Going from 4 blade aluminum to 4 blade SS

[reidc15]

My boat is a 1995 Genesis 1810 Ski/Fish with 135 hp inline 4 Mercruiser 3.0 Alpha One 2.0 gear ratio. I am currently running a 20" pitch 4 blade aluminum prop (I think Alpha 4) getting the following results at WOT (4400 - 4800)...

Boat Tach RPM - 4550
GPS Speed - 37 MPH

These results were taken with only me and in the boat. Usually there is another person with me and very rarely three or four and skiing or tubing. This boat is used for mostly fishing and mid range cruising in the 2800 to 3000 rpm range running about 22 mph (maybe WOT for 30 seconds to see how engine is performing). I am looking at buying a Solas HR Titan 4 blade prop and through reading these forums want to make sure I am doing this correctly.

Is it necessary to drop 1" going to SS since my motor is small?
Drop 1" to raise rpm 150-200 rpm to get closer to max 4800 rpm
Do I drop another 1" for the extra cupping of the Solas SS prop and the occasional extra passengers in boat?
Which pitch Solas prop would be better for my application 17, 18, or 19? I am leaning towards the 18" but have read great reviews about the 19" and 3.0 motor.

 

[Texasmark]

Re: Going from 4 blade aluminum to 4 blade SS

I didn't go through all your numbers. Just my suggestions: Alum has a lot of "sins". SS has few. Also, SS usually has additional refinements that make it all together different than an alum prop. You have to go through the differences one by one and see what it does to performance on your boat under your operating conditions. Don't expect a text book answer as there are none...... the correct one. Only way you know what works for you is to run it.

Go to to a dealer, prop shop, that will loan you a prop till you find what is right for you. Follow his rules...run it just to get the numbers and bring it back.....no dings etc. You may pay 50% more than a SWAG from an online store but in the long run it will be the best investment......I have 4 props for my engine, running up to about $1000 to get the right answer.........I didn't go to a dealer. I SWAGGED it off the internet. Get the drift?

Think about it.

Mark

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

Fair enough...just thought there was some general rules I could go by when changing props. Does anyone have any experience using the Solas SS Titan 4 blade on a mercruiser 3.0? Is this a good prop for I/O? If no can another brand be recommended that is more suited for this motor?

 

[jestor68]

Re: Going from 4 blade aluminum to 4 blade SS

Since the HR Titan is a more aggressive design than your aluminum prop, I'd say to go with the 18 pitch Titan.

I doubt that you'll see as much rpm increase as you think due to the aggressive design of the HR Titan. It will definitely be better at pulling and/or load carrying.

 

[fishrdan]

Re: Going from 4 blade aluminum to 4 blade SS

Drop 1" to raise rpm 150-200 rpm to get closer to max 4800 rpm

You could do that right now with an aluminum prop, to get closer to the top end of the engine's WOT range. I want the engine running at the top end of it's WOT range while lightly loaded, so it's (hopefully) still within the WOT range while heavily loaded.

The big question is, what is the WOT RPM with the a boat load of passengers skiing/tubing? Will the engine hit 4,400RPM, low end of the WOT range?

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

That was what I was thinking...drop 1" pitch and stay with aluminum 4 blade is the safest bet or take a chance with the Solas SS Titan 18" pitch. Thanks for the input guys!

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

Update...purchased the Solas SS Titan 18" form Iboats and tried it yesterday in windy choppy conditions with the following results:

4650 rpm
37 mph

I think these numbers would improve to at least 4700 rpm and 38 mph under more favorable conditions. The first thing I noticed about the Titan prop was the quick response time from throttle to boat movement. It seemed as though the carburetor and prop were more connected. This prop also raised the stern at cruising speed (23 mph and 3000 rpm) for a smoother ride and excellent handling. Hole shot was great and planes quickly. I have owned this boat for 19 years and did not realize what I was missing with a stainless prop! My little inline 4 has transformed into a V6 using this prop. Hope this helps anyone thinking about changing from aluminum to a stainless prop.

 

[fishrdan]

Re: Going from 4 blade aluminum to 4 blade SS

This prop also raised the stern at cruising speed (23 mph and 3000 rpm) for a smoother ride and excellent handling. Hole shot was great and planes quickly.

I don't think the SS aspect of the prop is giving you most of those characteristics, it's the 4-blade design (IE: stern lifting). I had the same experience when I installed an 18P Alpha4 (aluminum) prop on my boat, much better performance all around compared to the 3-blade it replaced.

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

fishrdan, I previously had a 4 blade aluminum (not 3 blade) 20" pitch alpha 4 prop and switched to a Solas SS HR Titan 4 blade 18" pitch. I think it is the combination of the extra cupping and the SS prop not flexing during throttle advance that has made the biggest difference.

 

[fishrdan]

Re: Going from 4 blade aluminum to 4 blade SS

fishrdan, I previously had a 4 blade aluminum (not 3 blade) 20" pitch alpha 4 prop and switched to a Solas SS HR Titan 4 blade 18" pitch.

Whoops, that's what I get for not reading what you had posted, didn't pick that up... Good to hear the new prop is working better than the Alpha4, it will be interesting to see what the boat does in better conditions.

