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Old 14 October 2019, 17:03   #1
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Country: UK - Scotland
Town: Inverness
Make: Avon
Length: 4m +
Engine: Yamaha 40hp
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propellor bolt torque for yam 40hp ?

I've spent quite a bit of time searching here and online but can't find an actual nm or lb/ft answer.
I have a 90s Yamaha 40hp engine, obviously 2 stroke. I have fitted a new propeller and have no idea how tight the bolt should be...
Someone else took the bolt off so I don't even have a rough idea, anybody able to advice me on this, thankyou!!!
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Old 14 October 2019, 18:51   #2
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Country: UK - England
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Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Yamaha 15Hp 2-stroke
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Is there a manual here for your model? If not have a look through other 40hp models to get an idea of torque.

https://yamahaoutboards.com/en-us/ho...owners-manuals
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Old 14 October 2019, 23:45   #3
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Country: Australia
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I've never tightened any prop overly hard, simply tighten gently then use a new stainless split pin. Like trailer wheel bearings, don't over tighten them.
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Old 15 October 2019, 04:09   #4
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For the smaller outboards I've dealt with I generally agree jon. I carry a ring spanner about 8" long for prop change and firm hand tight with that has been the correct torque for the 20hp and below motors I've run recently.

I do have some figures in the file as ball park examples but would still prefer the OP starts off knowing the correct figure for his exact model.

2003 Yamaha 15hp - 12.5Nm and tighten further as required to align split pin hole.

2008 Yamaha 40hp - 40Nm and tighten further as required to align split pin hole.

2010 Mercury 40hp - 75Nm (lock washer not split pin).
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Old 15 October 2019, 05:23   #5
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Country: UK - England
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i tighten mine in line with the split pin hole which is usually just nipped up
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Old 15 October 2019, 16:48   #6
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I tighten till the nut contacts then turn far enough to insert the split pin not particularly tight at all, no real need when the splines are doing the work
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Old 17 October 2019, 17:40   #7
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Thankyou all. I may have tightened it to much however due to the refurb I haven't ran it since fitting.
Will undo and follow advice as soon as I can, Great to be part of an old school forum tht hasn't been eaten up by facebook era
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Old 17 October 2019, 20:49   #8
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Quote:
Originally Posted by nousername View Post
Thankyou all. I may have tightened it to much however due to the refurb I haven't ran it since fitting.
Will undo and follow advice as soon as I can, Great to be part of an old school forum tht hasn't been eaten up by facebook era

I've owned boats with outboards for over 40years and only ever lightly tightened them. My current engine Yam f70 which I've clocked 800hrs on in the last two years doesn't even have a locking split pin, neither did the Suzuki 90 before it. The standard nut was replaced on both engines with a prop lock fixing which stops people steeling your propeller.

Has anyone ever had a prop fall off, ive never heard of it over here where every man and his dog owns a boat.
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Old 18 October 2019, 04:00   #9
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New suzuki 140 prop nut was hand tight with split pin in place. Thought strange at the time, but have seen various thoughts on this subject.

I came to the conclusion the thrust when in forward pushed the horizontal movement in the prop hard up against the spline. The opposite in reverse.

So when engaging reverse the prop could move back against the locking nut, if taking up any slack....ie. then causing a knocking noise, then when putting her into forward, same would happen.

So I guess it makes sense to tighten enough to stop any movement horizontally along the spline, stopping the knocking noise, as agreed with beamishken, the spline is taking all the rotational stresses.
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