Mercury 800 number help question

[DoctorCAD]

I called the Mercury 800 number to get some specs on my 1973 20HP Merc200. I wanted to know the RPM range and the stock prop size. The guy spent a lot of time with me and I'm grateful for his help. The only thing that was confusing to me was the RPM range he quoted me first was 4650 - 5500 and then he found a different range of 5000 - 5500. Which one is right? He suggested that I stay in the upper half of the range, but that would be 5075 - 5500 for the first range and 5250 - 5500 for the second range. <br /><br />Also, the prop that is installed is 10 x 11 (2) and he said that a 9 7/8 x 9 (3) was also available. Any opinions on which is better...the current prop has a few dingers and I want to replace it. I can get 23MPH with 2 guys and fishing gear in a 15' Starcraft and that is plenty fast, but I would like to get planed sooner to minimize wake for surrounding fishermen.

 

[mellowyellow]

Re: Mercury 800 number help question

I think 5000 is a good goal for RPM's, lower<br />pitch prop will have better hole shot, but u<br />may lose some top end speed.<br />good luck,<br />M.Y.

 

[DoctorCAD]

Re: Mercury 800 number help question

What about 3 blade vs. 2 blade?

 

[corm]

Re: Mercury 800 number help question

Hi,<br />You motor rpm is 4800-5500. The 11" prop is good up to 1000# total wt. The 3 blade 9" prop wt range is 850-1500#s. You will gain at least 300 RPM's with the prop change. If you change to the 3 blade you will get on plan faster and be able to stay on plan at a slower speed. The down side is that if you go out alone you may over rev your motor. In this case you may have to not run it at WOT. In the later yrs of production Merc sent the 9" 3blade as the STD prop for the 20HP, They felt that boats were heavier (flat floors & ped seats)with more toys on them like a ele troller/battery anchormates for & aft,ect. So after all that it is up to you to determine what your set up is like and what prop you will be happiest with. Your Dealer should be able to help some if he is on the ball. I personally would go with the 9" unless I had a bare bones boat. If it turned out to be to small I would get it piched up 1" in the winter at the local propshop to fine tune it.