Update - New prop seems to slip a lot

[250Gimp]

Re: New prop seems to slip a lot

Re: New prop seems to slip a lot

Thanks again Craze1

I think I will order a 25p high five. Top end is not super important to me, but I don't want a friend or relative going over red line accidentally with the prop.

The next step up for the HIgh Five is a 25p, so assuming 5200rpm with the 23p, going to a 25p should bring me down near 4800rpm, which is where I want to be, correct?

Just a note that the main reason for changing is because the Bravo1 is a dog out of the hole on my boat, and we do a lot of water sports. (slalom, wake, tubing...)

CHeers

 

[craze1cars]

Re: Update - New prop seems to slip a lot

That makes sense to me on paper...

Even if you're revving a little high with the 25 pitch (up to 5,000-ish), you'll be good for watersports and it won't hurt that engine at all....as long as it's enough to keep it off the rev limiter I would expect you and the engine to both be happy.

 

[250Gimp]

Re: Update - New prop seems to slip a lot

That makes sense to me on paper...

Even if you're revving a little high with the 25 pitch (up to 5,000-ish), you'll be good for watersports and it won't hurt that engine at all....as long as it's enough to keep it off the rev limiter I would expect you and the engine to both be happy.

My thoughts exactly Craze1 !

Thanks for your input!

Cheers

 

[Tail_Gunner]

Re: New prop seems to slip a lot

Re: New prop seems to slip a lot

Ok, update!

I tried the 23p high five, and I am still over revving!

I am hitting the alarm at 5200 rpm doing almost 52 mph by speedo.

I am thinking of going to a 25p to try, but that will be an expensive experiment.

The old prop I had is 15-1/4" diameter Bravo 1, 24p, and the Highfive is 13-1/4" diameter.

Anyone have any thoughts on this?

I am a bit baffled, as I am only running a 4.3l MPI, and my boat is fairly heavy!

I calculated the prop slip at abround 17% for this set up. Is that good for a V hull?

Thanks

Some thoughts 17% slip is dismal for that boat. A good number is 10..11..While i cannot be certain i do believe you rev limiter is capped at about 4950 and if so you may want to call merc support and see just where it is capped....I do not mean to quarrel with diameter but 13.25 is a outboard prop

http://www.google.com/search?sclien...615&emsg=NCSR&noj=1&ei=0f5DTojsAob4swPSvomsCQ


This can be very simple.. mate the prop to the drive hub....there should be a 3/8 gap between the two...that is the prop barrell is smaller than the drive case creating turblence or a disturbance in the water flow which prevents your prop from hooking up both at launch and at wot...You are getting the exact opposite results that a multi blade was designed for.

You have however may found a way that may allow I/O's to produce the same wake as a boat produced to do just that (wake board boats) without producing unnecessary load on the engine..In short a mismatched hub does not hook and plows ...creating a large wake dragging the stern and at low rpm keeping the boat off plane. If so my sons will be quite plzd with your results....Good thread

 

[250Gimp]

Re: New prop seems to slip a lot

Re: New prop seems to slip a lot

Hey There Gunner!

The High five is made to run on an alpha leg, as well as outboards with the large casing/leg (or what ever they call it). I got the part number directly from Mercury so there was no confusion with the outboard version.

I didn't look specifically at the gap from the barrel to the hub, but there seem to be a difference from my Bravo1 prop, as I remember. I will double check tonight!

I think part of my problem/confusion is that my drive is a lower than normal gear ratio at 1.81 compared to 1.6+/- for the majority.


Cheers

 

[craze1cars]

Re: Update - New prop seems to slip a lot

FWIW....all High Five's are 13 1/4" diameter...or smaller:
http://boatpropellers.iboats.com/Mercury_Marine-HighFive-Propellers/

And are specificially recommended by Mercury Marine for V6 powered Sterndrive boats:
http://www.mercurymarine.com/propellers/elite/high-five/

I continually admit to not knowing much about High Fives...in fact they confuse me a bit. But I believe Mercury knows a thing or two about prop design and matching diameter with intended usage....

High Fives can't be found in a larger diameter than that...period. And I am quite certain that the prop barrel of a High Five is the same diameter as the outdrive case....

 

[emilsr]

Re: Update - New prop seems to slip a lot

FWIW, I had similar problems with the High 5 running it on a similar hull with a 260hp 5.0. It slipped....bad....never really felt hooked up and the performance was not good at any rpm range. Take this with the proverbial grain of salt, but the prop "gurus" I talked to said it was more suited to a high power outboard running a high drive height.

Wound up with a Turbo 2+2 TH and, out of the 6 or 8 props I tried on that boat the Turbo had far and away the best overall performance.