Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

[Tom61]

Hello,

I'm new to the forum and also to stern drives. I recently purchased a 2001 Sea Ray 180 bow rider with a 3.0 Mercruiser I/O. I bought it this winter and haven't had it in the water yet. It has an aluminum Mercury 14 1/4" 21 pitch prop on it with some dings and dents. The guy I bought it from also gave me a Quicksilver Mirage 15 1/4" 19 pitch stainless prop for it but it has never been run on the boat.

My question is if the Mirage SS prop will fit the shaft and if the extra inch larger in diameter will physically fit without interference? Also, will it run ok on the boat? I'm just looking for a general purpose prop since I won't be doing a lot of skiing or water sports and mostly cruising.

Thanks for your help.

Tom

 

[chris.j.marshall]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

I don't know the answer to your diamater question; I'd suggest putting it on the shaft and spinning it by hand. 21 seems like a lot of pitch for a 3.0. I've always run a 19 on my 17 footer, planes quickly and suits my needs well.

 

[jestor68]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

The Mercruiser Alpha 1 drive can take up to a 16" diameter prop. If your stern drive has a fin anode, it may be necessary to change it for clearance. Mercury sells a special anode for that purpose.

So yes, it will fit. It should perform OK; but a water test is the only way to be sure to see that the motor operates within it's 4400-4800 rpm range at full throttle.

 

[tazrig]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

+1^^^

 

[dan02gt]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

A 21P is standard for most 3.0L bowriders. If you want more pulling power and a better hole shot dropping down to a 19P will definitely help. However, the Mirage is not really the prop you want on that boat. It's designed for big block powered go fasts and your little 3.0 it not going to perform the best with it. Sell it and pick up something else. Check out Mercury's prop selector for some good recommendations Prop Selector | Mercury Marine

 

[MikDee]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

A Mirage is a great prop, it should normally fit right on the shaft no issues. I suggest you try it (being as you already have it as a gift) to get a feel for how a rigid stainless prop will give you more solid thrust at all speeds. It will almost feel like "cruise control". If it does not bring you into full rpm range, don't push it, & lug the boat, but it will do fine with no damage running at any rpm under top rpm. That's what I would do.

If you richened outward your idle mixture screw and maybe got a little faster (stronger) idle, & ran synthetic oil in your engine, it is more slippery, (less friction) then regular oil, and you might pick up a few hundred rpm at WOT, to put you in range of the Mirage. But, I disavow any knowledge of this last statement!

 

[4now04]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

If the 21p prop is stock, I think you will find that the 19 ss prop will give good acceleration, but you will probably loose top end and may be exceeding the max recommended rpm. The diameter is probably more than you need. You might look at trading for a 14.25 x 21 ss prop and have the aluminum prop reconditioned. The true test will be to see how it performs this spring when you take it out.

 

[Tom61]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

Thanks for the replies. That helps a lot.

Much appreciated,

Tom

 

[dazk14]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

I am repeating pieces of much of the above.

The Mirage will fit without any anode modifications.

The only reason to put the Mirage on is that you own it...and it's shiny.

It is one of the worse performance props you could put on a 3.0 18' bowrider. Even against your aluminum, you will lose top end.

Fortunately, that is a common size for the big cruisers and offshore boats, so you'll get good money for it used. I'm presuming here it's a mirage Plus?

A nice cruising prop with good performance/economy/load carrying capacity/easier docking/good tracking in rough water... would be a Stainless Solas HR4 Titan 14-1/8 x 19" 4 blade $290, but we would need your current performance data to confirm.

I think you could also find lots of used 3 blade 19/20" 14"ish diameter stainless props on ebay.

However, try what you've got. There's never any certainty, only probability, when it comes to props.

 

[Tom61]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

I am repeating pieces of much of the above.

The Mirage will fit without any anode modifications.

The only reason to put the Mirage on is that you own it...and it's shiny.

It is one of the worse performance props you could put on a 3.0 18' bowrider. Even against your aluminum, you will lose top end.

