Prop opportunity question

[fetoma]

Folks,

I have the opportunity to purchase a nice stainless 3 blade 13x17 prop for $50. I've got a 1987 V20 CC Steplift running a 1986 Johnson 140 that I just bought, so I don't have any RPM numbers yet. I believe it has a 13-7/8x17 on it now. What do you all think? Smaller diameter would mean what?

Thanks,
Frank

[THEFERMANATOR]

Does your 140 have the 4 inch or 4.5 inch exhaust housing? Those early loopers could be either one. If it has the larger 4.5", you MUST make certain it has the 2.25:1 gear ratio in it. The v-4 engines ran a unique 2.25:1 gear ratio in the lower unit when they came with the v6 4.5 inch gear case. The standard 1.86:1 v6 gear ratio will NEVER allow the engine to run properly(others have tried it, and they always ended up going out and finding a v4 lower to get the engine to perform and get on plane decent). If it has the correct 2.25:1 gear ratio with a 4.5" housing, a 17 pitch would be a good starting point. If it has the 4" with a 2:1, then you will need a 15 pitch. You must be certain that engine can spin up to 5600-6100 rpm's wot. I know the book says 5000-6000 rpm's, but I've played with them enough to assure you they need at leadt 5600(I propped mine to spin 6000-6100 for best power and economy, I saw drastic dropoffs by overpropping).

[fetoma]

Thanks ferm, lots to learn !!

[garbubba]

That being said, Buy the prop! That's a good deal & you could always trade up.