What prop are you running?
 

I have a 18 ft Barchetta with a 4.3L. It has a 21P quick silver prop. It planes in 4-5 seconds. At WOT it turns 4900 rpms. I want to bring the rpms down a bit. I am considering going to a four blade prop. I am a family boat man and pull a tube or wakeboard more than running WOT, so top end is not that important. Any suggestions?

I'm running a 14.25 x 21p aluminum 3 blade on mine. My understanding is that if you go to the same size in a 4 blade you will lose about 200 rpm & 1-2mph off your top end but gain extra bite and holding thru the turns. I'm interested in what you find out though cuz i'm considering a 4 blade ss 21p prop also for the same reasons.

Sizing the prop for your boat is technically somewhat of a "guess and check" procedure as a number of factors come into play when sizing a prop. Always keep in mind that you need to size your prop taking into consideration your normal operating weight while keeping into account the specified WOT rpm range for your engine. A good technician should be able to help size a prop for your boat or at least point you in the right direction.

Basically, the higher the pitch of the prop, the lower your WOT rpms will be.

Sizing:
Install prop, load boat accordingly, get to WOT - check RPMS, then:

If your engine speed exceeds your operating range OR you hear you engine hitting the rev limiter (fluttering noise) reduce speed immediately... go get a higher pitch prop.. Excessive engine speeds are bad...

If your engine speed is outside and below of the specified range get a prop with less pitch. An under-revving engine aka "lugging" is also bad... It puts excessive loads on engine internals and your outdrive.

Thanks for the reply. I was just wondering what other people had and how they performed. At WOT with the boat loaded with family and coolers it still hits 4900 rpm. I was thinking of going to a 4 blade same pitch or add 1" diameter. I really don't want to go to a 23p for fear of poor hole shot.

I believe the hub size on my prop is a 14 1/2 and I know the pitch is 19 and it is a 3 blade. It is just the stock Merc Blackmax. Nothing special, nothing hi-perfmance, just all-round use is good with me.

I have ordered a replacement prop for mine, since I noticed one of the blades was bend and had a small gouge in it as well.

I am running a custom Ron Hill Signature 5 blade, 19P. WOT is roughly 4800 RPM with a posted speed of right about 50MPH. Although, I've never check or verfied with GPS. My outdrive is an Alpha with a 1.63 gear set, that is coupled to a Merc 350.

My hole shot is amazing, I can't seem to get it to blow out and handles phenominal. The most important thing to me was it removed the porpousing that drove me nuts anytime my boat has trimmed at all. If I keep the boat, I am also going to add trim tabs and convert the measly 2bbl to a 4bbl. That should help my appetite for getting it up on plane quickly. I have picked up a vibration back there though, so I wonder if I need to bring it in to get balanced at a prop shop. I had my drive removed and checked and fortunatley that is a-okay.

What is Original Prop Spec for 3.0 L
 

I have a 1994, 18' Talari with a 3.0L. What is the original prop spec for this setup? Thanks.

Likely a 14.25 x 19"p 3 blade aluminum will be the original prop for your boat. Yours should be identical to 180Diablo's.

I'm running a 14.25 x 19" Stiletto on my '95 Talari 180 with the 4.3 2bbl. Top rpm is 4950 and 49 mph was the best I ever ran per the speedo.

Since I've added the Smart Tabs (best money I ever spent), I had toyed with the idea of going to a 21 inch pitch, but didn't want to buy another prop.

Oh come on, Paul - you own a BOAT, don't you?!?!? Break Out Another Thousand. Help the economy! :yes_grin: