Need new prop. No Tachometer

[QC]

Re: Need new prop. No Tachometer

I bought a merc manual and need to determine what the recommended cruise rpm is but havent found it yet

You won't. It's all speculation. Most think say something like 80% of the WOT RPM. The only way to really figure that out is with a fuel flow meter. You should read a bunch more threads here. That will help some, and I still think the answer to your biggest worry lies in the fact you need two props. Get one, and whatever it is it will serve two purposes: 1) Helps you select a better one and 2) becomes the spare if it is the lesser of the eventual 2.

Remember, if you whack anything at any speed, you're potentially dead for the day. If you aren't near your trailer, you are pretty much effed

 

[Maxz695]

Re: Need new prop. No Tachometer

I ran a 12 P on my V hul bass boat fiberglass )heavy and was getting about 4800 RPM to 5000. I tried a 13 P but it was taking a bit longer to get up on plane and running 4500 to 4800 RPM. I went as low as an 11P which ran 5200 to 5500 RPM. The 12 pitch for the weight and the WOT speed as well as planing abilities lied in the original 12 P prop. I have ran my 70 HP with a 14 P SS prop and was running 4800 to 5200 RPM at WOT and seemed to plne nice enough. Being your boat is 1000 lbs The 12 P would probably be OK see if it can get between 5000 to 5500 RPM with good quick planing abilities out of the holeshot. You may consider a 13 P due to the boat weight. If it gets up on pane quick it should give you 4800 to 5200 RPM with a good top end at WOT. as stated no one can be sure without testing but I would think that 12 P and 13 P are the way for you to go as you have a 65 HP Diamiter is an issue and I would keep the original diamiter you have as bigger diameter props tend to drag

 

[jestor68]

Re: Need new prop. No Tachometer

What is "a '74 ebbtide"? Is it 14ft, or 18ft? does it weight 600 lbs or 1600 lbs? Did ebbtide only make one boat?

 

[mercurymang]

Re: Need new prop. No Tachometer

What is "a '74 ebbtide"? Is it 14ft, or 18ft? does it weight 600 lbs or 1600 lbs? Did ebbtide only make one boat?

All I really know is that it's an Ebbtide branded boat that is roughtly 16' long, built in 1974.

 

[jestor68]

Re: Need new prop. No Tachometer

Something like this one? Note: borrowed from Shwamba.

 

[MH Hawker]

Re: Need new prop. No Tachometer

but only wanted to know the difference in the $90 and $130 version.

about 40 bucks

 

[mercurymang]

Re: Need new prop. No Tachometer

View attachment 172495 Something like this one? Note: borrowed from Shwamba.

that's the one.

 

[jestor68]

Re: Need new prop. No Tachometer

OK; now we're making headway.

As luck would have it, I bought(new) the very same(different brand name) boat with a 65 Mercury in 1974. It was the first boat I purchased new, off the show room floor. That is your classic 15-1/2 ft bow rider. That style was very popular for many years.

It came equipped with a 14 pitch, but I bought a 13 pitch to use for better ski pulling. I ended up leaving the 13" on there all the time because I liked the better all around performance.

I believe the motor's rpm range was 4800-5300 rpm. As I recall it would over speed slightly (like 5500 rpm) with just me in the boat with the 13", but with the family(4) in it, it would turn right there at 5200-5300 rpm.