Props?
 

I am guessing this topic has been discussed several times in the past but I haven't been a member that long and would like to ask it again. Looking for suggestions on props for all round use. Not interested in going real fast. Mainly just cruise and wakeboard. I would like a prop that really holds a constant speed even when towing a heavy boarder.

Assuming you have mercury power, one way to get a good idea is to see what merc recommends. You can use their prop selector tool:

http://appcenter.mercurymarine.com/propSelector/home.do

You will have to know the specifics about your engine type, drive ratio, WOT rpm, and current top speed. It should give you a good idea of where to start. You can adjust the selector tool to fit various preferences in term of what you are looking to get (top speed, watersports, acceleration, etc.)

As Z202 says...the Mercury prop selector tool is a good place to start. The thing you have to remember though is that you dont want your engine running outside the recommended RPM range at WOT. What engine do you have? What prop do you have on the boat now and what RPM's do you read at WOT?

With your 182 and i'm assuming you have a 4.3L engine, a 3 blade - 14.25" x 19 pitch prop will be a good start and a 20 pitch - 4 blade will give you a little extra bite. Also, as one of our other members noted, altitude affects engine & prop performance. SS props perform better than aluminum props but at a higher cost and cuz they are much harder there is more chance of damaging a drive shaft if you strike something solid. But.....a lot of this is trial & error along with some educated guessing so lets answer the initial questions & go from there.

MikeyT is correct, propping is not an exact science as I have learned. I recommend buying a prop from a local shop that will work with you to find the right one. They should let you test different props to find the one that gets you the performance you are looking for.

Hey Mikeyt, I see on several posts that you seem to be quite knowledgable on props so to answer your questions I have a 4.3LX with 14.25x19 as well as 21. The 19 works ok but is slightly damaged and I don't want to run it and risk damage. The 21 is probably the right prop for the boat as I can go about 50mph with 3-4 people at just under 5000RPM. The problem is that the boat is a dog with this prop and it is very hard to plane towing a skier/wakeboarder. I am not concerned with the over-reving problem as I am the only driver and will make sure to watch RPM...or I'll be buying an engine. I would be more than happy with 40-45mph if I could get a good wholeshot for wakeboarding and mid range power to hold while the boarder cuts back and forth hard. I think I would like to go to a 4blade based on reading on this and other forums but should I get an aluminum or SS and 19 or 20. My local dealers suck and won't work with me at all as far as trying props out so I need to do it right the first time. I realize there has to be some compromise, and in my case I am willing to sacrafice top end for bottom end and mid range performance. The next thing is that I need to source a prop ASAP from a local dealer that has stock so if you have a couple suggestions(brands) it would be appreciated.

Hi Kurtis

If you are already over the max RPM (4800) for your engine with a 21" pitch prop, dropping the pitch to a 19 will increase your RPM's by about 400 which will take you way over the limit. I would consider a 4 blade, 20" pitch SS prop to keep you RPM's within reason. There are a number of good brands out there but i would consider a Mich Wheel Apollo prop which seems to be good value for the money. The Stilletto Bay Pro is another good 4 blade prop.

Just out of curiousity...have you checked to make sure your tach is at the correct setting for a 6 cyl motor? Hitting 5000 rpm with a 21" pitch prop seems a little high.

I've checked the tach and it is in the correct setting. I've also turned it back and forth as per one of the posts in this forum just encase it was making poor connection etc. My 19" prop was a second prop that came with the boat and has a slight gouge in one of the blades....maybe I'm getting a lot of slip as well??? Don't know the history of the prop...definately not new. Looks quite old.

I am now being told that a 4 blade aluminum Mercruiser prop in an 18" pitch would be about the same as the 19" 3 blade for max RPM. That is what one local shop told me. Most shops around my parts recommend aluminum because of the small shallow lakes. This is a much cheaper option than SS in the event that I am not totally satisfied with it?

maybe i didn't understand earlier. Are you running the 19" pitch prop or the 21" pitch prop and getting 50mph @ just under 5000 rpm?

If its the 19 then yes an 18" 4 blade will be very close just as a 20" 4 blade will be very close to a 21" 3 blade. What you will get with the 4 blade is a little more 'bite' & low-mid range acceleration. You might lose 1-2mph off the top end.

