should I increase pitch to 13 on my 50 merc

[fisherguy123]

I took my new to me boat out the other day and it ran quite good . The boat is 14 ft Chrysler Valiant tri-hull....motor 1982 merc 50 hp....estimate boat and motor at 900 pds, 2 passengers 400pds ,gas 50pds, prop is quicksilver with 11 pitch.....was able to get 30.5 mph on gps. Don`t have a tach but motor sounded quite high in the revs....holeshot was great. Here is link to a video ...maybe someone with enough experience can tell by sound of it if I should increase the pitch.................. http://www.youtube.com/watch?v=eqFGW2uQtLo. ...........any help would be great
thanx

 

[steelespike]

Re: should I increase pitch to 13 on my 50 merc

Rpm is critical both for performance and motor health. Too many rpm will tear it apart too little will create premature repair problems.For about $50 you can get the latest Tinytach that covers most applications. With the tach you can determine what the rpm is and what pitch if any is needed then you can tell how well the change has worked.

 

[fisherguy123]

Re: should I increase pitch to 13 on my 50 merc

Rpm is critical both for performance and motor health. Too many rpm will tear it apart too little will create premature repair problems.For about $50 you can get the latest Tinytach that covers most applications. With the tach you can determine what the rpm is and what pitch if any is needed then you can tell how well the change has worked.

Yes I guess I`ll have to get myself one and check it out that way.......makes you wonder why the manufacture doesn`t install a tach on all outboards made.

 

[steelespike]

Re: should I increase pitch to 13 on my 50 merc

Yes I guess I`ll have to get myself one and check it out that way.......makes you wonder why the manufacture doesn`t install a tach on all outboards made.

They probably figure on a new setup the dealer will get it setup right.
If the owner doesn't start fiddling no need for a tach.
I think the old technology motors were a little more forgiving
with prop selection
Now we are running motors that run 1000 to 1500 rpm higher than some of the old technology.
And when we start fiddling we need to know how our results work out.
Of course a tach adds cost to a motor they may want to put in a cost package.



I

 

[sschefer]

Re: should I increase pitch to 13 on my 50 merc

Regarding why you motor doesn't have a tach. That's a good question. Steelspikes explanation is as good as any. Newer small motors have rev limiters on them which is befuddling in itself during prop selection. So the correct answer that was already said is that you do need a tach and all motors are capable of being setup with one type or another.

However, I must warn you, you are entering the world of prop voodo and you might just end up spending a lot of money spinning your wheels, (no pun intended). For reference, 1" of either pitch or diameter equals approximately 200 rpm. If you're running an aluminum prop be careful with the diameter, they do flex a lot. Stainless will be hard to find for that motor. I'm having a tough time finding the stainless prop that I want for my 2011 4 stroke 60hp Merc. I might have to go to pro's at Mazco to get one made for my setup.

Then there are 3 and 4 blade props for your motor. 4 blade props are nearer to a single blade than a 3 blade and therefore will almost always run with less vibration. Always drop and inch of pitch if you choose a 4 blade. 4 blade props almost always improve hole shots and tend to hold very well in the turns.

Off the shelf props are readily available but not all manufacturers are equal. There's some junk out there with big price tags so stick with the main stream stuff if you can. Quicksilver/Mercury has an excellent reputation, Solas is pretty good. Michigan Wheel is about mid grade in my book, they sort of stood still while the rest of the world passed them and are trying to play catch-up now. Stilleto's are nice, I liked their Bay Runner series. Just some ideas for you.

 

[fisherguy123]

Re: should I increase pitch to 13 on my 50 merc

"you are entering the world of prop voodo and you might just end up spending a lot of money spinning your wheels, (no pun intended)."

yes I can see that now after doing some research on the subject. I have another prop the previous owner had as a spare and although the pitch is less ...10.5....the diameter is about 1/2 inch larger and the blades are larger in width giving more square inches of grab in the water ......I surmise.....so this prop with less pitch may give me more thrust. It is in good condition so I will try it on my next trip to see what happens.