Clarification.

[Geoffrey Graydon]

Not really a question but I have often wondered why they always say ensure the Impeller key way is lined up fore and aft with the # piston at top dead center.I always do it but don't know why or what difference it makes,this is onefor you Racer.

 

[F_R]

I've wondered the same thing. Doesn't make a lick of sense to me. But a lot of stuff doesn't make sense to me.

 

[Fed]

I've never heard of it?
Maybe a rough way to make sure the flywheel key hasn't sheared.

 

[racerone]

You have to be clear with your question.------The impeller key / keyway has nothing to do with piston at TDC.-----Why are you asking this puzzling question ???

 

[oldboat1]

https://forums.iboats.com/forum/eng...boards/10869828-fd-11-points-with-multi-meter

TDC issue introduced by the OP himself. Maybe he can supply references for "they always say".

 

[boobie]

Edit.....

 

[Geoffrey Graydon]

You have to be clear with your question.------The impeller key / keyway has nothing to do with piston at TDC.-----Why are you asking this puzzling question ???

That would be my thought too but I have often seen it stated here and elsewhere and it never made any sense to me,I just wondered if any wiser heads than mine knew something I didn't.

 

[achris]

That would be my thought too but I have often seen it stated here and elsewhere and it never made any sense to me,I just wondered if any wiser heads than mine knew something I didn't.

Never heard of it. Please tell/show where you have seen it.

Sounds like a FE theory to me...

Chris...

 

[F_R]

I think it is in a service bulletin somewhere, but it would take me forever to find it.

 

[F_R]

OK, forever is here. Here ya go---

But it still doesn't make a lick of sense.

 

[jakedaawg]

I would guess that the shafts were breaking at the keyway... I bet they wanted to make sure the the power strokes were timed so the key was was fore and aft at that moment. Maybe if it was at 9 or 3 the shaft would flex a little they figured?

just mere speculation, no need to call me a fool...

 

[racerone]

The torque is transmitted through the shaft.-----I am not sure how they figured the position of the water pump key would matter.------Unless there was flexing of the exhaust housing at the same time.-----And yes parts under a load do bend / flex.----Hard to see by eye but they do flex.

 

[F_R]

Here it is repeated in the 1972 Factory Service Manual

 

[F_R]

I would guess that the shafts were breaking at the keyway... I bet they wanted to make sure the the power strokes were timed so the key was was fore and aft at that moment. Maybe if it was at 9 or 3 the shaft would flex a little they figured?

just mere speculation, no need to call me a fool...

Trying real hard to understand, and give the engineers some respect, I suspect jakeddaawg has hit upon it. I am thinking vibration is supposedly responsible for the breakage, and putting things in proper alignment times the vibrations to occur in or out of phase with weak spot at the keyway. Wonder why the shafts are "weak" after so many years of production with no problems.

 

[racerone]

Those 71 to 76 model 40 HP used the older style ( perhaps weaker ) exhaust housings.-----Not the same housing as the 1960 to 1970 models.

 

[F_R]

Well yes, but the housings were used on the 33hp and old 35hp. Yeah, I know, less horsepower and pin drive impeller Also used on Gale 40hp, but again with pin drive impeller. What tangled webs we weave, etc, etc.

 

[Geoffrey Graydon]

Wow,what a can of worms I opened ,at least I'm glad to see it was not a figment of my imagination.Stay safe all.