TOPIC: Inline 6 Prop Fitament- Have Part Numbers

I need a prop for my 76 Merc 1150 Inline 6.

There is a prop on it, that is in bad shape.
Mercury
48 77344 A4 17Pitch (13-1/4"x17)

There is a guy on C.L. that has a prop for sale
4877348 A45 21P (12-3/4"x21)

Will it fit??? Thanks

That 21" pitch prop would fit your motor, and would be ok for a lighter boat but I have a feeling it's not gonna push your 18' very well.

More than likely the 17" pitch that's currently installed is the correct prop for the application.

These old Inlines like to wind-up, and if you don't prop the motor for a full-throttle speed of around 5500 rpm with the boat lighly-loaded, it'll be too much load on the motor and can cause piston damage from detonation.

If the 17" prop still has all its blades and they're just chewed-up, it can be reconditioned at a prop repair facility for about half the price of a new one.

Otherwise, I'd recommend eBay or just keep searching on Craigslist and I bet you'd eventually find one. It's likely you could find the right sized prop on a 4-cyl 800/850/85/80/75 as that prop size is very commonly used.

Note that when you're looking, V6 props appear to be almost like an Inline prop, and have the same number of propshaft splines, but the V6 hubs are of larger diameter (except for the hi-performance gearcases if I recall correctly). The larger-hubbed props won't fit an inline gearcase.

Prop diameters are larger as well, anything above 14" won't fit the inline gearcase, either.

Inlines don't like to swing large-diameter props in any case, a 13-1/2" to 13-3/4" dia is normally the largest you'll see for any of the inlines.

The 12-3/4" X 21P prop will spin up nicely and push a light boat to fast speeds, but will bog that inline down when run on a heavier boat.

HTH & G'luck......ed

Thanks bud. I haven't had a chance to test the motor or the boat for that matter yet. It will be taking its maiden splash this summer.

I've gathered from my other sidewinder pals that they are either running a 21p or 19p with an inline.

Whats a fair bargain for a used prop (guy says its new in the box). If the price is right, I'll pick it up anyway.

Thanks for the tips, and yes I am aware of the 4 1/4" Gearcase on the inlines. I just don't know whats interchangable and how to know if the prop has the correct gearcase size.

Seems as everyone is telling me to stay away from the 21P.
ANYONE GOT A 19P to sell? It can be aluminum, I just need something to replace the chewed up 17P on there now...