Merc Alpha4 no longer available. What to replace it with?

[achris]

Engine and boat details in my signature.
I was out last week and ate my 18" pitch 4 blade Alpha4 aluminium prop, to the point where it's not repairable. Just looking for help to select a replacement.

Full details.
With 19" (stainless steel) 3 blade Vengeance prop. Max revs - 4600, speed - 42 knots. But in the mid range it lacks 'pull', so I ran a 17" Vengeance until putting the Alpha4 (18") on.
With 17" Vengeance it would pull just on the rev limiter (4950) and about 40 knots. With the 18" 4 blade engine at rev limiter (4950) and around 38.5 knots.
I'm not too concerned about hitting the rev limiter as the weather here rarely allows WOT operations. I like the extra pull, and when the wind picks up the cruising speed drops the engine out of the power band with the 19".
So, with the Alpha4 NLA , I have the choice of the Spitfire (with odd inches of pitch) or the Revolution4 (also odd inches, but stainless).

Do I go the 17" or the 19"? Would love to hear from anyone who has used one of these and has comparison data between a 17" or 19" 3 blade and these 4 blades of the same pitch...

Cheers,

Chris

 

[dingbat]

My experience has been you loose 150-200 rpm going from Al to SS. Going from 3 to 4 blade can be crapshoot.

The difference between 14.25 x 17” Evinrude Offshore (4 blade) and the 15 x 17” Enertia (3 blade) was negligible.

Ended up dropping down to the 15” Enertia to pickup the 200 rpm I left on the table with 4 blade

Personally, I’d stay with a 17” and go with a prop with a bit more bite, ie Revolution 4

 

[Cortes100]

Took me quite a few trials but happy with the Spitfire performance. Here's some info on direct comparison with pitches.
Merc Black max 3 blade 21P.
Merc Spitfire 4 blade 21P.
Both props would just tag the rev limit at 4950.
Lost 1 mph on top speed with the spitfire (46+ mph GPS).
Pulling power was way better with the spitfire, through out the whole rpm range. The 3 bade almost felt sluggish.
Could easily get the 3 blade to wash out when doing sharp turns, NEVER happen with the spitfire.

 

[achris]

Took me quite a few trials but happy with the Spitfire performance. Here's some info on direct comparison with pitches.
Merc Black max 3 blade 21P.
Merc Spitfire 4 blade 21P.
Both props would just tag the rev limit at 4950.
Lost 1 mph on top speed with the spitfire (46+ mph GPS).
Pulling power was way better with the spitfire, through out the whole rpm range. The 3 bade almost felt sluggish.
Could easily get the 3 blade to wash out when doing sharp turns, NEVER happen with the spitfire.

Great info. Exactly what I'm looking for. Thank you.

 

[Stinnett21]

Will hope to go through the same process this summer. So achris let me get this straight. You actually increased pitch by 1 inch and added a blade and kept the same rpm going from the Vengeance to the Alpha4? Wow I would have never thought that! This really is a trail and error endeavor.

 

[Stinnett21]

Please report back on your results when you settle on one.

 

[achris]

Will do...

 

[Chris1956]

Turning point makes a 4 blade aluminum prop. It has 2 pairs of slightly different blades designed for for speed and power, respectively. I have one on my 21 footer w/150 HP Johnny. I like it much more than the TP Hustler I replaced with it, although I do not have the stats to back it up.

Thought you may be interested in checking it out.

 

[Stinnett21]

"...or the Revolution4 (also odd inches, but stainless)."

Cheers,

Chris

Just an fyi, according to Mercury's website the Rev 4 is also available in 18" and 20" pitches.

 

[achris]

I think that just for the smaller diameters.

Just an fyi, according to Mercury's website the Rev 4 is also available in 18" and 20" pitches.

 

[QBhoy]

Hi chris.
I think this is a tough one. Having only the vengeance to compare, I think isn’t doing the 3 blade props any justice. They are terrible props, to be honest. I’d urge you to try a tempest plus of the same pitch. You’ll find so much more grunt everywhere in the range and I’ll bet my life on it...better cruising attitude and 100% more top end. Better still, you’ll be taken just off that limiter by a little too. As for the Rev 4...they take a hellish lot of power to turn them well. Hit or a miss on boats like these. Honestly...try the tempest plus. Bigger diameter than usual 3 blades like laser and vengeance and come alive mid range and blistering top end.

 

[Fun Times]

It seems Merc suggests going up 1 inch according to the notes of the Alpha4 buyers guide.

Recommended for Inline 4, V-6, or V-8 gas sterndrives

Fits: Alpha drives, Bravo drives and Outboards 135 hp and above

The Alpha 4 is being discontinued. Mercury recommends the 4‑blade SpitFire propeller as the aluminum option for 90 CT ‑ 150 outboards and Sterndrive applications. When
transitioning to a SpitFire, increase 1" of pitch from the Alpha 4.

The Spitfire comes in RH (right hand, standard) rotation only. https://www.mercruiserparts.com/alpha-4

 

[Scott06]

I think that just for the smaller diameters.