Fortunately, that is a common size for the big cruisers and offshore boats, so you'll get good money for it used. I'm presuming here it's a mirage Plus?

A nice cruising prop with good performance/economy/load carrying capacity/easier docking/good tracking in rough water... would be a Stainless Solas HR4 Titan 14-1/8 x 19" 4 blade $290, but we would need your current performance data to confirm.

I think you could also find lots of used 3 blade 19/20" 14"ish diameter stainless props on ebay.

However, try what you've got. There's never any certainty, only probability, when it comes to props.

Thanks for the response. Unfortunately, it's just a Mirage and not a Mirage Plus. I think I'll throw it on eBay or Craigslist and just go with a new, stock aluminum prop. For what I'll be doing, it should work fine.

Thanks again.

Tom

 

[dazk14]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

Geez, if I thought that I might talk you out of trying it, I would have kept my trap shut.

A Mirage is a fine Prop.

You'd be crazy not to try it on your boat.

If you can pull your numbers and are primarily cruising, you might like it.

 

[fishrdan]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

I'd give the 19P Mirage a try, but think the 15" diameter isn't going to work well with the 3.0L. You all ready have the prop, so you don't have anything to loose trying it out.

How are you satisfied with the boat's performance with the current prop?

 

[Texasmark]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

I'd try it too just for a data point. A lot of SS props are designed for a specific purpose and most have refinements that alum can't/doesn't usually deliver. How long does it take to try? Not very long. Besides, whatever you decide to run, until you "run it" you are just guessing at the results! Answer to running this prop and comparing it's attributes to one you contemplate buying can help you make a better "guess" on the new one.

My 2c,
Mark

 

[Tom61]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

Geez, if I thought that I might talk you out of trying it, I would have kept my trap shut.

A Mirage is a fine Prop.

You'd be crazy not to try it on your boat.

If you can pull your numbers and are primarily cruising, you might like it.

It's not a big deal. I might hang on to it and give it a try. It doesn't cost anything but a little time to switch it out and give it a try.

I'd give the 19P Mirage a try, but think the 15" diameter isn't going to work well with the 3.0L. You all ready have the prop, so you don't have anything to loose trying it out.

How are you satisfied with the boat's performance with the current prop?

I just bought the boat this past November. I brought it home and winterized it so I haven't had it in the water other than when I test drove it. It seemed fine then with the stock prop but I didn't spend a lot of time in the water with it.

 

[gm280]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

Just remember, everybody needs a spare prop. And if your present aluminum prop is dinged up, have it repaired and it will be as good as any new aluminum prop. So maybe you should have your older prop repaired and keep both... JMHO!

 

[Texasmark]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

Just remember, everybody needs a spare prop. And if your present aluminum prop is dinged up, have it repaired and it will be as good as any new aluminum prop. So maybe you should have your older prop repaired and keep both... JMHO!

Well, almost. The shops that repaired mine before I went to the OMC SST back in 1973 did a sloppy job of painting to the point where half the repair was exposed on the first outing. So here I had this nice new boat with this POS (tuff) looking prop. Mechanically the restorations were fine. For a spare prop, why bother with fixing it up. To me a spare is to get you home and a dinged up prop usually is capable of that. But that's personal opinion.

Mark

 

[phillnjack2]

Re: Can I go from a 21 pitch aluminum to a 19 pitch stainless prop?

a 21 inch pitch alloy prop is only about 19 inch when put under strain.
the 19 pitch stainless will be perfect swap for similar results to what your getting now.
BUT what you need to know is are any of the props cupped at the moment, cupping adds around an inch to pitch.
the extra bit of diameter wont make a great deal of difference to a 3 litre engine, if it does then have it turned down a touch and try it.
don't go getting it cut all the way down if you pull tubes around, as this will be better for low down torque.
if for any reason the pull away is not good enough just have it vented, 3 nice 1/2 holes will do the job and give you a great pulling prop.

A Friend once had a searay 180 with a 4 pot 3 litre and used 13 1/2 x 23 pitch, he used it for all sorts too.

phill