Yamaha 5hp 2 stroke

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Laundryman

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I have just bought a used 5hp yamaha 2 stroke which is excellent. Starts first pull, sounds good, pumps water well, amazingly powerful. Puts my 2.7m dinghy on the plane easily. Perhaps I'm looking for faults but im a little concerned about the steam that exits with the cooling water. The water itself, when worked hard is too hot for my hands. I have to admit I took it out for a blast for 30 mins but is the steam normal? If not, how about running it in a strong de scaler in a dustbin. Seller claims that the impeller was reached recently! Advice please. Thanks. Alan
 
Laundryman said:
I have just bought a used 5hp yamaha 2 stroke which is excellent. Starts first pull, sounds good, pumps water well, amazingly powerful. Puts my 2.7m dinghy on the plane easily. Perhaps I'm looking for faults but im a little concerned about the steam that exits with the cooling water. The water itself, when worked hard is too hot for my hands. I have to admit I took it out for a blast for 30 mins but is the steam normal? If not, how about running it in a strong de scaler in a dustbin. Seller claims that the impeller was reached recently! Advice please. Thanks. Alan
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Clearly not cooling properly if you get steam from the tell tale or the exhaust back pressure relief port. Usually telltale streams are no more than luke warm

If you trust what the vendor claims about the pump impeller circulating a suitable descaler might be worth a try. Rydlyme marine descaler or Fernox DS-3 descaler from your plumbers merchant perhaps.

You need to get it running so that you can touch and briefly maintain finger contact on any part of the cylinder block and head with the exception perhaps of the head close to the spark plug (s) and an uncooled exhaust manifold cover if there is one.


Alternatively take it back and ask for your money back.
 
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I have recently bought the same model engine and no, it doesn't make any steam. After a fairly hard 40 mins running yesterday, the cooling water tell tale was barely luke warm. When you say the engine will get your 2.7m dinghy on the plane, with what sort of load is that? Mine will get my Avon Riblite 260 (38kg) on the plane with me, but not with any additional weight. I'm wondering if the dinghy's a bit heavy, the engine's not producing full power, of if I'm just a fat git!
 
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I had one of these excellent engines for about 13 years until early this year. The telltale stream never looked particularly strong but the engine never overheated and I was advised that all was OK. The telltale was never more than warm and I never saw steam in the exhaust output.
The O/b was used to drive a 19Ft daysailer which displaced a little over a ton and I am fat git also so it is unlikely that you are overloading it; however I never drove it hard.
I don't have a technical solution to your problem but I hope this helps setting out what normal running is like.
 
I have a Mariner 5 2-stroke which I presume is much the same engine; as others say the telltale water should only be luke warm.

Could well be salt build up in the waterways, a head off job so a new gasket, otherwise simple.
 
Goldie said:
I have recently bought the same model engine and no, it doesn't make any steam. After a fairly hard 40 mins running yesterday, the cooling water tell tale was barely luke warm. When you say the engine will get your 2.7m dinghy on the plane, with what sort of load is that? Mine will get my Avon Riblite 260 (38kg) on the plane with me, but not with any additional weight. I'm wondering if the dinghy's a bit heavy, the engine's not producing full power, of if I'm just a fat git!
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Hi, I have a Wetline 265 air deck @ approx 30kg and I weigh 40kg. I've only tried it once on Saturday on flat water but was shocked when I clocked 15 knots on my handheld GPS. I would not want to go any faster in my dinghy! Thanks. Alan
 
I have the same engine and although it starts first pull, at present it doesn't push any water through it at all. Does anyone possibly have a manual?
 
Sorry I don't have the manual to hand, but I bought the thing new so presumably have it somewhere, if I find it I'll let you know !

However you and the OP Laundryman really need to get the head off and sort out the salt blockages which I am sure are your problems; quite easy, just 4-5 bolts, if in need of new gaskets try Ron Hale Marine, Portsmouth who do a mail order service - last I heard they were still supplying electric charging coil kits too which may be of interest.
 
problem with old 5hp yam was when gearbox taken off the watertube has a small rubber seal at the top which can be sortof skewed when fitting a new impellor typicaly causes steam when not quite seatedright might not be that but ....
 
fergie,

never had that problem and it's sadly decades now since I bought my Mariner 5 !

Well worth a thought, but I'd bet my left wotsit the snag the people here have is salt build-up in the water galleries...
 
It was quite easy to do by accident . seal is not quite the right description ,its sortof a grommet thing and it gets soft as it gets old, the water tube catches the edgeof the grommet,seal and it crumples restricting/ feeding some water (not enough) to the head and the rest leaks back down the leg
 
Seajet said:
Sorry I don't have the manual to hand, but I bought the thing new so presumably have it somewhere, if I find it I'll let you know !

However you and the OP Laundryman really need to get the head off and sort out the salt blockages which I am sure are your problems; quite easy, just 4-5 bolts, if in need of new gaskets try Ron Hale Marine, Portsmouth who do a mail order service - last I heard they were still supplying electric charging coil kits too which may be of interest.
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Thanks Seajet, great stuff. :)
 
fergie_mac66 said:
It was quite easy to do by accident . seal is not quite the right description ,its sortof a grommet thing and it gets soft as it gets old, the water tube catches the edgeof the grommet,seal and it crumples restricting/ feeding some water (not enough) to the head and the rest leaks back down the leg
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Gosh long shot! Mind I had exactly the same problem a year or so back - rubbed seal with grease and reassembled after half hour and problem solved. Only thing is, my pee-hole flow was sputtering and feeble when it happened and OP seems to report a good flow?
 
James W said:
I have the same engine and although it starts first pull, at present it doesn't push any water through it at all. Does anyone possibly have a manual?
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There is an older Yamaha 5HP version that is air cooled - sure yours isn't that one if there is no water at all? The old 5bs air cooled was an absolute gem of an engine - no impeller, no water ways to block - and not much noisier than the water cooled one.
 
dartmoor said:
There is an older Yamaha 5HP version that is air cooled - sure yours isn't that one if there is no water at all? The old 5bs air cooled was an absolute gem of an engine - no impeller, no water ways to block - and not much noisier than the water cooled one.
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Unfortunately not, it's definitely just a clogged up water cooled! :rolleyes:
 
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