Prop Questions

[QuarterHorse]

I'm not going to come on here and ask "What prop for my set up" rather I want to know what to look for when shopping for one. As of now I'll be using my '77 115 Tower of Power for my Vector. I'm under the assumption the small shaft is what I'm after?

When buying a prop I see you can have hub exiting exhaust props and non. I know on my motor there are the exhaust covers on the side I suppose I could un-cork, but what are the pros and cons between these two prop styles?

Chopper/Cleaver I think I have figured out that the chopper gives more bow lift where a cleaver gives more stern lift and is more so a drag prop correct? Other choices out there other than these would be?

I really appreciate the help, I just can't seem to get the right words/phrases in the search engine to get the answers I want.

-Dustin

[Streamin101]

I say a 26 small ear would be a good starting point if you are setup with a jackplate and lwp.

[David]

Small ear choppers were made for that motor and type of application. 24-26 seems right. If you keep the motor low, a lower pitch Laser, 20-22, would work great for all round use.

You need the small spline for that motor. Even pitch Lasers fit, small ear choppers fit. Big ear choppers won't fit, and the most common through hub props won't fit. Your gearcase is only 4.25", the common V6 gearcase is bigger. Most Trophys would fit, but I bet a Laser would work better.

[QuarterHorse]

I do have a 6" jack plate on the boat and had intended on calling Eagle One or Bob's Machine on getting a kit or possibly sending in my lower unit.

As far as thru hub props versus non, what would be the pro's/cons? I assume if I don't get a thru hub I need to un-cap the exhaust on the lower unit correct?

If I don't end up getting a LWP I had heard about filling in the top few holes of the stock water pick up to help aid in getting the motor up a little farther, almost sounds wrong but it's what I seem to remember hearing?

[rdkvector]

You can block off the top 3 holes if it has 8 to start with. You can take a 1/4 in drill bit and slowly turn it towards the front of the engine (good for another 1/2 pound of water pressure. A over the hub exhaust allows you to turn a bigger prop by letting it ventilate to help it spin up. A 22p small ear chopper would be what I would start with, easy to find and cheap. What is the gear ratio and is your motor prop rated or ph rated? Those are needed to determine what pitch to run. With small power, you need all the bowlift you can get and you'll get that in a chopper.

[QuarterHorse]

Motor is a '77, I assume it's not prop rated, it seems the Tower of Power was prop rated in '82 or '83?

I don't have any idea on the gear ratio, what numbers am I looking for on the motor and where can I go to find out once I do? I assume it's all stock.

Thanks for all the info

-Dustin

[David]

2:1, 115 at the crank. What's that, about 105 prop shaft HP?

My advice is to hold off on lower unit mods until you know its necessary. Certainly don't put a nose cone on if its not necessary. It could cost speed. Do get water pressure and water temperature gages.

[QuarterHorse]

Gauges are already in the boat. ;)

[Streamin101]

2:1, 115 at the crank. What's that, about 105 prop shaft HP?

My advice is to hold off on lower unit mods until you know its necessary. Certainly don't put a nose cone on if its not necessary. It could cost speed. Do get water pressure and water temperature gages.
:iagree: You will not need lwp untill you are going over 80, otherwise the cone is slowing you down.

[FlowMaxx]

:iagree: You will not need lwp untill you are going over 80, otherwise the cone is slowing you down.

Agreed :cheers:

[transomstand]

I'd get rid of the 6" plate.

[Streamin101]

I'd get rid of the 6" plate.
Why?, just curious.

[QuarterHorse]

I doubt I ditch the plate but I'd like to hear why. That's good news for my wallet on the low water pick up.

rdkvector - What do you mean about the 1/4" bit. Are you talking about opening up the other holes in the water pick up? As far as "going towards the front" can you elaborate?

Thanks all

Dustin

[transomstand]

Why?, just curious.

Low horsepower applications need a lot of positive trim to fly the boat. The plate takes away your ability to do that. Running at a neutral trim angle results in a too flat (and wet) angle of attack. We want a plate in a V-6 application to keep positive trim to a minimum, the additional speed will lift the boat on it's own.
Trying to use a V-6 setup with an inline produces dismal results, in my experience.

[Streamin101]

I disagree. You need the plate with low hp because the plate creates a better angle of leverage which is needed to pick the bow especialy on the vector. Positive trim is wasting horsepower you want the gearcase going through the water straight and level.

[transomstand]

I disagree.

Most people do:D

[QuarterHorse]

Guys I really appreciate the set up help.