Pretty sure it is available in inch pitch increments for the alpha drive , assumed you meant hub diameter not prop blade diameter.

if you liked the alpha 4 and are ok with aluminum try a michigan vortex 4 blade in the same pitch.i had very good results on my last boat with these. I think they were a very good value if you don’t need a shinny prop.

i don‘t have the apples to apples comparison you seek i run a 21” rev 4 on my current boat it definitely bites good and takes some torque to swing it as Q stated. If you go with the rev 4, go with the 17”, especially given some of your past comments about proping lower pitch to keep it responsive.

id stay away from the spitfire as i don't think it had enough blade area for a bigger , beamy, stern heavy boat like mine.

heres what i get on my 04 Sea Ray 200 sport , 3500 dry wt , 5.0 carb/ 1.81 drive stock except upgraded to edlebrock 1409.
4 blade 21" Vensura- 44 Mph, 4900-5000 rpm, 20% Slip, occasionally touch the limiter. Best holeshot.
3 blade 22" Enertia- 47 mph- 4850 ish rpm I think slip was like 14%, holeshot not as good as vensura or rev4
4 blade Revolution 4- 48 mph 4900 rpm - I think slip is 12%, real nice hole shot with medium PVS plugs. Biggest difference on top end the rev4 has enough bite to really trim up and gets ab out 3-4 mph more vs max trim I could run for the Vensura. Engine will get another 300 rpm when really trimmed up and the prop is near the surface. If i had a 5.7 i think it would be enough to swing this better in holeshot.
23” spitfire i basically got the same rpm/ speed results as the vensura but slip was ludicris Given more pitch. Only ran this a couple times cause basically didnt work for me, oversold in terms of marketing vs performance reality. I keep it for spring use when the water is high and has a lot of logs in it...

 

[Stinnett21]

Scott, just so we can compare I think you left off the pitch of your Rev 4. Also, why such steep pitch on the Spitfire? Doesn't seem fair to that product.

 

[QBhoy]

Pretty sure it is available in inch pitch increments for the alpha drive , assumed you meant hub diameter not prop blade diameter.

if you liked the alpha 4 and are ok with aluminum try a michigan vortex 4 blade in the same pitch.i had very good results on my last boat with these. I think they were a very good value if you don’t need a shinny prop.

i don‘t have the apples to apples comparison you seek i run a 21” rev 4 on my current boat it definitely bites good and takes some torque to swing it as Q stated. If you go with the rev 4, go with the 17”, especially given some of your past comments about proping lower pitch to keep it responsive.

id stay away from the spitfire as i don't think it had enough blade area for a bigger , beamy, stern heavy boat like mine.

heres what i get on my 04 Sea Ray 200 sport , 3500 dry wt , 5.0 carb/ 1.81 drive stock except upgraded to edlebrock 1409.
4 blade 21" Vensura- 44 Mph, 4900-5000 rpm, 20% Slip, occasionally touch the limiter. Best holeshot.
3 blade 22" Enertia- 47 mph- 4850 ish rpm I think slip was like 14%, holeshot not as good as vensura or rev4
4 blade Revolution 4- 48 mph 4900 rpm - I think slip is 12%, real nice hole shot with medium PVS plugs. Biggest difference on top end the rev4 has enough bite to really trim up and gets ab out 3-4 mph more vs max trim I could run for the Vensura. Engine will get another 300 rpm when really trimmed up and the prop is near the surface. If i had a 5.7 i think it would be enough to swing this better in holeshot.
23” spitfire i basically got the same rpm/ speed results as the vensura but slip was ludicris Given more pitch. Only ran this a couple times cause basically didnt work for me, oversold in terms of marketing vs performance reality. I keep it for spring use when the water is high and has a lot of logs in it...

Scott. What pitch was that rev 4 that managed quicker than the enertia. Would love to see a tempest plus of same pitch on your boat and see how it goes. I’ve been amazed with the Tempest so far.

 

[QBhoy]

I’ve got a comparison that’s relevant. Posted it before I’m sure.
regal 1900 stepped bowrider
4.3 mpi alpha
21” spitfire 4 blade ran to the limiter at about 4950 at 48 mph from memory.
The owner was about to order a 21” stainless 3 blade thinking he would be about right. In the meantime he tried out my outboard cuddy boat’s tempest plus 19” for the hell of it. I was taken back by the result. Not what I expected.
19” tempest plus ran to about 4850-4900 rpm at 52/53 mph from memory. Amazed to see the rpm drop over a 21” ally 4 blade. Despite the bigger diameter tempest and being stainless...you still wouldn’t imagine it would drop the rpm off the limiter (like spitfire was on) and also see a gain in speed. She accelerated better too. Had a lovely cruising rpm of about 2500 rpm and happy there in the 20’s. Amazing.

 

[Stinnett21]

No matter what performance goal I input Mercs prop selector never mentions the Tempest Plus for me. Is it a rather new prop? Maybe only targeted for outboards.

 

[QBhoy]

No matter what performance goal I input Mercs prop selector never mentions the Tempest Plus for me. Is it a rather new prop? Maybe only targeted for outboards.

I wouldn’t pay too much attention to the prop selector. It makes a good effort for very general advice...but it can’t possibly know how your particular boat will perform. The tempest is made for a range of set ups. I ran a tempest on my inboard v8 for a day. I knew it was too little pitch, but was amazed what it did manage up until the limiter was hit. It’s the prop that has replaced the laser 2 of old. Great mix of abilities

 

[QBhoy]

No matter what performance goal I input Mercs prop selector never mentions the Tempest Plus for me. Is it a rather new prop? Maybe only targeted for outboards.

What boat and engine do you have now ?

 

[Stinnett21]

Well I should start another thread for me. Let's see what Chris comes back with.