Reprop for 2002 90 HP Mercury 2-stroke

[Boilerguy]

Anyone have any experience or suggestions for switching from an aluminum to ss prop on a 2002 Mercury 90HP Classic 2-stroke? I'm running it on a 2002 Nitro NX750DC. The manual suggests 5500 RPM and I see it running right around 44MPH at 5500RPM at WOT. I currently have a stock 3 blade aluminum, 12-3/4" @ 21 deg on it and would like to switch to ss. Mercury website is suggesting either a 13.25" @ 21 deg or 13.5" @ 22 deg. I don't have any real performance issues, but would just like to have the stronger ss prop and possibly pick up a few mph while maintaing the correct RPM.

 

[Texasmark]

Re: Reprop for 2002 90 HP Mercury 2-stroke

I have the exact engine, and year model. I am running a 24P SS Ballistic on a 17' alum boat BIA registered to 130 hp at 48 - 50 mph GPS. My rpm's are somewhere between 5600 and 5800 depending upon how much ventilation I am experiencing....i.e, like if I cut her back to 4500, go into a sharp turn, and goose it in the middle of the turn and come out just screaming...... The Ballistic is a hot dog conventional (I guess) prop.

Moving into SS will get you rake, thin blades and tip cupping. Rake pulls your bow up getting less wetted area and less drag/more mph......thin blades are analogus to slicing the water with a machette knife vs a Ted Williams bat in terms of thrust vs performance, tip cupping, grabs the water in the event you are near the surface with your prop (trimmed out, in a turn) and it grabs the water rather than let the water slip by.

44 mph is not that bad at 5500. I'd go with the 22P SS that you mentioned. The SS is higher pitched, which will load the engine more, lowering the rpm's but the efficiency of it will propell the boat faster relieving the load of the increased pitch......get the 22 and come back to me if nothing else on a PM>

Mark