As far as prop info goes, what other props are there to look at? This is going to be a general purpose boat, not sure if I want to sweat getting this motor way up in the air and getting it hot (even though I do have a gauge in the boat and could lower the boat back down) but don't want to buy a prop and sacrifice it not being correct and loosing bottom end.

I was originally thinking a 22 but other than a chopper what other options do I have? I have a friend with a plain jane Mirage 22 I believe I can borrow. Would a small ear chopper hurt my low end in comparison to a Mirage or are they just superior in all areas?

Also, what do I fill the top 3 holes in the water pick up with? Perhaps a link on a how to?

Thanks for all the info fellas

-Dustin

[rdkvector]

I would keep the plate with the low h.p. The drill bit opens up the hole a little, moving it towards the front changes the water flow angle. You do not want a nosecone, it will slow you down. A 22p chopper is all it will turn, I can't see it turning a bigger wheel. That is a ph rated motor, so it's about 100 hp at the prop. Properly set up, 55-58 is about the best you'll see.
You need the bowlift that a chopper will give you, stay away from regular round ear props. With a small motor, you need to the best possible set up, you don't have the power to compensate.
You can use regular bondo to fill the holes.

[transomstand]

This is how you go fast with an inline. Lots of positive trim to stick the nose in the air, which makes the prop shaft parallel to the surface of the water.
Take it for what it's worth. That's 80 mph in that photo.

http://i221.photobucket.com/albums/dd58/transomstand/viper.jpg

[QuarterHorse]

The drill bit opens up the hole a little, moving it towards the front changes the water flow angle.


Again, very sorry for asking the same question, but what hole?

[transomstand]

Again, very sorry for asking the same question, but what hole?

He's referring to the lower water intake holes in the lower unit.

[Streamin101]

This is how you go fast with an inline. Lots of positive trim to stick the nose in the air, which makes the prop shaft parallel to the surface of the water.
Take it for what it's worth. That's 80 mph in that photo.


You will get the same affect with the plate, and the pad will not be forced down on the water as much because the motor will be at level trim with the bow flying.

[QuarterHorse]

That is a ph rated motor, so it's about 100 hp at the prop. Properly set up, 55-58 is about the best you'll see.


The newer 115's make that much difference? I saw a guy posting on here in his Vector with an 83 runing 69.9 on his GPS. I was hoping to hit high 50's low 60's, 60 would tickle me pink with this motor, but I guess we'll see this spring. It'll have to do until I can get a 200 or bigger to hang off it.

Can somebody explain prop slip to me etc...?

[David]

You are pretty limited in your prop selection. The inline gearcase has a smaller diameter than the V6 gearcase. Mirage & Tempest won't fit. I don't think a big ear chopper will fit either. My old Merc accessory brochure says they won't fit.

Small ear choppers, even pitch Lasers, even pitch HighFives, and small hub Trophys will all fit. I've seen two attempts at Trophy's on small gearcase rigs, and in both cases they were lousy at planing. Actually one could not plane. Inline cleavers would also fit, but would not be a good choice for all round use, and maybe not at all with only 115 crankshaft HP

Used Lasers are cheap and perform well for all round use on a light V bottom.

Prop slip is the difference between the theoretical distance a propeller turns in each revolution and the actual forward motion. 27 years ago I could have explained the physics of why slip is necessary for forward motion, but not now. Is there a young engineer reading this?

Some slip is theoretically necessary. Too much slip is an indication that your set up is bad and more speed is possible.

I'd keep the jackplate. It makes it easier to adjust engine height, and it's already there. Only remove it if you can't resolve set up problems with it on.

[QuarterHorse]

Thank you David.

As far as filling the water pick up holes, Bondo doesn't seem like the correct thing to use when in every hull thread they say no bondo under the water line. I would have figured a two part epoxy of some sort? Any other input or advice for this?
Also wondering if the 15 HP difference would really kill my boat 10 mph as a later 115 powered Vector clicked off 69.9, not sure on the set up but I would hope I could hit 60. Any thoughts on that?

[Streamin101]

Epoxy would be better but waterproof bondo will do the trick also. I think 60 would be about max speed with setup, i ran a 73 115 V4 on my viking at 55 with it bolted right on the transom, full interior 23 sst.

[QuarterHorse]

Who's epoxy would you use? I don't have any "water proof" body filler so I've got to buy whatever I use.

Thanks all

Dustin

[Streamin101]

Anything should work just take the bond area down to bare metal and rough it up. Its all in the prep. If it falls off try sompthin else no biggie