Prop help for Mercury 850

[scottrbishop]

I have a 15' Glastron GT150 with a 1973 Mercury 850 that needs a new prop after I discovered a shallow spot on a local lake. The boat weighs 850 lbs. and the motor 250 lbs., and I am trying to pull a slalom skier with 450 lbs. of weight in the boat, so we have about 1600 lbs. total weight. The problem is that my tach isn't very accurate, the engine has great compression, just did a carb cleaning, new plugs, and a SeaFoam engine treatment, but it still reads around 3,000 rpm's at WOT (which I know can't be correct.) The boat is also too old to have a speedometer, so I know the vitals here are missing. In short, the engine is working fine with the 19" pitch I have on there, and I beleive this pitch is best for skiing applications? Unless advised otherwise I'll pick up another 19" pitch, so my question is whether to do aluminum or SS? I read another post here that cautioned an SS prop due to a possible lower unit problem? If someone could shed some light on this subject for me I would really appreciate it, I don't know much about boating but I love to ski and just want to chose the one prop that will give me the best results for acceleration with 1600 lbs. of weight. Many thanks,

-Scott

 

[WillyBWright]

Re: Prop help for Mercury 850

Stick with aluminum. Most stainless props are ventilated and that doesn't work well at all for towing. Although many offer plugs. They are also very hard on gears should you find that shallow spot again.

 

[scottrbishop]

Re: Prop help for Mercury 850

Thanks for the help! Sorry, but I'm unclear as to what a ventilated prop is as oppose to a non ventilated prop? Again, thanks for the advice!