1984 mercury 90 hp manufacturer recommendation for prop

[Blystone]

does anyone know what mercury recommends for a 1984 90 hp two stroke?

[WesNewell]

You can find out here. Just select a comparable newer engine.
https://www.mercurymarine.com/en/us/...or/#!/step-one

[Chris1956]

Inline six right? What size, type and weight boat is it going to be installed on?

[ahicks]

does anyone know what mercury recommends for a 1984 90 hp two stroke?

The right prop for that engine will depend totally on what kind of boat the engine is installed on. In other words, if that engine is on a pontoon boat, it will use a totally different prop if used on a runabout.

[jimmbo]

WOT range for that engine is 4500 - 5000. Engine makes its best power between 4700 - 4800 rpm Above 5000 rpm the power falls off rapidly due to small intake and exhaust ports and fewer reed valves than higher hp inline 6s. Great stump pulling bottom end though.

[jimmbo]

You can find out here. Just select a comparable newer engine.
https://www.mercurymarine.com/en/us/...or/#!/step-one

The newer engines have different RPM ranges and often different gear ratios, and since this selector doesn't go back to the era of the old inline 6s, any recommendation will most likely be incorrect

[WesNewell]

Well, without info on the boat he's going to use it on, it's his best bet for something close to accurate since he'll have to provide that info for the prop selector.

[jimmbo]

a 17” prop would work on 15 - 16 ft boats, a 15” on 17 - 18 ft. That’s based on 40 yrs propping those engines

[Blystone]

thank you to everyone who responded to my inquiry. sorry its a very very delayed response however my boat is a 17 foot fiberglass open bow 1987 monark 171 o/b

[Chris1956]

Gear ratio is 2::1. Prop is likely 15" Pitch, although final choice is by trial and error.

[WesNewell]

Do you know the dry weight of your boat? Under 1000# with 90 hp I'd try a 17-19p prop.