There's no question an aluminum prop is a cheaper option if you are usually running in shallow or rocky lakes and there will only be a very slight performance loss so if that works for you then go for it. ;)

Sorry for the confusion. I was running the 21 to get 50mph at 5000RPM. So I realize I am going to over-rev with anything lower than that but I have not choice. I need the power. I haven't tried it yet but I am going to purchase an 18" 4blade aluminum which should be close to the 19 3 blade as you stated. I will just have to be carefull with RPM. I appreciate your insight....now if I could find a carburetor expert to chat with me in the Boating101 forum I would be in business?

Thanks

I have the same setup. A 4.3L with a 3 blade 21p ss prop. I would suggest that if you want to get out of the hole, get smart tabs. I just put a set of composite ones on my Barchetta and it gets on plane much quicker. It seems to hold a constant speed better as well. I have also considered going to a 4 blade prop but since I put the tabs on, I like it the way it is. If you decide to get the tabs, get the 60lb. actuators.

I went with a 4 blade Alpha 4 aluminum Merc prop. Works well out of the hold and planes way faster...even with 2 people sitting in the back and none up front. As expected, the downfall is top end which is about 42mph with 4 adult and 2 kids at about 4800-4900 RPM. Overall I am very happy with my choice and I continue to shy away from Smart Tabs as I haven't found anyone yet that is running them and using their boat primarily for wakeboarding. I am told that they flatten out the wake considerable which is good for skiing or tubing but not for wakeboarding.

I use two props. My main cruising prop is a 21P Vengeance (3blade SS). When I want a better hole shot, I put on a 20P 4-blade aluminum prop (Solas or something else "cheap"). I also usually put on the aluminum when going to new lake, especially inland lakes. The 20P 4-blade increases the bite, holeshot, and the RPMs by about 200 (it's my poor man's High Five). It will also be much cheaper to replace after hitting a rock. An 18 might be a little skinny for you boat based on what you have written.

I keep both props on board just in case I need to change one out. I have changed it in deep water without tying anything off, got lucky that nothing sank to the bottom, and saved my outing!

Regards,

You may be right about the flattened wake with the Smart Tabs Kurtis. I took my 14 yr old out wakeboarding on the weekend and noticed that the wake was fairly flat...

In all the posts I've read I have yet to see many people worried about having a big wake...most don't mind a smaller wake. But I think it should be known to those who are considering Tabs that it may affect their watersports experience?

Having said that then, what is the alternative if one is looking for Smart Tab like performance with a big wake? Are we back to Hydrofoils?

Hydrofoils.....uggh. Not sure what other alternatives are out there. It sounds like you cant have your cake and eat it too.... :shakehead:

If you can stay on plane at boarding speed you shouldn't have much concern for tabs. Most reviews I've read have always raved about how decent a Mariah's wake is for boarding. I'm not sure I'd jump to the Smart Tabs and spoil a good thing...

Properly loaded and trimmed, I can get down into the mid 20's with my 21p Vengance and stay on plane without Tabs. l'd like to follow Captain Steve a pick up a 4 blade aluminum for watersports, but the SS prop ate up my prop budget for the season...

Hello Guys,

I have recenlty fitted smart tabs to my 3 litre Mariah 182 bow rider, it is running perfectly well however the prop needs to be changed as l damaged it last time out, l grounded it and took a larg chunk out of it. It is the original aluminium prop, what is the best prop for me to go for? at present l can get 40mph out of her, would a stainless (or different alluminium) prop increase my top end speed if so what is the best to go for?

Cheers,

Gary

Hi Gary,

Do you happen to remember what RPM's you were at during WOT? 40 MPH seems about right for your set-up. Anything that would increase top end will slow you down out of the hole. The Smart Tabs definitely help planing, but you'll still be pushing a lot of water for extended time if you go with a higher pitch prop.

One thing you might want to try is a 4 blade prop one pitch higher than you had. That's usually a good compromise to sustain both ends of the performance spectrum.

A stainless will usually help all around, but I wouldn't suggest it if you have a lot of "opportunities" to hit something submerged. They aren't nearly as forgiving and could cause more damage to the lower unit.

Excellent advice Ryan, Thanks.

