Yamaha water stream...does this look OK?

Iain C

Iain C

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Right, down to the boat next weekend and I will be trying out the combination of my new (to me) Avon Rover R2.80 and the Yamaha 5C longshaft 2 stroke. Yes, I know a short shaft is better, the engine has come off my day sailer project and I hope to put it to good use in the meantime!

However, compared to the exhaust stream on my little Suzuki DF2.5 (let's call that one the "8 pints of Stella and would you believe it the toilet on the coach was out of order the whole way home" effect), the Yamaha is a bit lacking (let's call that one the "I know we have 3 back to back races in the 49er today and I've just been 20 minutes ago but it's windy and getting a trapeze harness off is gonna be a nightmare" effect). I've checked the impeller and all the vanes are there (granted a few were the wrong way round but this is now fixed)...does the panel think this looks normal for a 5 HP 2 stroke?


Thanks
 
I'd have expected a more constant stream; it does look like a fair bit of water going through though.

Put your hand in the flow, that's your temperature guage; it should only get to luke warm, any hotter and there's a problem, very likely a build up of salt in the waterways.

I have a 4 hp Yamaha and 5hp Mariner, both 2-strokes.
 
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Iain C said:
Right, down to the boat next weekend and I will be trying out the combination of my new (to me) Avon Rover R2.80 and the Yamaha 5C longshaft 2 stroke. Yes, I know a short shaft is better, the engine has come off my day sailer project and I hope to put it to good use in the meantime!

However, compared to the exhaust stream on my little Suzuki DF2.5 (let's call that one the "8 pints of Stella and would you believe it the toilet on the coach was out of order the whole way home" effect), the Yamaha is a bit lacking (let's call that one the "I know we have 3 back to back races in the 49er today and I've just been 20 minutes ago but it's windy and getting a trapeze harness off is gonna be a nightmare" effect). I've checked the impeller and all the vanes are there (granted a few were the wrong way round but this is now fixed)...does the panel think this looks normal for a 5 HP 2 stroke?



Thanks
Click to expand...

Looks OK at tick over hopefully a stronger stream when running. Does not look like its in deep enough water for a proper test anyway. Looks like you are trying to do it in a bucket!

Stupid putting an old semi-knackered impeller back in. While its it bits put a new one in!


Check the tempearture of the power head when running. You should be able to touch and maintain brief contact with almost any part . If you cannot then its overheating.

Pee stream is unlikely to get hot except in extreme cases as its just a telltale to show that the pump is pumping and the water probably has not circulated through much of the engine
 
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Iain C said:
Right, down to the boat next weekend and I will be trying out the combination of my new (to me) Avon Rover R2.80 and the Yamaha 5C longshaft 2 stroke. Yes, I know a short shaft is better, the engine has come off my day sailer project and I hope to put it to good use in the meantime!

However, compared to the exhaust stream on my little Suzuki DF2.5 (let's call that one the "8 pints of Stella and would you believe it the toilet on the coach was out of order the whole way home" effect), the Yamaha is a bit lacking (let's call that one the "I know we have 3 back to back races in the 49er today and I've just been 20 minutes ago but it's windy and getting a trapeze harness off is gonna be a nightmare" effect). I've checked the impeller and all the vanes are there (granted a few were the wrong way round but this is now fixed)...does the panel think this looks normal for a 5 HP 2 stroke?


Thanks
Click to expand...

Difficult to tell from a video. Does the water feel tepid, warm or hot? If tepid, after a decent time running, then I'd say you are ok there. If it gets hot, then it may be some corrosion/salt build up in the passages.
 
To answer a few points...

I agree, I might as well put a new impeller in, and I will order one. TBH I was half hoping to find mine in bits by way of an explanation but it seems OK, flexible and not cracked.

It doesn't seem to get warm at all, that said it is a noisy old thing and I don't want to sit there with it running full chat in a bucket in my garden for ages (actually the old water tank out of my Sabre before I replaced it with a flexi tank) as it's a little antisocial. However I will give it a good ragging in a non-critical situation on the water and see what happens. The flow does improve a little with revs, but not massively.

The previous owner (of these parts) used it primarily in fresh water and it's generally in very good condition (the leg is much better than my 6 year old DF2.5). However are there any tricks for clearing out the water passages just in case?

I have managed to retro fit a killcord into one of the blanked off slots...was a bloody nightmare (carb off to make room) but it all went back together, tests fine, and I will be much happier using it in an inflatable at speed, so quite chuffed with that!
 
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If the water keeps flowing and doesn't get hot - then take, heart - good sign. Remember that tell tale is just that - so flow could be poor just from tell tale, not the engine itself. So best steps are to poke something up the tell tale to check its clear. You can use something like "salt away" if you want to try that. But basically, it water flows, and its tepid/cool, then I would say you are ok.
 
