TOPIC: Vid of 1961 Merc 800 running a 23" 3 blade Al prop

I want to give an update on my set up (work in progress) to those interested and would gladly accept any and all critiques or advice.

I mentioned in my other post that I raised the motor 5/8". Here is a video of the 23" pitch prop at that new height. Got a little faster than last time.

The boat settles down at about 47mph. Still trying to figure out the tach (you can hear me call out rpm numbers periodically).

Thank you for looking,

Pete

I'll leave the advice giving to those guys who really know what they're talking about, just wanted to say thanks for taking us along for the ride.

motor sound higher than 4000 RPM's get conformation on the tach first.

I'd say more than 4000, but still under 5500..(just guessing here).

Saw the S+F post too. Did it run through the hopping now?

Hi Mark,

Thanks for looking and your welcome

Pete

dave bernard wrote:

motor sound higher than 4000 RPM's get conformation on the tach first.

Hi Dave,

I agree it does sound higher that 4000. I put a new rectifier on last night(thanks Dr. Frankenmerc!) and I'll take it out to test this week, hopefully.
Crunch the numbers for that prop and say 10-15% slip and it should be 5200-5400 or so.

Pete

Robby321 wrote:

I'd say more than 400o, but still under 5500..(just guessing here).

Saw the S+F post too. Did it run through the hopping now?

Hi Robby,

Yeah, I posted over there (and here) to see if there were any techniques to get through that bouncing stage faster. Should of done a thorough search there first, as it seems to be common to have a mid-range bounce while trying to air out the boat. Pretty slow boat for S&F, but I figure couldn't hurt to ask

I did get through it in the video at about 47mph, it just smoothed out at went, then I slowed down and it came back.

There's enough angle to tuck the motor in enough to get rid of it, it only shows up when really trimming out.

Pete

Thanks for posting the video. That's a great sounding motor!

You are getting there. Try a 21 incher and get the revs up. Engine does sound like it is lugging somewhat.

The bouncing/hopping is the boat trying to get fully "on the pad". You want the bow to be slightly up with the engine at neutral trim, as in having the cavitation plate running as close to level with the lake surface as possible. This gives maximum engine thrust to achieve the fastest speed. Setback and weight shift are the methods to get ideal setup. Once you figure out the lowes and highest speeds where the hopping occurs you can try minor setup tweaks to narrow the range a bit. On the negative side, it means lots of testing. On the plus side, testing means water time. Keep us informed, and if possible, have someone on shore take a pic of the boat at speed. Trim angles felt in the boat can be deceptive, so a shore shot can be revealing. Happy boating.

Thanks VinTinFan!

Pete

Very good advice, I do have a 21" and I'll give that a try. It's a 2 blade, so I was hesitant to try it.

Pete

Hi Kerry, thanks for the info!

I'll try to get a shot of the boat.

A lot of weight in the stern, motor, tilt/trim unit, 12 gal. gas tank and driver. Battery is up front.

As long as more water time is involved, I'll test for years

Pete

Are you kidding me? Water testing is what we live for, straining for that perfect setup, and more time on the water is what we all want in the end. To misquote Steve McQween "Water testing is life, all the rest is just waiting around."

Remember that Mercs love to rev, and you will not get the full rated horsepower out of that engine until you can achieve redline at WOT. I think a 21 will awaken the beast, and give you a better holeshot to boot. Don't be afraid of the two bladers, I have them on all my engines.

Yep on the 2B as run one too! Tried a 3B 12x24 from Doc, and way too much torque steer! Flatty loves the 12x24 Cupped.

Robby321 wrote:

Yep on the 2B as run one too! Tried a 3B 12x24 from Doc, and way too much torque steer! Flatty loves the 12x24 Cupped.

Now THAT is a prop! I didn't realize you could use such small hub props on through hub exhaust motors, very cool!

Pete

peter1708 wrote:

Robby321 wrote:

Yep on the 2B as run one too! Tried a 3B 12x24 from Doc, and way too much torque steer! Flatty loves the 12x24 Cupped.

Now THAT is a prop! I didn't realize you could use such small hub props on through hub exhaust motors, very cool!

Pete

No problem for me (had a 14x28 on my XS also). Actually on a full throttle punch lets the motor spin up to 3000, grabs and 2500, and away we go! Or ya can feather it for grab lower throttle.

I ran the numbers. Id say your turning 5000-5100RPM and thats about what Id say it sounds like too. I use .09 for slip as a baseline for the calculator most of the time.

21 pitch would probably be pretty good. and get you into the 5500-5600 where that motor will be a bit happier.

A good 2 blade brass prop will be nice.

But modern 3 blade props like Laser II's and Choppers will out perform the old brass most days of the week.

Aluminum usually does not do well for speed runs. Test as many props as you can get your hands on. A 20 or 22 chopper. Or Laser II would be nice .

If you have a water pressure gauge start raising the motor up as well.
Nice rig,
Conrad