Merc Outboard prop change

[mike6868]

Have a 20' Bahner with a Mercury outboard V200...
It currently has a Mercury Vengeance PN 48 16318A45 21P
I'm unsure how to read this part number... I'm pretty sure its a 21 pitch but how do I figure the dia?
Any recommendation for a prop for this boat? I'm thinking of going down a pitch....

 

[WesNewell]

Any search engine.
https://www.mercruiserparts.com/16318a45-ven-13-75x21-rh

 

[harringtondav]

I just did a web search. It comes back as 13 3/4 to 14 1/4" x 21P. A quick way to measure yours is to measure the distance from the center of the prop shaft to the underside of the anti cavitation plate. Then measure the distance from the top blade to the anti cav. plate. The difference X 2 is your prop diameter.

 

[ThomW]

You are correct that it is a 21 pitch. The diameter on that should be 13.75.

change in prop pitch would be dependent on what you want out of the motor/boat.

Dropping the pitch would increase the RPM's, raising the pitch would lower the RPM's. Generally about 200 RPM's for each inch you change the pitch.

What are you hoping to get with a prop change?

 

[QBhoy]

Hi
all I would say firstly is that the vengeance prop is a bit of a gimmick in my opinion. It’s just a shiny version of a standard Ally prop. No real performance orientation at all. In fact, many report better performance with the standard black max ally prop of same pitch.
As mentioned you really need to tell us what you want from the boat. I can’t tell you how complex prop selection can be. So many variables it’s crazy. I’m on my 5th prop in only 3 years. I can tell you that there usually is no one prop does all solution. Won’t go into it in great detail (unless you want me to) but you need to think about whether you want all round use, water sports/variable weight load on boat or top end and cruising orientation. Then you will need to know;

rpm range for your engine
current prop pitch
current rpm with that prop and trimmed well in usual conditions
gear ratio
gps speed with current prop trimmed well and usual conditions

given all the above answered, some guys in particular on here can advise well or at least you can go onto the Mercury prop selector and have an idea. To be fair, it’s usually pretty accurate.
Love to hear more and be happy to help further. God knows I’ve put the time in on my own boats.

 

[QBhoy]

Also. If you don’t mind me asking. Why do you want to go down in pitch ?
Just had a look at your boat type there. Every inch of sense in me is telling me that you should easily be able to run a 21” and more with that set up.
I had a similar hulled boat with a 150 and 200 merc on the back at different times. Both could turn a 23” and at some pace too. Your boat also deserves a better prop than a vengeance too. When you come up with more details...treat her to a laser 2 at least. Better still an enertia !

 

[porscheguy]

Don’t get hung up on diameter. You go by pitch. You’re not going to find a prop of a given pitch offered in different diameters for the most part.

 

[harringtondav]

So many variables it’s crazy. I’m on my 5th prop in only 3 years. I can tell you that there usually is no one prop does all solution..

Absolutely true. My 21P hurls my boat on top of the water in < 3 sec. Great for towing tubes, wakeboards etc. But I have to use my right hand rev limiter. WOT is 52-5300 rpm. My 23P will hold WOT at 4800 rpm. Great for cruising, but a little hard on the engine for repeat hole shots and low speed planing.

 

[mike6868]

all good info! thanks to everyone. I'll stick with my 21P I always thought a 21P was too much for my engine/hull combo.
I can reach WOT RPM of about 5200 5400 at around 55 60 MPH... My numbers could a few off...

 

[QBhoy]

Doesn’t sound too bad with the numbers there. These kind of boats can wildly vary their wot rpm with different trim and load. My own current boat is a much bulkier hull, but even that will vary by a good 500 rpm or more within the range of trim. The difference between 50 odd mph and late 60’s.
I think you will see massive gains by just switching to a laser 2 prop. Will give you a fair bit more lift than that vengeance and see good gains in rpm and mph.

 

[mike6868]

Doesn’t sound too bad with the numbers there. These kind of boats can wildly vary their wot rpm with different trim and load. My own current boat is a much bulkier hull, but even that will vary by a good 500 rpm or more within the range of trim. The difference between 50 odd mph and late 60’s.
I think you will see massive gains by just switching to a laser 2 prop. Will give you a fair bit more lift than that vengeance and see good gains in rpm and mph.

Merc Laser II in the same 21P?