I run mine in an old watertank.

I run as long as is necessary. With the exhaust outlet properly submerged its not as noisy as the lawn mower esp with the cover on


DSCF0413.jpg


I tried a wheelie bin but discovered a snag if SWMBO happened to be gardening

DSCF0419.jpg
 
Iain C said:
I've checked the impeller and all the vanes are there (granted a few were the wrong way round but this is now fixed)...does the panel think this looks normal for a 5 HP 2 stroke?
Click to expand...

I had exactly the same problem on a 2-stroke Yamaha 2001 8hp. Like you I checked the impeller; that was not the problem, but I replaced it anyway. Water flow still exactly as in your picture.

Next I ran engine in a bin in the garden for about 1/2 hr to desalt it a bit. Powerhead never became overly hot to the touch, but pee-hole flow never improved.

So I disconnected the base of the engine from its upper section -- it's only about 6 bolts and a bit of fiddling -- in order to take a look at the channels leading up to the pee-hole. They were clogged with sand, which I cleaned with a MK1 BBQ stick! From what I could see the salting up in the cooling channels was minimal.

Reassembled the engine, started it and the pee-hole flow trebled -- from c. 200ml per min to c. 600ml per min IIRC. Engine worked fine ever since.

One caveat; this job is not difficult ...BUT, be careful if rusty/seized bolts are a problem. A couple of snapped bolts will quickly change a 1hr job into a 5hr one! FWIW, having seen inside I'd be happy to run an engine in the condition you describe on the basis that the limited water from pee-hole never gets too hot, the power-head remains easily touchable and their is no sign of paint scorching on it.
 
Another vote for some crud stuck somewhere. My Mercury 5hp was doing the same thing at the start of this season after being laid up for a few years. No visible signs of muck in the pipes but the pee-hole flow was quite intermittent. Turns out something was getting stuck over the inside of the pee-hole tube as water flow dried up more the harder it was pumped. Rooting around with a paperclip sorted it out - I wonder if it might have been a flake of paint or similar.
 
Hmmm...as Jimmy Tarbuck would say "a slight difference of opinion here". I think I will do what Dom suggests and drop the leg off and have a poke around. If I can't find anything or improve it, then that's it, however it is bugging me a bit. The video makes the stream look better than it is. I'd expect a solid, unbroken stream, this is more a case of "pellets" of water if that makes sense!
 
That water stream is the tell tale.

The main cooling water exits below water level.

Sometimes a fine wire or stiff bit of thick nylon fishing line inserted (even when running) into that tube tends to dislodge some tiny grit/grain of sand etc.

Try it before going on to more expensive cures/solutions.



PS this issue and solution happens on the larger outboards that I have as well.








An older thread on the 2.5

http://www.ybw.com/forums/archive/index.php/t-314023.html
 
When we first got our Tohatsu 3.5 the tell tale just dripped. Engine never overheated, replaced impeller and tell tale still the same. Took head off and if I recall correctly there was no serious salting, a piece of wire up the tell tale would probably have sorted the problem. To be honest with the amount of water coming out of the O.P's at tick over and no overheating I would not have investigated.
 
I just tested my Yam 9.9. It took 28 seconds for a litre to come out of the pee hole at tickover - which appears to be massively more than yours. It's squirting into the sea like a 5 year old boy, not dribbling like an 80 year old grandad.

Tickover...

L4F1H0F.jpg
 
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Iain C said:
The video makes the stream look better than it is. I'd expect a solid, unbroken stream, this is more a case of "pellets" of water if that makes sense!
Click to expand...

I think it's a bit of a design fault as the cooling water travels along a fairly wide horizontal section before reaching the small pee-hole. So like a river estuary the slow moving water deposits sand particles on the bottom, which in turn binds with mud or salt to eventually constrict the flow. Seems like we're not alone:

http://www.thehulltruth.com/boating-forum/464772-8hp-yamaha-not-pissing-even-new-impeller.html#b
http://svrainshadow.com/?p=447

Incidentally, I tried blasting the gunk out by attaching a bicycle pump with a football nozzle to the pee-hole, but it didn't work.
 
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The Evinrude 4 hp just leaves a trail of water vapour behind it. So, is that better then a strong pee stream or a spurting one, or is it worse?
 
Well, I split the engine from the leg, and from what I can see the engine hs never seen salt water. Everything came apart very easily and it was incredibly clean in the water galleries...shiny ally...I will feel very guilty when I run it in the salty stuff at the weekend!

I ran it for about 5-10 minutes, on tickover and half throttle. The water was warm but never hot, so I think I'm starting to lean towards the "nothing wrong with it" camp. If it survives a good thrashing at the weekend without getting too warm, it's fine.

I'm impressed with the engine...not used it on a boat yet but it seems very well designed and nice and simple. Thanks again for the input all!
 
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