[bbrophy58]

I have a 2000 Mariah Shabah with the 4.3 carbed mercruiser 190hp. I am looking to move from a 19p to a 21p prop for more top end. What brand is recommended? What diameter are others running? I see everywhere from 13 3/4 up to 14 1/2. I do not want a 4 blade. Anyone have a recommendation? I hate to just buy one and hope it works for my needs.

[mikeyt]

I'm sure you already know this but i'll repeat it anyway. Moving up to a 21" prop will cause you to lose your low end acceleration & hole shot. That said: if its a 21" you want then 14.25 x 21 is the standard size. It wont hurt to be a 1/4" larger in diameter. In aluminum i would suggest a Michigan Wheel Vortex or a Quiksilver Black Diamond. Both are good general purpose props. If you are feeling a little flush & want SS then i would suggest a Stiletto Advantage.

[bbrophy58]

Thanks Mikey. I understand I may lose some bite, but I think the type of boating I do may be more suited to the higher pitch prop for speed and efficiency. Typically my wife and I boat together, sometimes with another couple, but many times just the two of us. We are not usually skiing or pulling water toys. Mostly we cruise about 30 miles down a river in Massachusetts into the Mount Hope Bay in Rhode Island and hang out in Newport for lunch or shopping. I do have smart tabs and a well tuned engine. I need a spare prop anyway and was thinking we could swap the 19 and 21 depending on the load for that day. I think you told me a while back that you have both sizes. Is the 21 too high for this set up? I like the higher top end for a quick rip once and a while. I really appreciate your advice. Thanks!

[mikeyt]

Nah, the 21" will work just fine for mid range cruising but just dont expect much in the way of low end grunt or acceleration. I have a 20" 4 blade & a 21" 3 blade and if i'm going for a distance cruise i will throw on the 21".

[Slash9point5]

We have a 1995 Mariah Barchetta 182 with a 4.3L mercruiser and we operate a 21Pp SS prop. For us it seems to have plenty of low end grunt because we do a good deal of wakeboarding and even with 3 guys in the boat and a 195 lbs guy on the wakeboard, our set-up still gets out of the hole just fine.

We also tend to have the max number of passengers on board more often than not because we are the first of our group of friends to have a boat. And I am happy to report that as long as one person sits up front (which one has to anyway), there are no issues with even 6 people in the boat.

I do find it a little odd that we get such great results, but it must be repeatable because it performs well all the time.

So, I imagine the 21p prop would also work well for you, especially since you have smart tabs.
.

[mikeyt]

Originally Posted by Slash9point5

We have a 1995 Mariah Barchetta 182 with a 4.3L mercruiser and we operate a 21Pp SS prop. For us it seems to have plenty of low end grunt because we do a good deal of wakeboarding and even with 3 guys in the boat and a 195 lbs guy on the wakeboard, our set-up still gets out of the hole just fine.

We also tend to have the max number of passengers on board more often than not because we are the first of our group of friends to have a boat. And I am happy to report that as long as one person sits up front (which one has to anyway), there are no issues with even 6 people in the boat.

I do find it a little odd that we get such great results, but it must be repeatable because it performs well all the time.

So, I imagine the 21p prop would also work well for you, especially since you have smart tabs.

Hard to compare directly as you have a different year, a different model and different weight which all add in to the effect on a boats performance. Glad to hear your Barchetta performs well with the 21". There is someone else here (my senility is kicking in & i can't remember who it was) that runs a 23" prop on their 94 Barchetta 180 and is very happy with how it performs. My '96 Shabah 180 didn't do well with the 21" at wakeboarding etc until i installed Smart Tabs and the 20" - 4 blade prop but it did cruise nicely. Bbrophy's 20' boat will weigh more that ours & is using the same motor so it will work just a little harder than ours at getting onto plane. The Smart tabs will definitely help and having a choice of props available is always a good idea.

[bbrophy58]

I really appreciate all of the input you guys have provided. Just to clarify, my boat is a year 2000 Shabah 182, I think the same hull as MikeyT. I may have added some confusion by saying it was a 2000. Not sure if the year makes much difference. I run a 19p aluminum prop with smart tabs and get great hole shot and about 47mph top end and 4900 rpm. I think the smart tabs I added may have slowed me down a couple of ticks, but are great overall and my best upgrade to date. I have tried most of the smart tab settings and use the second lowest for every day cruisiing and the middle setting for the few times we go skiing. It is probably just my male ego, but the 50mph club would be fun and a planing at a lower rpm for my weekly 30 mile run down the river would also be a bonus. This morning I am tucking my boat into a garage for the winter and will wait anxiously for spring. Based on all that you guys have said, I will grab myself a 21p prop over the winter. I will stay with aluminum as a precaution. Already lost my original prop to a pesky rock! Oh, here is a picture of my little guy docked in Newport RI for an afternoon lunch. In the words made famous in the movie "Jaws" ......"I think we need a bigger boat" Might have to look at that 302 for sale. Thanks everyone.

[Will of Shellharbour Aust]

Hi, I have a 2006 SC23 with 230hp carb motor the prop that came with the boat (I'm second owner) was an 20 inch 4 blade aluminium which has been damaged . The boat always cruised well but took a long time to get to plane especially with more than 2 people on board.

As I have no starting point other than the 4 x 20in can some one help me with info as to the best all rounder to go for , SS is ok but the 3 vers's 4 blade and pitch size has me scratching my head.

Thanks
Will

[mikeyt]

Was the prop damaged when you bought the boat? That would likely explain the planing difficulties. With your boat a 19" or 20" would be about the right pitch. To give an accurate assessment though we really need to know what your rpms were at WOT. You can always visit the Mercury Prop Selector site and plug in your information to get an accurate starting point.

Basically, lower pitch results in higher rpms and better holeshot but reduced top speed. Higher pitch reverses each of those results. 4 blade props tend to provide better acceleration & smoother cruising but usually at the cost of a little off the top end. Your engine (5.7?) has an RPM operating range of 4400 - 4800. Ideally, your WOT rpms should be very close to 4800 but as long as you stay within that range your motor is running efficiently.

[Will of Shellharbour Aust]

Gday Mickyt,
Thanks heaps for getting back to me .

My motor is a 5.1 Lt 230 hp.
No the prop was not damaged it was new when we got the boat , we hit a submerged rock up the river on Friday ( we weren't going very quick so only prop bought it) .
The previous owner placed the 20 inch alu prop a week before we purchased the boat he had not even tried it out.
Hence my problem with no starting point cannot find out what prop was on the boat originally .

The WOT is about 4200 rpm with the 20 inch prop and 40 mph, by my reckoning this is down on what it should be ...but not knowing what is factory .

I have gone to the Merc site and have placed all possible WOTS and mph's to 46 mph to see what is recommended again just started to get more confused.

Big problem out here is there are so many so called experts on out boards with none installing me with confidence about inboard/stern drives .
Thanks again.
Will