Props

Nubs45 · 08-13-2013, 05:48 PM

I just wanted to share my experience with props in case anyone else is exploring this issue.
I have a 96 Shabah 180 w/ 4.3 Alpha One. It came w/ a 3 blade 19p SS prop. Seemed to do pretty well but would hit the rev limiter at about 4800rpm and 48mph. ( At first i didnt know it was the rev limiter) I came across a guy with the same exact boat. He had a 4 blade 21P aluminum. We lined up on the lake. He had a quicker hole shot and said he could pull bout anything he wanted. After researching locally, no two shops agreed. I was refered to propmd.com. They gave me alot of info, I tod them I wanted to pull a 300lb skiier. I bought a 4 blade 19p SS. Wow what a difference. It has got some power now. even with 4 adults, It will still do 45MPH at 4600rpm, no longer hitting the rev limiter.

***mikeyt*** · 08-13-2013, 10:05 PM

Interesting but....there is no way a 21" prop will out-accelerate a 19" prop on two IDENTICAL boats from a standing start. Take a few minutes to read the stickys at the top of the Prop Talk Forum.

As for your situation trying to pull a 300 lb skiier.... you would have done slightly better with a 4 bade 18" pitch SS prop although i wouldn't recommend that prop for general usage. It would have moved your WOT rpms up to 4800 which is the maximum (& most efficient) recommended range for your 4.3. You mentioned your rev limiter kicks in at 4800 rpm? Either your tach isn't reading correctly or someone has been playing with the limiter. It shouldn't kick in until you reach around 5100 rpm on that boat.

Nubs45 · 08-13-2013, 10:40 PM

It did. At the time we 'drag raced' I had a 3 blade 19 to his 4 blade 21. We lined em up 3 times, each time he was on plane at least 2 boat lengths ahead of me, of course i caught him, but he was up quicker. Im really happy with this 4blade 19, big difference. You are right on the rev limiter.the needle was near 5k when running the 5 blade. it was just hard to focus with all the bouncing at that speed it was hard to tell. i would back off and it ran fine. Now that i have the 4 blade, I dont hit the limiter, I only pushed it that one time when the water was smooth otherwise i would have looked like a dolphin jumping out of the water (bad porpoising issue) and still tops out at 45mph, I would rarely go that fast anyway.

***mikeyt*** · 08-14-2013, 12:05 AM

5 blade? you didn't mention a 5 blade prop. I will repeat myself for your benefit: there is no way a 21" prop will out-accelerate a 19" prop on two IDENTICAL boats from a standing start. When you are referring to your boat with the big missing pieces from the skeg and the cavitation plate, that makes a considerable difference as your boat wont plane properly. Or were you pulling that 300 lb skiier when you had your 'drag race'?

Nubs45 · 08-14-2013, 12:11 AM

I meant to say 4 blade not 5. I don't know what to tell you bout lining up with the other boat. I was there.

It wasn't a fluke. Did it 3 times. I caught him and passed him but he was on plane sooner. It's just fact. Remember I had a 3 blade to his 4.

***mikeyt*** · 08-14-2013, 03:02 AM

I'm quite familiar with prop performance... I think you missed the point of what i was saying. My BOLD print saidIDENTICAL boats. Yours has some significant defects in the outdrive which seriously affects your planing ability which means that your boat couldn't get out of the hole like it should. I'll also suggest that the IDENTICAL boat with the 21" 4 blade will have a higher top speed than yours will with a 3 blade 19" prop. And i suspect that your boats were not IDENTICAL (ie Mariah 180's) or i'm sure we would have heard about the drag races on our site from the winner rather than the loser.

Nubs45 · 08-14-2013, 03:47 AM

Doing that side by side comparison is what led me to the 4 blade 19 that I have. He was good enough to take the time for us to drive each others boat and
do some comparing. He had never seen anyone with the same boat.
Yes they were identical. We inspected each others boat for quite sometime. Only difference was the shade of green on the interior.. With the set up I have now, I can get on on plane
in about 3 boat lengths depending on the load.
I'm sure you guys are right after seeing the pics of that chunk out of the lower unit. I
didn't know that would effect planing. Thought that rib was there for stength more than anything.
I will address that next season. I know that will be expensive so I may try the smat tabs and see how that does
since that will be much cheaper.
I never knew this site existed until today when I stumbled onto it.

***ColoradoDiablo*** · 08-14-2013, 04:16 AM

You gotta fix it one way or the other!
That "rib" that is around the drive is made to help you plane , and have control over the boat.
Tabs will make it less noticeable , but why run a boat that isn't running the way it was meant too?

Spend the money to fix it. You'll love it in the long run.

Nubs45 · 08-14-2013, 11:40 AM

Your right, Larry. I've always been a stickler about doing things right
and thorough. I will do some searching during the off season and see what I can find.
I gave mis info earlier. That other boat in my side by side tests had a 20p aluminum
not a 21. Hope that makes better sense. We shut down just seconds after planing.
My apologies on the flub up.

Andy b · 08-14-2013, 11:47 AM

This "rib" that you are referring too is the cavitation plate. it's job is to keep the water around the prop and stop Cavitation, as the name suggests.
With the damage being at the front of the plate your prop will be grabbing air and causing the blades of the prop to lose grip. This is why your hole shot is not as good as the other boat.

Many other factors come into a great hole shot like having the boat set at the correct trim though out the procedure.

are you sure that the other guy wasn't just a better driver than you.....