Prop for 1994 90 2 Stroke, Selection 3 blade or 4 blade Question

[treeguyus]

Here are my questions. For a 90 hp Mercury 2 stroke 1994 Engine

1)RPM gauge recommended for proper prop selection any gauge better then others?

2)What brand type of prop do you recommend there are a number in each pitch?

3) Thoughts on a 4 blade prop for this engine.

Based on the boat a 1890 pro v tiller, loaded around 1900#'s 15 to 17 pitch prop is recommended.

Thanks for input always

 

[Texasmark]

Re: Prop for 1994 90 2 Stroke, Selection 3 blade or 4 blade Question

What engine? If a Merc the gear ratio is 2.33:1. If somebody elses who knows. Knowing this is important. 2 cycle engines like to run, they don't like to lug. Case in point, run a chain saw. Stick the blade in the wood before you rev it up. It loads up and quits. Conversely, rev it up to max rpms and then dig into the wood and it just eats it up. Same thing applies to a 2 cycle outboard engine.

You need to prop to run at the upper end of the recommended rpm range at WOT with a normal load. I run a little over. Never look back. I guarantee you that you need to heed what I say for max performance and minimum problems.

I like SS high rake for bow lift, ported for hole shot and cupped for max grab at the surface. Boat type has a lot to do with the prop. Operating in boulder or rocks does too. You ask a generic question. There is no generic answer. I gave you one but it is limited by the boat, engine, load, weather conditions, and environment. 4 blade is for really heavy loads. Does not give the best performance for lighter loads as 4 are less efficient than 3, 3 less efficient than 2 and you have to stop at 2 as you can't run a single bladed prop.....for very long.

Mark

 

[jestor68]

Re: Prop for 1994 90 2 Stroke, Selection 3 blade or 4 blade Question

The Mercury prop selector recommends the Mercury Laser II in a 20 or 21 pitch, based on 1600 lb dry weight, 500 lbs people/gear and 12 gallons of gas. The recommended 4 blade is the Trophy Plus 21 pitch. Of course, the aluminum 21 pitch is there as well.

The Quicksilver Light Speed is available here in 20 pitch.

Pickings are slim in the 20 pitch range, while all sorts of props are available in the 21 pitch range.