 

[QBhoy]

I’d think so from your numbers. Although my instinctive initial thoughts were you would likely need a 23”....but i don’t know how you like to run the boat. With regards to weight in it, tweaked for out the home or top end etc.
Going by your numbers and assuming you have the boat trimmed up at that, you’ll see a good step towards ideal with a laser 2 of the same pitch. On similar boats here, the laser is the go to prop for these things. Give you more lift and hull out the water gaining rpm and efficiency. They are slightly more aggressive in terms of their dynamics compared to your own prop. They also show good all round character too. Many would consider the laser 2 as the best all rounder there is. Myself included.
I currently run an enertia on the boat, but I’m never selling the laser. It’s not quite as quick as the enertia but better all round, by a whisker. Perhaps only because my boat is a heavy bugger.
Boats like yours are known, tried and tested with the laser 2 and the big V6 Mercs. There ain’t a better combo perhaps.

 

[mike6868]

I’d think so from your numbers. Although my instinctive initial thoughts were you would likely need a 23”....but i don’t know how you like to run the boat. With regards to weight in it, tweaked for out the home or top end etc.
Going by your numbers and assuming you have the boat trimmed up at that, you’ll see a good step towards ideal with a laser 2 of the same pitch. On similar boats here, the laser is the go to prop for these things. Give you more lift and hull out the water gaining rpm and efficiency. They are slightly more aggressive in terms of their dynamics compared to your own prop. They also show good all round character too. Many would consider the laser 2 as the best all rounder there is. Myself included.
I currently run an enertia on the boat, but I’m never selling the laser. It’s not quite as quick as the enertia but better all round, by a whisker. Perhaps only because my boat is a heavy bugger.
Boats like yours are known, tried and tested with the laser 2 and the big V6 Mercs. There ain’t a better combo perhaps.

Thanks for all the great info! I was looking at both props that you recommended. Im leaning towards the enertia but was wondering if the info on the laser 2 is correct when they recommend it for engines 75hp to 115hp? Is it good for the bigger V6 mercs?

 

[QBhoy]

Thanks for all the great info! I was looking at both props that you recommended. Im leaning towards the enertia but was wondering if the info on the laser 2 is correct when they recommend it for engines 75hp to 115hp? Is it good for the bigger V6 mercs?

Yeah that can throw you a little. There are laser 2 for smaller outboards and laser 2 for the larger gear case outboards and mercruiser Alpha 1. Harder to come by these days in the latter.
Easy way to tell is that the even pitch numbers like 18” and 20” etc are all for smaller outboards. The odd like 19, 21, 23 etc are the larger outboards and Alpha one. It’s usuallt the rule with these props with the enertia being a bit of an exception. These come in one inch increments for Alpha and big outboards. Enertia an amazing prop. So too is the laser. I often switch between them depending on use. Enertia blisteringly quick but a bigger diameter and blade area so can have an effect low down the rpms. The laser also nearly as quick (depending on boat) but really shines as an all rounder. Good for cruising and water towing too in same pitch. Smaller diameter and blades.

 

[mike6868]

Yeah that can throw you a little. There are laser 2 for smaller outboards and laser 2 for the larger gear case outboards and mercruiser Alpha 1. Harder to come by these days in the latter.
Easy way to tell is that the even pitch numbers like 18” and 20” etc are all for smaller outboards. The odd like 19, 21, 23 etc are the larger outboards and Alpha one. It’s usuallt the rule with these props with the enertia being a bit of an exception. These come in one inch increments for Alpha and big outboards. Enertia an amazing prop. So too is the laser. I often switch between them depending on use. Enertia blisteringly quick but a bigger diameter and blade area so can have an effect low down the rpms. The laser also nearly as quick (depending on boat) but really shines as an all rounder. Good for cruising and water towing too in same pitch. Smaller diameter and blades.

Good to know! There is a pretty big price difference! I may just look for a used laser 2... And see how she runs

 

[QBhoy]

Good to know! There is a pretty big price difference! I may just look for a used laser 2... And see how she runs

Yeah. That’s the issue. They are so expensive...especially if you aren’t 100% it’s going to be the right pitch. The trusty laser 2 has been the go to prop for so many people over the decades. They are hard to come by here in good shape now. Certainly I’m never getting rid of mine. Dependable things.

 

[Sea Rider]

What's the min-max wot rpm range of that motor. If 6 K is the max, with 4200-4400 rpm motor in revving at the luging to middle side of the wot range as tested with current load. Plan adding more boaters ? Is hole shot fast enough ?

Can go at least one pitch down to say a 20 while maintaining same type of prop if it were a 3 blade alum or SS one to increase its wot range passing middle to max wot rpm range to improve hole shot if in need to do so.

It's much faster to go for a spot on prop maximization towards a less or more pitch prop when you already know the max rpm achieved on that current starter prop. If you change to other prop model that will be your second starter prop, very lucky if dials what you want on first try, if not will need to keep testing that same prop model in other pitches along spendiand more money.

Happy Boating

 

[Faztbullet]

What year 200 as it does make a difference....

 

[mike6868]

What year 200 as it does make a difference....

Older... Mid 80's power head, Mid 90's lower end