170 conversion long to standard shaft

Having problems with a Seagull? - ask an expert here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

Post Reply
andrew
Site Admin
Posts: 116
Joined: Wed May 24, 2017 5:37 pm
Location: ..

170 conversion long to standard shaft

Post by andrew »

Hoping to convert a 170 from long shaft to standard on a budget (if possible) and need a bit of help please.

There are 6 parts I can see that need shortening:
1 exhaust tube assembly
2 Silencer tube
3 water delivery pipe
4 gear selector rod
5 drive shaft
6 drive shaft casing

First 3 I think I can cut to length, absent objections otherwise.

Gear selector rod I can cut but would have to rethread that and the yoke to metric/imperial as I don’t have whitworth tap/die. Not ideal for the yoke but could also probably find/make a replacement with relative ease if there is not enough thread/metal in existing one to retap.

Drive shaft needs to shorten by 6 inches, can I simply cut the existing one? I have read on the forum that later shafts can have hardened ends etc which I assume I wouldn’t want to completely
remove, but not sure if the 170 falls into this category or if there are any other issues cutting this shaft. If cutting 6” off isn’t a good idea, I can’t seem to find a standard shaft 170 replacement. But would a standard kingfisher/osprey shaft fit the crank/pinion sleeve? Looks like I would only have to take 1/8” off of one of those and they’re more readily available.

For the drive shaft casing, converting existing one definitely not easy or economical for me. So wondering if there are substitutes from other models that would fit without modification? Perhaps EFNR? I would need it to be about 17.25” give or take a bit, I can always adapt first 5 items to fit the shaft casing if it’s close enough to what I’m hoping for.

Thanks for the feedback.
User avatar
Charles uk
Posts: 4871
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: 170 conversion long to standard shaft

Post by Charles uk »

Would it be easier to bolt a plank of wood to your transom, to raise it's height the required amount?

That will take an hour & it's adjustable, if you need to change it.
Make it idiot proof and someone will make a better idiot.
andrew
Site Admin
Posts: 116
Joined: Wed May 24, 2017 5:37 pm
Location: ..

Re: 170 conversion long to standard shaft

Post by andrew »

Modifying the boat is not possible in this case, or I would have gone that route to start with. Any thoughts on the drive shaft and casing questions?
Horsley-Anarak
Posts: 2838
Joined: Thu Aug 07, 2008 8:42 pm
Location: Surrey

Re: 170 conversion long to standard shaft

Post by Horsley-Anarak »

04022009065.jpg
I just cut the same amount off everything, only issue is if drive tube has a reduced diameter where it goes into gearbox, cant remember on 170.

Did wonder if drive shaft was hardened, you could always case harden it, but I did not bother.
You do not have the required permissions to view the files attached to this post.
User avatar
Charles uk
Posts: 4871
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: 170 conversion long to standard shaft

Post by Charles uk »

Yes your right H-A, all the 170's have the thicker walled drive shaft tubes that have a reduced section at the top & bottom to allow the continued use of the model 90 transom bracket & water pump housing, they had to use the bigger diameter tube to stop them bending under the factory claimed 170 lbs of thrust, that was part of the reason that the rubber thrust cushion was used on the drive shaft tube, it removed the hard corner where they bend when it was put in gear at too high revs, when they bend you can hear the corners of the drive shaft hitting the inside of the drive shaft tube.

Unhardened end drive shafts, tend to get very tight on the square drive ends on the crank shaft & the pinion gear!

That was the reason I suggested raising the motor, if you can't lift it, run it deeper if there's enough water.
Make it idiot proof and someone will make a better idiot.
andrew
Site Admin
Posts: 116
Joined: Wed May 24, 2017 5:37 pm
Location: ..

Re: 170 conversion long to standard shaft

Post by andrew »

Yes thanks guys. The reduced diameter at the end is what has me looking for a potential replacement instead of shortening the shaft tube.

If the reductions are meant to handle the model 90 bracket and gearbox, do you think the 90 shaft casing tube would fit on the cylinder/tray end of a 170? I’ve not got one to try. Only thing I can think is that the cylinder studs would need to be the right spacing, otherwise the shaft tube top end looks ‘normal’ to me . And if the 90 shaft length is slightly different to the 170 I can cut the rest to size, I think it would be close enough.

If I do have to cut the existing shaft tube and get it turned down at the end, is the main part of the tube thick enough for this? Sounds like it could be based on Charles’ description.
Post Reply