Prop Question

[FreeBeeTony]

A friend just gave me a prop from a Mercruiser I/O. Has a number stamped on it: 48-78120-19. Is this a 19" pitch? I have a '78 20' Grady Gulfstream w/ Mercruiser 165HP and 1.65:1 outdrive. Is this the right pitch? Is there a web site where I can check?<br /><br />Thanks.............

 

[Boatin Bob]

Re: Prop Question

Tony....what size is your current prop? What kind of RPM's do you pull at WOT, do you know what the recommended RPM's are for your engine. You need to know this before you go experimenting with another prop

 

[FreeBeeTony]

Re: Prop Question

Thats the problem, I just bought the boat w/o an outdrive and am rebuilding the engine. I know the ratio of the outdrive is correct for the boat but don't know where to start with a prop. I thought I once saw a web dite with a "prop calculator" you could estimate your prop size if you knew your engine/outdrive/boat weight.

 

[Boatin Bob]

Re: Prop Question

Sorry Tony..didn't realize you were starting from scratch, there are several sites out there that have prop calculators, here is one Propeller Calculator

 

[FreeBeeTony]

Re: Prop Question

Thanks Bob, that's what I was looking for.

 

[daveswaves]

Re: Prop Question

Hey FBT, the 19 is probably too agressive for your set up unless your boat is really light, and it does not sound like it is. If this is the 6 cyl chev 165 mercruiser, your max rpm is 4200 at WOT. On my boat, a 20 foot 76 Calglass with 165 HP mercruiser I run a 15" pitch prop with WOT at 4100, I have a 19 that I tried and the engine lugs down to 3500. This is no good for this engine. My boat is HEAVY and runs 32 MPH with either prop. I would look around for a 15 pitch and keep the 19 for a spare, it will still get you home in a pinch.

 

[FreeBeeTony]

Re: Prop Question

Thanks for the replies, now for another question:<br />Will a prop from an Alpha 1 drive fit a pre-alphe drive? The prop my friend gave me doesn't seem to go on tll the way.

 

[Bondo]

Re: Prop Question

Merc. prop shafts are All the same.....<br />You May be using the Wrong Thrust-hub...

 

[FreeBeeTony]

Re: Prop Question

Is the thrust hub inside the prop?

 

[codyandamber]

Re: Prop Question

its that big thick washer looking thing that seats behind your prop.

 

[FreeBeeTony]

Re: Prop Question

Even without that big washer, the prop willl not go on all the way!

 

[codyandamber]

Re: Prop Question

it should go on too far with no thrust washer on it at all.

 

[FreeBeeTony]

Re: Prop Question

Something is wrong then.......seems like the splines don't go back far enough on the shaft. I am confused!

 

[FreeBeeTony]

Re: Prop Question

bump

 

[FreeBeeTony]

Re: Prop Question

Am I missing something? It doesn't look like the splines are the problem but I don't see why it won't go on all the way. Anyone have any ideas?