1964 Mercury 500 Propeller Questions

[Craig_Bay]

Hi there. Forgive me please if this winds on a bit. I have a couple of questions. At the moment, i have a '64 merc 500 short shaft on my 12' glen l tnt. I am using a 2 blade 17p brass 'record' (looks like a racing prop - thin blades and such) prop, 11 spline obviously. It seems to be running the correct rpms(5500 or so), according to my rudimentary tests with auto tachs from canadian tire. My question is, if I wanted some more speed, would moving to an SS propeller from this brass fellah do me any good, and would i lose significant speed if I got the the present prop cupped slightly for ease of getting up on plane in the higher trim settings (no power trim, would love one of those cmc thingmys, but i cant seem to get ahold of one in canada). Alright, ill stop there I suppose. All the best.
-Craig

 

[ddrieck]

Re: 1964 Mercury 500 Propeller Questions

Not sure if this will help bur here goes.
I had an old 78 Mercury 500 50 and changed from a 3 blade aluminum prop to a 4 blade composite prop. I lost some top end speed but could jump up on plane a lot faster.

Also, I sent you a PM concerning the tilt trim issue.

 

[steelespike]

Re: 1964 Mercury 500 Propeller Questions

You may be able to fine tune your setup.
Raise the motor on the transom to a point just before venting(cavitation)
becomes a problem.Just add 1/4" sticks to the top of the transom to hold the height and tighten clamps and test.Be sure it has a good grip.and pumps water.My 65 Merc 500 sits on an approximately 1" stick,on the back of my 57 18ft Crestliner.Been like that since new.Cupping would help prop hold its grip better and allow more height.It may knock off some rpm probably hold its speed.Just be sure the shop knows what its doing.You may be able to remove a little pitch and add the cup.They can probably tell you if that makes sense.Make it clear what your running there are different kinds of cupping.Your motor is rated for 5,500 to 5,800.In its day the 2 blade was the ultimate speed prop assuming it was designed for that and not just a 2 blade.
2 blade isn't as well suited for overall performance.

 

[Craig_Bay]

Re: 1964 Mercury 500 Propeller Questions

Thanks for the replys guys. I guess my question was, is stainless steel 3 blade better then brass 2 blade for top end? Any comments on this? Also, if i decide to go for the ss prop, is it possible to get 11 spline hub kits that will fit a modern ss prop? Thanks again.
-Craig

 

[steelespike]

Re: 1964 Mercury 500 Propeller Questions

All things being equal the 2 blade should be faster.With the time span
unless the 2 blade was pretty sofisticated I would think that a modern high tech 3 blade would be faster, There is a chance you could have a prop shop press your hub into a newer prop assuming the bore of a modern prop is similar.You might consult with the guys at Scream and fly they probably are
messing with props all the time.Don't know if they mess with little stuff or not.
of course you could ask a prop shop I'd be interested in their reply.
Your stainless Q :: not knowing the sofisticatrion of your present prop
and apparently you don't have the speed to go with your rpm to help
determine the props performance ability.I would say a new stainless would do better.Could improve a few tenths or a few mph.If your prop is doing awful then the improvement may be amazing. I was wondering if a modern prop shaft would fit an older motor.

 

[Craig_Bay]

Re: 1964 Mercury 500 Propeller Questions

Thats a good question about the prop shaft. That would be awesome. As far as performance goes, the boat is running 45mph (gps) with the brass two blade at 5500rpm. I feel like on a 12 foot plywood boat with the right prop, i should be able to see 50mph with this motor. Power trim will help of course. Working on that right now. I fear the old prop is pretty sophisticated. The blades on it are super thin and its a solid hub. I gather 'record' props were pretty highend back in the day. Anyway, im going to try to get it into a prop shop this weekend to see if they figure a Stainless 3 blade would be any better? Ill let you know.
-Craig

 

[steelespike]

Re: 1964 Mercury 500 Propeller Questions

Have you fine tuned the setup?At that speed an inch higher might add a mile or 2 top end.Also I've seen where they take a little cup out of a prop and gain rpm and speed. Gaining 5mph at that speed may be a trick but you never know.Aha The 64 is not a thru hub exhaust.That may complicate things
though I believe you can run a through hub on a non thru hub motor.
Assuming you can find the right spline count.
I was told My Merc 500 was a 65 but just noticed my aftermarket manual indicates 55-65 are non through hub.Now I may have to figure out what I've got.The guys at Johns Old Mercury Web Site may be able to help on a prop
suggestion /solution.Merc used to have a Special Quicksilver lower unit for racing.Don't know if any for a 64 and very expensive if available.
I think cheap would be $1,000.Not including the special prop.

 

[Craig_Bay]

Re: 1964 Mercury 500 Propeller Questions

Yea, 5mph may be a bit of a question mark. I think with a power trim unit i could pop motor up an inch or two higher then it is right now (cant now or it wont plane - the prop just spins) and maybe trim it out a bit more. I think thats going to be my focus first, then ill work on a new prop or lower unit. Getting one of those racing units would be incredible. Anyway, thanks for all the help. I appreciate it.
-Craig

 

[steelespike]

Re: 1964 Mercury 500 Propeller Questions

Good luck keep us posted.