prop

[nob]

oh god i think i've cocked up i've just been looking at my prop, like you do, and it looks kinda small compared to my mates! my engine is a 1993 merc 50hp 2 stroke but it came off a 19ft orkney longliner so is the prop going to be ok on a 4m searider, my mates boat is 4.5 mtr with a 40 hp evinrude 2 stroke and the prop looks bigger, - what sort of size should i be looking at on the searider: sorry for all the questions but i haven't put it in the water yet and dont want the motor to over rev or do anything else horrible if getting the right prop will stop this, many thanks, nob

[mister p]

try it first

[nob]

yeah you're right but how will i know if its over revving, is it just by sound/feel?

[kerny]

Originally Posted by nob

oh god i think i've cocked up i've just been looking at my prop, like you do, and it looks kinda small compared to my mates! many thanks, nob

Well I never... looking at your "handle" I would have thought that it would be much bigger than yer mates nob.

[nob]

well yeah, obviously, but we're talking props here honest

[Downhilldai]

You probably need a 14" or 15" pitch prop with that motor on an SR4. It may have been propped wrongly for the Orkney, so don't assume anything.

Your mate's Ermintrood has a lower ratio gearbox, so will naturally run a higher pitch prop than your Merc.

[nob]

cheers downhill, roughly what would that measure across the face of the prop, i cant see any markings on it ?

[kerny]

Originally Posted by nob

well yeah, obviously, but we're talking props here honest

I believe you honest

[mister p]

Originally Posted by nob

yeah you're right but how will i know if its over revving, is it just by sound/feel?

Chances are you'll experience emptiness towards the end of your throttle travel, a bit like "blowing in the wind".........much ado about nothing. ( simply put the prop is too small )
The opp side to this is the engine throbbing and sounding "gluggy" and taking an age to spin up. ( in simple terms the prop is too big here )
However it's not a size thing........there is pitch, diameter and slip.
Not an easy thing to work out even for experienced users. You need a prop specialist. Cheapest way out, if you find the right guy/gall.

[nob]

oh bugger, now i've got to ask his missus whos is biggest

[mister p]

Originally Posted by nob

oh bugger, now i've got to ask his missus whos is biggest

"Suck it and see", in other words.

[kerny]

Originally Posted by mister p

"Suck it and see"

Not a Fisherman's Friend I hope

[nob]

cheers mister p, hopefully launching at the weekend weather permitting so i'll just have to see what happens. (no sucking involved )

[mister p]

just blowing

[Downhilldai]

Don't get too embroiled in variables other than pitch for a 50 Merc. The diameter should be around 10.5", some are 10.125", some are 10.625".

Get the pitch right with a standard spec Merc/Quicksilver prop and you'll be fine.

The prop dimension will either be cast into the heel of one of the blades, near the hub, or on the forward face of the hub centre, where it bears on the thrust washer.

15" pitch prop for Merc 50:

[mister p]

Indeed, you could get embroiled but you don't need to.

[nob]

awesome, the prop seems to be just over 10" so i'm gonna chill and just get on with using it!! cheers downhill and everyone, just hope the weathers good for the weekend

[Pikey Dave]

Don't get hung up on the diameter too much. Its the effective length, not the width that matters. Though some of us have both