longshaft?

grahamcamm · Post by **grahamcamm** » Sun Jun 21, 2009 6:22 pm

Did seagulls ever have such a thing as an extra long shaft? I've just replaced my old engine and being short of cash at the moment got a seagull. My old engine was a longshaft so got a longshaft in the seagull, however, with the other engine I could leave it on the transom whilst on the trailer and travel with it completely down and still have 6 inch clearance off the road but with the seagull the skeg touches the floor even before the engine is fully lowered. My boat is a cathedral hull and the transom is 20 inches.

Vic · Post by **Vic** » Sun Jun 21, 2009 9:19 pm

To fit a 25" transom, no not as far as i am aware

Your Silver Century Plus model is very deep from the top flange on the gearbox to the tip of the skeg, that's what makes it seem very long

The 40plus, Century 100 and Silver Century models measure 10" approx. the Featherweight only 8". I'd guess yours is 12 or 13 "

niander · Post by **niander** » Sun Jun 21, 2009 9:33 pm

Its possible to cut them down!

so long as it separates

sparky · Post by **sparky** » Mon Jun 22, 2009 4:16 pm

niander wrote:Its possible to cut them down!
so long as it separates

When you say cut them down I assume you mean the exhaust and drive shaft and tube?

Horsley-Anarak · Post by **Horsley-Anarak** » Mon Jun 22, 2009 4:35 pm

It is quite easy to do, just cut the same amount off each bit.

I took 6" off a 102 long shaft, if it has a clutch you will need to re-thread the clutch rod 1/4 BSF.

Dont forget the bearing in the bottom of the drive tube.

H-A

Collector Inspector · Post by **Collector Inspector** » Mon Jun 22, 2009 5:18 pm

YEP!

Making short is like above. Easy way to go.

Making longer is another story.

Not that is what you want to do.

How many have wanted longer I wonder and how did they do it?

C.I.

Vic · Post by **Vic** » Mon Jun 22, 2009 5:34 pm

But if Grahamcamm's transom is 20" the longshaft model as it comes is the correct model.

Shorten it and he'll risk lifting the water pump above the W/L and so lose cooling!

In this context transom height means the height of the topedge of the mounting above the W/L

Horsley-Anarak · Post by **Horsley-Anarak** » Mon Jun 22, 2009 5:37 pm

He said it was dragging on the road whilst on the trailer.

I am sure he will be ok to chop a bit off.

H-A

Vic · Post by **Vic** » Mon Jun 22, 2009 5:57 pm

I am sure he will be ok to chop a bit off

But if the transom top is 20" above the water and he cuts much off he'll have the water pump out of the water! that'll be no good !

A better solution is to take it off the transom while trailing.

niander · Post by **niander** » Mon Jun 22, 2009 6:08 pm

probably yes!

sparky · Post by **sparky** » Mon Jun 22, 2009 6:11 pm

Horsley-Anarak wrote:It is quite easy to do, just cut the same amount off each bit.

I took 6" off a 102 long shaft, if it has a clutch you will need to re-thread the clutch rod 1/4 BSF.

Dont forget the bearing in the bottom of the drive tube.

H-A

Thanks for that.

40TPI · Post by **40TPI** » Mon Jun 22, 2009 8:24 pm

Think there might be a snaggette here...

Patient is a Silver Century Plus, yes?

Longshaft drive casings on Plus models are larger diameter over most of their length. Ends are reduced to diameter of a std shaft to enter the water pump housing and also the engine support lug.

Click to enlarge

The bottom...

The top...

If it is a longshaft plus, as Vic has posted, then unless you fancy turning the cut end down to fit the water pump housing you need to source another driveshaft casing tube from a standard motor.

As H-A says cutting the exhaust and drive shaft is easy peasy. Getting a straight cut on the exhaust is easy using a joiner's mitre saw.

And if your donor standard shaft didn't come from a clutch model it is a simple matter to drill and tap a hole for the stud...

Peter

ps the shiny longshaft pictured above is an un-used new old stock item which is in excellent condition, just a few small marks in the plating. If anybody has a std length shaft in similar condition they want to swap please PM me. I can then swap out the rusty 40+ plus shaft in the pictures above!

grahamcamm · Post by **grahamcamm** » Mon Jun 22, 2009 10:28 pm

Hmmmm, it's a funny one this. It seems to be all in the prop size in relation to the engine size. I've just roughly measured my mates evinrude 15hp longshaft. From transom to cavitation plate on both seagull and evinrude are roughly the same, however from cavitation plate to bottom of skeg there is 5 inches difference. The seagull has a far bigger diametre of prop to the evinrude 15hp, but the evinrude has a slightly bigger prop and skeg to my old 5hp. So there could be 6 or more inches difference from my old tohatsu to the silver century plus but it looks like it's all to do with the prop diametre as the transom to cavitation plate are similar. I guess I've answered my original question except why has my seagull got a far bigger prop to my old tohatsu but are both of similar hp ratings?

pistnbroke · Post by **pistnbroke** » Mon Jun 22, 2009 10:49 pm

The top of the cavitation plate should be level with the bottom of the hull.
there are three sizes in modern use
15 inch which actually is 17 inches from the cav plate to the top of the transom

20 inch long shaft which is often 21 or 21.5

and 25 in extra long shaft which is 25 in

You dont want the cav plate above the bottom of the hull or when you get on the plane ha ha joke joke the prop will come out the water ha ha...in this case you dont want the prop behind he transom or you spoil the water flow around the prop ....

Considering your prop you have four things diameter pitch and blade area as well as rpm these must match the output of the engine at wide open throttle....different combinations will match the engine ...eg 3 blade 10 pitch is equivalent to a 4 blade 8 pitch . Diameter has the least effect pitch the most .

timberman2004 · Post by **timberman2004** » Mon Jun 22, 2009 11:10 pm

Hmmmmmm.......

fundamental misunderstanding here ...unless I've got it all wrong

Seagulls designed for dispacement vessels ...= ... you'll NEVER get on the plane ....

our recent 3 day expedition down river was with the benefit of a lusty 102 SD, with a 2 blade 'thrust-a-matic' demon prop ..and no you don't get planing ...you can't

but you DO burble along very nicely, moving briskly, and attract loads of admiring onlookers ....which is seagulls all over as far as I'm concerned