Need new prop. No Tachometer

[mercurymang]

My prop is not in very good shape and I need to get a new one. However, i have no tachometer on my boat so i cant tell how my current one is performing. Should I just get what is called for by Mecury or do I need to do all the analysis before i buy a new one?

 

[Georgesalmon]

Re: Need new prop. No Tachometer

I guess if everything was fine you could just get the same prop you already have or even better have the one you have rebuilt by a prop shop. But, if you want to know for sure everything is right you HAVE to know things such as the WOT rpm and speed. However if the prop you have is bad then you can't use it for the info you need in its present condition. Get it rebuilt and then get the information.

 

[RogersJetboat454]

Re: Need new prop. No Tachometer

My prop is not in very good shape and I need to get a new one. However, i have no tachometer on my boat so i cant tell how my current one is performing. Should I just get what is called for by Mecury or do I need to do all the analysis before i buy a new one?

Every engine and boat combination is different. Even the manufacturer of the boat can't tell you the best prop to use, let alone Mercury who's engines go on the back of thousands of different hulls. The only thing qualified to answer your question with the best results is your engine. Get your self a tach. Get your current prop repaired, and see where you stand. If the current prop keeps the engine in it's correct WOT range, then keep it on. If it falls short, or over-revs, keep the repaired prop as a spare, and get your self the correct prop.

 

[mercurymang]

Re: Need new prop. No Tachometer

Ok, thanks. I'm going to install a tach. Any recommendations?

Also, can a prop be repaired if it's missing metal?

 

[Georgesalmon]

Re: Need new prop. No Tachometer

If you just want a tach just for testing get a tiny tach. If you want one to install in your boat go to Faria, Teleflex, or any other brand that you like the looks of. All the marine tach manufacturers will have a chart o their website that tells which ones will work on you motor. Iboats has tachs right here that will work fine too.

 

[QC]

Re: Need new prop. No Tachometer

Here's what you need to do:

1) Have it repaired, yes even with missing metal.

2) Get a tach.

3) Test with repaired prop (you have to start somewhere)

4) Buy a new prop based on your test results and desired performance changes if any.

You need a spare anyway, so if the repaired tach (oops: Prop) is off some, so what? If the new one doesn't perform as well as the repaired one, then the new one becomes the spare. Ether way you have more data, and a spare prop.

 

[mercurymang]

Re: Need new prop. No Tachometer

Ok, thanks QC. I'll report back when I have done all this.

 

[HeloMech]

Re: Need new prop. No Tachometer

What's it cost to get a prop repaired, as a basic guideline. I mean, if a prop new is only $110 plus $40 for a hub, is it worth it? Ps, yes, I know that's a very basic prop. Not a race prop, SS prop, dual prop, etc.

 

[jestor68]

Re: Need new prop. No Tachometer

That depends on whether( not in my case) you have a good "prop shop" available.

The only one around these parts isn't the best, so I don't bother paying them 20-50 bucks to "repair" a prop anymore. They always seemed to vibrate when they get through with them.

Rather than risk damaging the lower unit, I advise folks to just buy a new one, especially if it's a reasonably priced aluminum prop.

 

[mercurymang]

Re: Need new prop. No Tachometer

That depends on whether( not in my case) you have a good "prop shop" available.

The only one around these parts isn't the best, so I don't bother paying them 20-50 bucks to "repair" a prop. They always seem to vibrate when they get through with them.

Rather than risk damaging the lower unit, I advise folks to just buy a new one, especially if it's a reasonably priced aluminum prop.

That leads to my next question. I'm seeing aluminum props one at the $80 price point and the other at the $120 price point. Any recommendations there?

 

[mercurymang]

Re: Need new prop. No Tachometer

bump

 

[QC]

Re: Need new prop. No Tachometer

On some boats the $80 example may beat out the 120 and visa versa. You can't know without testing. Just the way it is . . .

 

[mercurymang]

Re: Need new prop. No Tachometer

But what is the technical difference between the two?

 

[QC]

Re: Need new prop. No Tachometer

Clickable links to examples?

 

[mercurymang]

Re: Need new prop. No Tachometer

Here is the result page I get when I search for 65hp Merc 650, 12"pitch

http://boatpropellers.iboats.com/Mercury-Outboard-Propellers/?pitch=12.00&chart=51&engine_id=262&*******=558074140

 

[jestor68]

Re: Need new prop. No Tachometer

Well, we finally found out what motor he has; by default.

 

[QC]

Re: Need new prop. No Tachometer

Yeah, I thought maybe a 25 4 stroke for some reason.

To MercMang,

The fact is that none of us can really tell you if either of those will be better or worse. There is a significant portion of prop technology that is almost dumb luck. I call it Voodoo. Of course there are some that know a lot more than others, but even they will say that results are the only thing you can rely on. A four blade may work well, the larger diameter is usually indicated on a heavier combo, SS is almost always faster, but that brings in additional variables. I think you need to pick one and go, but AFTER you get better data with either a repair or some other prop. If you are not going to repair, buy the cheapest one, and let's start there.

 

[mercurymang]

Re: Need new prop. No Tachometer

Ok, sorry. I guess I'm frustrating you guys. I'm new to the boating thing and just trying to understand it all. I'm ready to buy a prop but only wanted to know the difference in the $90 and $130 version.

 

[QC]

Re: Need new prop. No Tachometer

Ok, sorry. I guess I'm frustrating you guys.

Don't worry, we'll get over it. Every single bit of info is helpful. It's kind of like someone asking us what tires for a Chevy engine . . . OK, truck? Car? Econobox? Lug pattern? But worse . . . water is squishy, and asphalt is not, so blade shape, hull shape, diameter, speeds, use, weight, material all come into play, plus about 4000 other variables.

I usually say: mo info = mo betta answer. In your case the missing bits are current data and boat/engine info. And there is no real answer to the question of which one is better because on my boat the 120 example may work and on your boat the 80 example may work, and work significantly better. The longer portion of my reply holds true. Hang in there, we'll help you get it right.

 

[mercurymang]

Re: Need new prop. No Tachometer

What I have is a 74 EbbTide with a 650 merc. I thing the boat is under 1000 lbs. The prop that is on there currently is a 46 61816A4 12P. The only thing I know is that it is 12" pitch. I will probably just match that prop although i'm not 100% sure that it's what came with the motor. However, as you say, it's voodoo. I need to get a tach so I can determine my rpm. I bought a merc manual and need to determine what the recommended cruise rpm is but havent found it yet.
Right now, my dilemma is do whether or not i should go through all the steps of trying to determine the perfect prop or just go with what the site recommends?