Alu to SS - Ventilation issue ?? or Design feature ??

[QBhoy]

Don't know about you, but I don't care how much slip I have at WOT. I can count the number of minutes I run WOT in a season on a couple of fingers.

I'm concerned about slip at cruise (4200 - 4500 rpm) where I spend the majority of my time. At those rpm I'm running at 5-6% slip.

What is your cruise RPM?

That’s incredible slip at cruise. I’ve never even thought to gather numbers for cruise Prop slip...but I’m almost certain that my hull wouldn’t be anything close to that. It can’t be I’d think. For me to get down to 3% or on the odd blue moon, just under...my boat needs to be flat out and aired out up on its pad with just the drive in the water. At cruise speed it’s doing late 20’s mph and 2300 rpm approx. With more than half the hull in the water. No way I’d think I’d even be under 10%. I’ll need to experiment

 

[Stinnett21]

Yeah I might have to bite the bullet at some point. It's eating at me. I boat on an inland flood control lake so debris abounds this time of year. Need to wait till at least mid summer/fall. Don't won't to be forced to buy something I don't want.

 

[Canufixit2]

Hi, OP here.

Follow up original Post. I changed to my SS for Three reasons, 1) To add a few RPMs to WOT and 2.) fix prop rattle at Min speed and 3) I Bought the Prop , barely used, on Ebay for $110 !!

This SS Prop, as stated above, has Some slip on Stopped to WOT take off. And Does hold great in tight turns. Also, As Mercury has said this slip is not an issue for the Motor, So ... I'm Happy. However, IF I were to change the prop to another $tainless Steel, I'd attempt do the following.
Buy one with, Solid hub (no rattle),
One pitch higher (14x 11 if possible)
and aftermarket SS (To save some $$'s).

JMO Thanks all for the help !!! SteveC

 

[dingbat]

That’s incredible slip at cruise. I’ve never even thought to gather numbers for cruise

Of prime importance of those of use you point the bow East and arrive at our destination 2.5 hours later.

Running a Ray Hunt designed “deep V” hull.
https://m.youtube.com/watch?v=-nm2iAKvKNA

 

[QBhoy]

Of prime importance of those of use you point the bow East and arrive at our destination 2.5 hours later.

Running a Ray Hunt designed “deep V” hull.
https://m.youtube.com/watch?v=-nm2iAKvKNA

Also important to me...but as far as I know...there will always always be a higher slip number, the slower you go and more hull there is in water. It’s just physics, I suppose.

 

[Canufixit2]

OK ... Follow up. Ordered and installed a "Solid" pressed in hub - SOLAS New Saturn 3 Blade Stainless 14" Dia. X 11" Pitch SR. My results/opinion.... Shifting to F /R had a nasty clanking (since the Hub was now solid!). Min forward speed (900 - 1200 RPM) was worse. ALL Vibration in the engine (4 stroke harmonic vibs low RPM) was now transferred to the Engine and into the Solid Aluminum Pontoon. All from the Solid Hub. Now, Otherwise - the prop was great. Little slippage on full throttle take off, RPMs at full throttle about 5800. Ran well, held corners well.

BUT as a pontoon that I use for trolling and min speed cruising - it was just terrible. Perhaps a Wooden/fiberglass boat would absorb the harmonics - but NOT on on my ALU pontoon. I returned the prop and went back to my original Alu prop and all is well - just slight prop chatter at min forward speed.

As for the Chatter, I've done a lot of measuring and thinking on the Hub III mount kit. I'm making a brass spacer to try in the hub to remove Not ALL of the slop in the Hub kit design. I'm making a .125" Thick x 1.75 OD x 1.5 ID" Spacer that will be placed in the Splined insert at the Rear of the splined hub. This will still allow abut 1/6" Slop and will only be in contact with the prop/splined insert when in reverse. Note - for other speeds beside min - hub design for the III kit seemed otherwise OK ... I'dd advise when I try this out .... "IF" I make one than one shim - would anyone be interested in a shim ?? Thanks all for reading/healing/replying ...

 

[dingbat]

As for the Chatter, I've done a lot of measuring and thinking on the Hub III mount kit. I'm making a brass spacer to try in the hub to remove Not ALL of the slop in the Hub kit design. I'm making a .125" Thick x 1.75 OD x 1.5 ID" Spacer that will be placed in the Splined insert at the Rear of the splined hub. This will still allow abut 1/6" Slop and will only be in contact with the prop/splined insert when in reverse. Note - for other speeds beside min - hub design for the III kit seemed otherwise

I too had a lot of chatter on the troll. Drove me nuts on a glass hull. Can't image the ringing in aluminum.

Anyhow, I ditched the Merc Flo-torque hub for a Rubex rubber hub kit. Made all the world of difference.

Little to no chatter. Significantly reduced the amount of slamming going in and out of gear.

 

[Canufixit2]

Thanks Dingbat. IS the Prop you using Mercury ?? I'll keep your suggestion in mind should I decide to change my prop in the future!

Boating only hurts when your not ....

 

[dingbat]

Thanks Dingbat. IS the Prop you using Mercury ??

A Merc Enertia to be exact....

Love the prop, hated the hub. Problem solved

 

[Canufixit2]

I too had a lot of chatter on the troll. Drove me nuts on a glass hull. Can't image the ringing in aluminum.

Anyhow, I ditched the Merc Flo-torque hub for a Rubex rubber hub kit. Made all the world of difference.

Little to no chatter. Significantly reduced the amount of slamming going in and out of gear.

Hi, One more question .... what was the pitch of this Merc Enertia as pitch makes a difference with low speed chatter ....

 

[dingbat]

Hi, One more question .... what was the pitch of this Merc Enertia as pitch makes a difference with low speed chatter ....

The Enertia is 15 x 15.

The Evinrude Offshore 14.25 x 17, 4 blade (solid hub) doesn’t chatter at all. It wasn’t until I went to the two piece hub that the chatter started.

Replace hard plastic with rubber problem solved