The boat yard l store her in said the same thing about the stainless prop and damaging the bottom end if l ground her, l am always using her on Loch Lomond (Scotland) and beaching her to allow the kids and wife to enjoy the lazy days on the islands so l will most certainly be sticking with an aluminium prop, l will see if l can get a four blade the next size up, is the size of the prop written inside the shaft area once it is removed?

Regarding the RPM, this is is the only thing that it is not working on my boat, l wil be repairing the rev counter next time home in August.

Cheers,

Gary.

The prop spec's are usually stamped on the hub, around where the prop nut is. It will either specify the dimensions (i.e. 14x19p) or it will list a part number (48-######A##) which you search for on the Merc site to obtain the specifics.

Hi Guys,

Thanks again for the info, the boatyard checked the prop this morning and said it is a 19 pitch, they measured from the centre of the shaft to the outside edge of the blade and it was 13 1/2" the number on the prop was 48 832 830 A45, is this the standard prop for a Mariah 182 3 litre? should l move up to a 14" 19P for a little more top end speed will the engine and leg be ok with this?

Cheers,

Gary

Hi Gary

It's the increase in pitch (not diameter) that will provide a higher top end. Note though, that it may make your boat a little sluggish out of the hole. Increasing the pitch will also lower your rpm's at WOT. You may find that the 19" pitch gives you your best compromise.

I used to have a 1996 Crownline 175 Bowrider with a 3L 4-cylinder and Alpha drive. It came with a 19P 3-blade aluminum prop and after break in, I noticed it ran at or or just slightly above the maximum RPMs of the allowable range. I bought a 21P aluminum 3-blade prop and she ran a little faster at WOT with a few less RPMs. Either prop was basically OK, the 19 was good for heavy loads and water sports, and the 21P was just fine for cruising with my First Mate and small child. I expect that you could use either on your Mariah.

The 3-blade Mercruiser props seem to come in odd pitches only. I started looking at 4-blade props and found they run in even pitches. Everybody now knows that I run a 20P 4-blade aluminum prop on my Z210 with a 5.7LX and Alpha drive. It is kind of like my poor man's High Five for water sports and hole shots. For cruising on rock-free lakes (like southern Lake Michigan) I mount up the 3- blade stainless steel 21P Vengeance for maximum cruising efficiency and top end.

Best regards,

Hey Border1010...I have an aluminum 4-blade 18P prop with Smart Tabs and you are right about the wake not being very big. But the performance between the 4-blade keeping a constant lower speed and the Tabs planing my boat out quickly....I can't complain.

When I want a bigger wake......I usually shorten my wakeboard rope appx 15', and wow what a difference. My rope has three sections, which I will go down one section (which is probably 15-25'). Makes a difference. As far a hydrofoil......I used one and it helped out as well, but the tabs give me a smoother ride across the lake in general.

So everything I have read here, I must have a problem... New to boating so be easy with me.. I have a 4.3 with a alpha 1, 3 blade 19 pitch and a rpm of 5300... I sounds like my rpm is way to high???? boat will run about 50 mph and pull 2 skiers... but if I pull a wake or knee boards of the heaver side its hard to keep a constint rpm... help!!!!

I think that is a good problem to have! The lakes around you are probably at about 400ft above sea level which helps the engine run stronger(better air), you could probably stand to go to a 21p prop and will pick up another 5 or so MPH and drop your rpm to about 4800. You will lose some bite out of the hole, if that is real important to you check into a 4 blade prop. I would go to a local prop shop that will let you test different props until you find the one that you like the best. That is assuming your Tach is set to a 6 cylinder engine, may want to check that on the back of the tach.

I will check the tach tonight.. I didnt think anything about the rpm I thought it was in range cars are about 5500 with that engine so I thought I was ok... I dont want to hurt the little thing you know!!! I think I can try props in Havasue thanks for the info...

I have a 4.3 alpha 1 20 foot shabah. I am running a ss 3 blade turbo prop. Not really sure of the pitch, I will have to look tonight. I run wot at about 5400 rpm and about 58 mph. I have a hydofoil on the lower unit, no smart tabs. My hole shot is great and I plane out very quick. Not really looking for more on the top end but I sure don't want to damage the engine with the high rpm. Any comments for me? I can always stay out of throttle to keep my rpms down but that is kind of hard to do.