I wanna prop
 

I need a new prop for my 18ft 1999 Mariah Shabah 190 hp merc cruiser where can I get the best deal ? and what is the best diameter and pitch for just pleasure boating and a little skiing and tubing ?

Thanks,
Jim

Re: I wanna prop
 

Probably a 19" 3 blade or a 20" 4 blade. Search for a Mercury Spitfire aluminum unless you really want to spend the $$$ on a SS prop.

Re: I wanna prop
 

Thanks for the information, I appreciate it.

Jim

Re: I wanna prop
 

I've got a good 19" 3 blade with a bad diffuser ring and a messed up one with a good diffuser ring.
I'd sell em cheap but I don't know if it'd be worth the savings after shipping. PM me if you're interested.

Re: I wanna prop
 

How much more aggressive would the 20" 4 blade be compared to a 21* 3 blade at take off?

Im in the same scenario as the Jim Grogan with the same boat basically which came with 21* 3 blade.

Re: I wanna prop
 

As noted in the educational STICKYS at the top of the Prop Talk forum, there is a considerable difference between the two.

Re: I wanna prop
 

:wink_thumbup:Oh i read them trust me.. thanks for the great info. I just didn't know how many pitch * drops is usually a good rule of thumb...i was thinking for our 18ft boats a 19* 4 blade was a very good choise.

Re: I wanna prop
 

The 19P - 20P 4 blade is a good choice , as mikeyt has stated in other threads with like boat / power packages.
But remember , no 2 boats will react the same. It doesn't matter if they are exactly the same in every detail.
Just a fact of nature.:)
None of the 18' 4.3L Mariahs' "came with" a 21P prop(that I have heard of). Someone has changed it in the past:yes_grin:
A 19P three blade was usually the std , with 17P 3 blades on some of the other "higher elevation" boats.
Throw a set of Smart Tabs on her , and she'll come out of the hole like a rocket!:yes_grin:

As usual just my opinion

Re: I wanna prop
 

Of course! Previous owner did tell me he did swap to an SS 21p...not sure why but id like to gain that lower end back up...right now deciding between an 18P or 19P 4 blade. Keeping in mind that a stock came with a 19P makes me think i should go lower as well!

Sorry for stealing thread, hope all this information helps!

Re: I wanna prop
 

The most important thing is to get your engine running in its recommended rpm range at WOT. Once you accomplish that, the engine runs at its peak proficiency throughout the rpm range. Choosing a correct prop allows you to get things working within that range. Note though that it is not cast in stone that you have to limit at 4800. Mine will run at 4950 if it let and it wont hurt unless i'm running there for extended periods of time. Generally for our 18-20' boats at lower elevations 3 props work best; a 19" 3 blade, a 19" 4 blade or a 20" 4 blade. There are exceptions though. Higher elevations usually require a lower pitch blade to make up for the lower power level produced by the engine at those elevations. And... we do have some members who run 21" props and even a couple who ran 23" props and other run 17" and 18"said they worked just fine for what they want their boat to do. Note that these are just general rules of thumb.

Edit: couple the right prop with a pair of Smart Tabs and your boat will literally jump out of the hole!

Re: I wanna prop
 

Very valuable information and all makes sense! Michigan elevation isnt high so i was thinking of looking at the 19* 4blader...that is after i check some RPM runs...

i think right now she did about 52mph (on the dreamometer on the dash) w 4 people in it...not sure of the RPMs tho...

Re: I wanna prop
 

I run a 17" 4 blade stainless, but all I do is cruise and pull tubes and wake boards. I could care less about top speed. I never use it. I bought the prop to get me and people I'm pulling out of the hole without effort.

Re: I wanna prop
 

where do you usually leave your trim as you are taking off and towing people

Re: I wanna prop
 

All the way down to start, and just a couple clicks up when towing. I have smart tabs too, which almost makes it jump up on plane too. I usually tow the wakeboarders 15-18 and tubers a little faster depending on the ride they want.;)

Re: I wanna prop
 

I went through much the same thing in the last month. I had a 19p 3 bladed prop that was putting me way over my RPMs and so I switched to a 4 bladed hustler prop at 21p. Turns out that I could only get to 4200RPM with that prop, but my speed went from 41MPH to 45 MPH. This made me think that the original prop and hub were wonky, so I went back to a 19p 4 bladed Hustler and now the RPM runs at the top of the range.

