are a completely different Yamaha built engine. No parts are transferable with the Mariner /Mercury Tohatsu built 2.2, 2.5, 3.3,and 3.5 hp outboard even though they are very similar.
 
LittleSister said:
Stumbled on this American magazine 'PBO' type article on stripping down and rebuilding a 1989 Yamaha 2hp o/b that might be of interest to other owners http://www.sailmagazine.com/boatworks/OutboardRebuildFull.pdf

Curiously, though they replace the knackered impellor, they don't mention cleaning out the water passageways.
Click to expand...

Thanks for the link. It will be useful once I manage to sort out a leak that I have on the water jacket (to the outside). I haven't used the engine much lately because I tend to prefer rowing or sailing the tender.
 
jav301 said:
That's a great resource, thanks. As for my engine, gasket goo didn't fix the problem so I don't think it is going to run again. I'll be taking it apart to investigate further. If anyone is in desperate need of hard to find spares PM me and I'll see if I have what you want.
Click to expand...

You can always graft an aircooled 4 stroke honda 2.5 hp powerhead on to the leg. Here is one im currently building20150418_092512.jpg
 
steve66 said:
Hi not being pedantic but the Yamaha/ Mariner 2hp are a completely different Yamaha built engine. No parts are transferable with the Mariner /Mercury Tohatsu built 2.2, 2.5, 3.3,and 3.5 hp outboard even though they are very similar.
Click to expand...

I cant deny I am guilty of believing what is often written online about these small outboards being the same but badged engines .
 
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