18' Classic - What Pitch/Dia Prop Do I Need?

[Rich Maas]

Just went to the Toronto boat show yesterday and I now realize that the next 4 months is going to kill me while my boat is in storage.

I've got an 1987 18' 2+3 with a stainless cleaver prop (at least I think it is a cleaver). The prop has no pitch/dia numbers on it from what I can tell (or I might be blind). Since I boat on a rocky lake I'd like to pick up an aluminum prop. Can anybody tell me what pitch/diameter I should be buying for max performance that won't hurt the outdrive? My engine is a chev 350 with an alpha 1 (typical set up).

[BERTRAM BOY]

A 14X21 would probably be a good place to start. Assuming that you have a 260 hp 350.

BERTRAM BOY :D :D :D

[Ranman]

Max performance = stainless
Less than max = aluminum

If you have the 260hp motor and a 1.5:1 Alpha, Cliff is right with the 14 x 21.

If you have more like 300hp (new 350Mag) and a 1.5:1 Alpha, you should look for a 23P Mirage Plus (dunno dia.) Problem is Mirage Plus is a SS prop. I can't tell you if there is an aluminum equivalent.

Also, search this site on "props"...Lots of great info. Many folks here with 18 Classics have has success with Turbo props from Precision Propellors. www.turbo-props.com. (http://www.turbo-props.com.) Again, these are all SS props.

Final note: You should be able to find the ratio of your Alpha drive on a sticker on the side of the drive.

[Rootsy]

the 1987 350 mag was 270 pshp... the regular motor was 260... i know from experience that the mag will turn a 21 cleaver about 4800 - 5000 rpm full trim...

[JWCall]

I'm lookin for a new prop too and i was wondering how the 4 blade SS props are for a 1968 18' classic with a 351W and a volvo outdrive that i believe has a 1:3 ratio and what kind of pitch/diameter are good to go with.
THANKS

[Barry Phillips]

Hi Rich, I have a 98 Classic 18 with a carburated 350 making 250 hp. I am running a Bravo 1 drive, 1.5.1 gears with a 23" Veangence SS wheel. The boat will run 65.2 mph with 2 aboard and about 30 gallons of fuel. I have seen 66 mph under the same conditions in cool fall weather and 2ft chop. I tried a 21" Mirage Plus and gained 200 rpm but lost 3mph. The 65.2 mph is confirmed. With little fluel and just myself, I have seen 67-68 mph on the speedo.

SO-SLO