My boat is an older Mariah 1850 XL with a 4.3L and I use it mainly for watersports. The biggest difference I noticed was that the boat could hold its plane much better at lower speeds and far less RPM. On take off, it reduced the time it took to plane by about 2 seconds, but it felt far more responsive at the same time. I should also mention that, while I know they are frowned upon here, I did install a hydrofoil as well (SE Sport as it was no drill install and I had a small credit at BP so though why not) and that combined with the 4 blade prop have brought my plane speed down from 25MPH to below 20 even when pulling a wakeboarder and my time to plane has gone from 7 seconds with empty tank to 3.5 with full tank.

Those things worked for me and I am happy with it. I know its not what everyone would like, but hey, thats why there are options.;)

Re: I wanna prop
 

Sorry, meant to add that my top speed now is about 42MPH. I think that a 4 bladed 20p would probably be suited more for top speed, but your not buying a 4 bladed prop for speed in most cases anyhow.

Re: I wanna prop
 

So its been about a year and iv added trim tabs to the 18ft boat and have gotten the RPM gauge to read correctly by moving the selector switch in the back a bunch of times...

Top speed went down bit w the 60# smart tabs, but she does take off way better and nose stays way down....my RPMs at WOT are about almost hitting the 5k mark with the SS 21 pitch prop...

My take off feels like it could use a bit more bite...feels like there is a dead spot in the mid throttle and she needs a little love to get up and going...she sits there for a bit and i have to floor it go get her going up on plane faster...(maybe its just the V6 LOL)

This is the prop she has in there right now

http://i22.photobucket.com/albums/b3...psmbqszcbz.jpg

http://i22.photobucket.com/albums/b3...psbf2rlb4s.jpg


With these RPMs at WOT, what you guys think i should consider for a prop situated for a better take off without danger'ing WOT RPMs?

Thanks again

Re: I wanna prop
 

Its unusual that a 21" pitch 3 blade will get your 4.3 up to 5000 rpms but i guess its not unheard of. If you want a little more mid-range without sacrificing too much off the top go to a 4 blade. If you are actually at 5000 rpms at WOT then i wouldn't go any lower in pitch than a 21"

Personally I like the 4 blade Apollo prop i have on my 180. It gives plenty of low and mid-range punch and i think i lost all of about 2 mph off my top end....but then who drives around at full speed all the time anyway?

Re: I wanna prop
 

Mikey i agree with you too on my RPMs at WOT w the 21p...ill try it again (as you mentioned how often do you go wot and stay there) to confirm...then take it from there...i always thought my max rpm should be around 4600 so i always back off when im up there, i just pushed it a few times to get a reading...i been looking at the 4 blades, just not sure what pitch to get...the merc site prop guide even mentioned a 5 blade...thats a little too much and too pricey...

Re: I wanna prop
 

I think that, as you suggested, when the prop was redone they likely altered the pitch slightly and lost some of the cupping on the blades. You have the same motor/outdrive (4.3 - 4bbl, Alpha One) that i have in my Shabah 180 and i use a 20" - 4 blade SS Apollo prop which gets my WOT rpms to 4900. As i mentioned, i really like that prop because of the extra mid-range punch it gives and i could care less if my top speed is 50 mph or 48 mph. That prop combined with the Smart Tabs make the boat literally jump when i hit it above 2000 rpms.

Re: I wanna prop
 

I might have to give this a try....either that or a standard aluminum which is a little cheaper...but i do love the SS...not sure if there is any other places for a better deal...i love iboats customer service...

Re: I wanna prop
 

That's the prop I have and where i bought mine from.

Re: I wanna prop
 

I just bought a 1999 Mariah Shabah 190 hp merc cruiser with a 15 x 17 aluminum and was tripping the limit of 5000 rpm. I borrowed a 14 1/4 by 18 stainless. now I'm at 4900 with trim down and can still limit out by adding trim. This did change the ride to be a lot smother all around. Don't know if it was from going to stainless or not. A 19 might be what I need but I'm looking for 21 to see if I can trim and still get my 4800 WOT. My hole shot is pretty quick and top end is around 47 no trim. I don't really need the extra speed( yea right) but don't want to loose too much shot for big guys skiing. My smart tabs just came so I know I have one plus. If I'm not going in the right direction, I'm sure one of you guys will be glad to straighten me out. I can take it. Jesus is my friend

Re: I wanna prop
 

Personally i have no interest in whether 'Jesus is your friend' and perhaps you could ask him for guidance in choosing a prop but i will suggest that you read thru the STICKYS located at the top of the PROP forum. You should find the answers you seek there for your particular boat.

Re: I wanna prop
 

Mikey...so i ended up getting the 4 blade 20P as recommended...wow...boat jumps up so fast...i'm sure the combination of both the smart tabs and the prop help it get out the water super nice!!! THanks for recommendation!

-LM