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Old 25 August 2009, 15:44   #1
Country: UK - England
Town: Essex
Make: Walker Bay Genesis
Length: 3m +
Engine: 15HP Mariner 2s
Join Date: Jun 2009
Posts: 10
Lifespan of Yamaha 4 stroke 4hp Outboard


I have been offered a 4hp Yamaha 4 stroke 2005 outboard for 350.

The engine has been well cared for and serciced, but has done 130 hours....

What amount of hours could I realistically expect before starting to get problems....


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Old 25 August 2009, 17:25   #2
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Country: UK - England
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Engine: Tohatsu 9.8
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Engine life

If the engine has been looked after with regular oil changes/lubrication etc it should last thousands of hours before anything starts to wear, or it begins to burn oil.
I've got a Honda 100cc motorbike with a single cylinder 4 stroke engine, it was my first vehicle in 1979 and has done over 70,000 miles. It's been thrashed, crashed, immersed in water (stolen and recovered after being hammered round a field until it ran out of fuel and then dumped in a river) ridden flat out for hours (9-10,000rpm) and serviced from time to time.
The engine has never needed anything, the head has never been off and it has never been apart. I restored the bike some years ago but left the engine as it was, just painted the fins/crankcase to make it look better. It still performs well, top speed 60mph at 10,000rpm.

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Old 25 August 2009, 18:12   #3
Country: USA
Town: Seattle
Boat name: Water Dog
Make: Polaris
Length: 4m +
Engine: Yamaha 60hp
Join Date: Apr 2007
Posts: 1,152
Even well cared for outboards start to get tired. with poor care around 400 hours. with excellent care probably 2x that (800 hours). Most outboards are not going to be performing optimally at 1000 hours.

In your case I could guess its ~20% through of its useful life. Probably got more than 80% left but I wouldn't count on the previous owner for that.
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Old 26 August 2009, 06:42   #4
Country: UK - England
Town: worcester
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800 hours does not seem long for a well looked after engine, it's just over three months continued use. Think engine hours are a poor way of judging the condition of the engine. Lots of shorts trips and high speeds will cause more damage as the oil is cold. Most sailing schools change the outboards on their rescue boats are three or four years and they have had a lot of use and no where near redundant and still have plenty of life left in them. Working overseas we have noticed that four strokes are harder to service and are very sensitive to inaccurate tuning. I believe Honda are now offering a six year warranty on their engines which is a measure of current reliability.
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Old 26 August 2009, 10:02   #5
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 378
Its certainly difficult to relate the condition of an outboard motor to engine hours. I reckon corrosion is always going to beat "wear" in determining the length of a motors life unless it is run all day every day in an commercial environment clocking up 1000s of hours.

Considering an average car engine still has loads of life in it yet with 100000 miles on the clock and guessing at an average speed of around 30mph this equates to 3300 odd hours.

Obviously car engines run in a much friendlier environment but they also regularly cover 20000 miles without an oil change. Assuming 30mph average again this is 660 hours between services. A 4 stroke outboard being serviced once a year and used for leisure purposes will probably have its oil changed around 20 times by the time it reaches 600+ hours. (I think most leisure users only manage around 30 hours a season)

I'd prefer an 2 year old motor with 1000 hours than a 10 year old one with 500.

Back to the origional question I reckon most of the small self drive hire boats around here (typicall 4-6 HP Yams) will clock well over 130 hours a month if not double in some cases and these seem to last around years before they are replaced...
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