Mercury 75hp PROP HELP!!!!!!!!!!!!!!

[luke.belcher]

I have a '99 Pro Team 175 Special Edition Bass Tracker. It's a 18' aluminum boat. I has a Tacker Marine by Mercury 75hp outboard on it that came with the boat new. The motor as a Aluminum 3 blade prop that has bent blades, hince the question. WHAT PROP IS A UPGRADE FOR THIS MOTOR AND BOAT FOR TOP END SPEED????

The prop with the motor is a Aluminum 3 blade prop with the following numbers on it ( 48 - 77348 - 445 - 21P.

I'm looking for a stainless steel upgrade prop for top speed for the boat.

With the current prop with a 21 pitch, before the blade was bent, performed perfectly. Was great to get on plane and had great holeshot. Top speed with one person was 42-45mph at 5,000-5,500 rpm. Even with the same gear and four people, the boat did not suffer much. Plained good, and would still run wide open throttle at 5,000-5,500rpm but top speed wasn't as much as with one person obviously.

I contacted bass pro shops on this issue also, they gave me the following as replacement props:
Diameter/Pitch Item number
13-1/4 x 15 38-524-310-53
13-1/4 x 17 38-524-310-54
13-1/4 x 19 38-524-310-55
13-1/4 x 21 38-524-310-56
13-1/4 x 23 38-524-310-58


So, any help on prop upgrades would be great guys. Thanks

 

[Barnacle_Bill]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

That 21 pitch is perfect for your boat.

 

[duknut51]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

I would look at these and not in this order. This order is more in line of cupping. The first two are lightly cupped and the last two have more and might be a little harder to turn than your aluminum.
powertech eld3
mercury vengeance
powertech red3
stilleto
Been doing a lot of research on this subject for my boat and just my opinion.

 

[luke.belcher]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

I saw that the cupping has a lot of advantages. Any advantages for a 18' aluminum boat? and any advantages over the stands 13 1/4" 21P aluminum prop thats on the outboard?

 

[Dhadley]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

A ss prop is capable of holding a much more complex shape than the aluminum. The right ss prop will have more lift therefore reducing drag and increasing efficiency which in turn means more top speed.

 

[luke.belcher]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

so for the size boat and motor, what Stainless Steel Prop would be good? Cupped or slightly cupped or standard blades? what pitch and diameter? a friend suggested Turbo used to make a prop called a lightening Jr, that was designed for motors like mine. He said a friend of his had one. 13 1/2 x 20 pitch. Does the extra 1/4" diameter help or hinder? And does that with a 20 pitch any better than the 21 pitch i'm currently using? I know lesser pitch means not as much top speed, but he said these props were great all around and fast. Any ideas? looking for top speed out of the boat and prop. the current pitch preforms great and hits the top rpm ranges with one to 4 people and a load no problem.

 

[duknut51]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

My experience was a 3 mph gain going from a 19p yamaha aluminum to a 18p vengeance. The yamaha aluminum wasnt a good choice for my setup. I have a 18' boat with a 90hp yamaha. I looked at your prop slip and it looks like your aluminum prop was doing very well or so I think. I wouldnt get too carried away with cup. I wouldnt think your setup will need a lot of bow lift that a higher rake and cupped prop has and they are harder to turn or get your rpms unless you raise your engine on the transom then those props have better bite. I hate to say on pitch. If your buy a 21p and loose 100 or 200 rpm and gain in the slip area it may just even out. Diameter may cost or gain you 50 rpm or so depending on which way you go. Yet i understand a 1/4" has a little more blade and bite. I have heard that the turbo you mentioned is a good choice in this situation. Its a tough decision and at twice the money you dont want too mess up. If you could borrow or try one from someone you would know for sure

 

[luke.belcher]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

So if I went with the 13 1/2 x 20 pitch turbo lightning jr. prop that was recommended. I know the higher I lift the motor up the better the outboard will perform. Could I re-mount the motor to the transom on the outboards lowest mounting holes (meaning the outboard will sit higher on the transom)???

 

[Silvertip]

Re: Mercury 75hp PROP HELP!!!!!!!!!!!!!!

You raise the motor one hole at a time and test noting top speed and engine rpm while experimenting with trim settings. If you get to the point where engine rpm goes up but speed doesn't or drops slightly you know you've gone too high. You must also be careful that you don't go so high that you lose water pressure -- meaning the water inlet ports on the lower unit no longer provide cooling water for the water pump. When trying to optimize a setup to extract every last bit of performance it is suggested you install a water pressure gauge.

Also be aware that 1/4 inch of diameter does not mean the prop has more blade area. Within the same series of prop you will likely see a small diameter difference from one pitch to another. As pitch goes up diameter tends to come down a tad and vice-versa. It is called prop design. Diameter and pitch are only two characteristics. Rake, cupping, blade shape, blade thickness and prop finish, are just a few more.