 

[dazk14]

Re: Going from 4 blade aluminum to 4 blade SS

Did you trim out until it ventilates? I realize conditions may not have allowed for it, I'm surprised your not seeing more top end.

Please report back when you have more test data...

Are you using a doel fin, etc..?

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

I do have a fin on the back...not sure what brand it is (it's been there for 19 years). I adjusted my trim to specs of 21 3/4" (it was at 20 1/2" and my previous prop would ventilate @ full trim) before adding the new prop because I read where the Titan should run higher in the water. I did trim all the way out and noticed very little ventilation and trimmed back down just a touch to achieve the grip. I never saw the rpms go higher at top trim like the aluminum prop did but it just sounded and felt like I needed to touch it down barely. I was out again today but it was still a little windy and the numbers were about the same. Dazk14, are you thinking I should see more rpms or mph?

 

[jestor68]

Re: Going from 4 blade aluminum to 4 blade SS

I do have a fin on the back...not sure what brand it is (it's been there for 19 years).

If it's not the Doel Fin, it might be the wrong one.

Regardless, the prop is the correct one. Don't change anything.

 

[dazk14]

Re: Going from 4 blade aluminum to 4 blade SS

I do have a fin on the back...not sure what brand it is (it's been there for 19 years). I adjusted my trim to specs of 21 3/4" (it was at 20 1/2" and my previous prop would ventilate @ full trim) before adding the new prop because I read where the Titan should run higher in the water. I did trim all the way out and noticed very little ventilation and trimmed back down just a touch to achieve the grip. I never saw the rpms go higher at top trim like the aluminum prop did but it just sounded and felt like I needed to touch it down barely. I was out again today but it was still a little windy and the numbers were about the same. Dazk14, are you thinking I should see more rpms or mph?

A little more speed. The RPM's are great. The Titan has great geometry and rake. Value and performance wise, Jestor was spot on.

Trimmed out, I thought you would see 2-3mph improvement.

If your bored, you may want to try it without the fin. They often times scrub off speed. You don't have to worry about the holes.

Jestor, Besides supporting Mr Doelcher, the original inventor, what are you thinking when it comes to all the Doel-Fin copycats being the wrong one?

 

[Moose_25_2500]

Re: Going from 4 blade aluminum to 4 blade SS

Update...purchased the Solas SS Titan 18" form Iboats and tried it yesterday in windy choppy conditions with the following results:

4650 rpm
37 mph

I think these numbers would improve to at least 4700 rpm and 38 mph under more favorable conditions. The first thing I noticed about the Titan prop was the quick response time from throttle to boat movement. It seemed as though the carburetor and prop were more connected. This prop also raised the stern at cruising speed (23 mph and 3000 rpm) for a smoother ride and excellent handling. Hole shot was great and planes quickly. I have owned this boat for 19 years and did not realize what I was missing with a stainless prop! My little inline 4 has transformed into a V6 using this prop. Hope this helps anyone thinking about changing from aluminum to a stainless prop.

What was the prop size of your aluminum and new SS Titan? I have the same engine and also looking at upgrading my prop. Thanks

 

[dazk14]

Re: Going from 4 blade aluminum to 4 blade SS

What was the prop size of your aluminum and new SS Titan? I have the same engine and also looking at upgrading my prop. Thanks

Read post #1 and post #7. The numbers are labeled in upper right corner of each post.

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

Deleted post

 

[reidc15]

Re: Going from 4 blade aluminum to 4 blade SS

A little more speed. The RPM's are great. The Titan has great geometry and rake. Value and performance wise, Jestor was spot on.

Trimmed out, I thought you would see 2-3mph improvement.

If your bored, you may want to try it without the fin. They often times scrub off speed. You don't have to worry about the holes.

Jestor, Besides supporting Mr Doelcher, the original inventor, what are you thinking when it comes to all the Doel-Fin copycats being the wrong one?

I took off the stingray fin and did not see any changes at WOT. What I did see was bow rise while getting on plane and a little higher bow while on plane so the fin went back on and everything is back to normal. I am going to try the SE Sport 300 this weekend (same bolt pattern) since it doesn't have the turned down rear that the stingray has and seems to have good performance reviews.

 

[Moose_25_2500]

Re: Going from 4 blade aluminum to 4 blade SS

Read post #1 and post #7. The numbers are labeled in upper right corner of each post.

I do see that you list the Pitch for th aluminum as 20" Pitch and 18" Pitch for the SS but I do not see where you list the Props Diameter. Thanks

 

[dazk14]

Re: Going from 4 blade aluminum to 4 blade SS

I took off the stingray fin and did not see any changes at WOT. What I did see was bow rise while getting on plane and a little higher bow while on plane so the fin went back on and everything is back to normal. I am going to try the SE Sport 300 this weekend (same bolt pattern) since it doesn't have the turned down rear that the stingray has and seems to have good performance reviews.

The stingrays do sit back pretty far off the AV plate, so your trim must be lifting the whale tail rear portion out pretty well.

If it's not slowing you down, not sure why the switch, but you're not risking much dough. Unless your thinking acceleration.

Can you post the diameters for moose, so I don't have to go look them up. Thanks