New SS Prop Questions

[Gary GAS]

We have a 2008 Blue Water mirage 19 ft. bow rider with a volvo 4.3 v6 190 hp. carbed engine with the sx drive with 1,78 gear drive. Was thinking about getting a solas Rubex HR-4 ss 4 blade prop to replace the alum. solas 4 blade amita prop we now have. This little boat has a vented type hull and rides bow high without any trim and needs the four blade props for the added stern lift. I have added a set of bennett adjustable trim tabs that can take care of the problem when needed or balance the ride also. The amita 4 is a 19 pitch 4 blade and tops out at 45 mph with by gps and top rpm,s at the speed is 4860 buy my snap on shop tach, and 4950 rpm with the boats tach. That is with two guys at about 220 lbs each and a full tank of gas and std. gear on board. I have also used a merc spitefire 4 blade prop at 21 pitch that runs 4720 rpms at 47 mph gps. They say the spitefire 4 blades run about the same as a 3 blade prop as far as rpm,s go. The spitefire works the best all around.The rpm range on the motor I think is 4200 to 4600 rpm and the same merc. motor is 4400 to 4800 so I ,am right at or a little above the top limit. What do you think of the solas rubex HR-4 prop and should I go with a 19 or 21 pitch prop??. I know the ss have a little more rake and cupping and thinner blades and once you buy it on line you own it so I was looking for some input from you guys We do most of our boating here in Oregon at the 2000 ft. elevation and the four blabe props work all around best on the boat. Thank you for your replys

 

[Scott06]

I this in if you look on line your wot is 4400-4800 same as merc as its the same base engine. I think the pitch depends on how you use the boat. If you plan on more water sports or tend to go out full of people stay with a 19", otherwise you said the 21" is best all around. What specific improvement are you seeking in upgrading props

 

[Texasmark]

Can't comment on 4 stroker rpms vs 2 stroker where I always ran mine at or just above max rated with my "regular" boat load of folks and gear. Running high rpms with 2 guys says to me that you are propped right where you want to be.....just back off the throttle when running light if excessive rpms bother you. That way you have the dig you need for the performance you want when you load up the boat. I think you are right on with your tabs and 4 paddles.

No experience with your shop tach but if your boat tach is Quicksilver or Mercruiser I would expect it to be closer to correct.....besides what's a couple hundred at 4k? 10% tolerance which used to be the norm back in the day is 400 and the gauges tolerance could include that.

 

[Gary GAS]

Looking to improve top speed and add stern lift that is way I was thinking of going to a ss prop. In my case with the solas rubex HR-4 four blade to you think the 19 0r 21 pitch would be best?? I like the price of these prop that is why the rubex HR-4. Do you think there is a better choice in props for a good price??

 

[Texasmark]

Looking to improve top speed and add stern lift

Two opposites simultaneously? To improve speed the hull must come out of the water to reduce drag for a given propulsion system. If you have a deep V, high deadrise at the stern, I/O, for a hull example, I can see where you want stern lift to get the boat up and out of the water, leveling off the angle of attack on the water allowing for less wetted hull, less drag, and more speed.

Shallow pitched, multiblade props do that with engine trim....prop doesn't have to be SS. General purpose prop and trim tabs would be a better solution, hydraulically actuated tabs would provide the best performance to use to get out of the hole and once out, lift them up for top speed.

On a different hull design, like a high powered, padded hull bass boat, a high performance (ported) SS prop and trim are the things and a high rake prop (blades bent back from the root to make a tube of the thrust area) to get the bow up and the boat on the pad which is like having a 3000# boat on a water ski (for amount of drag produced).

 

[Scott06]

The four blade will help stern lift , if speed is the goal stay with a 21". With out trying a bunch of props on your boat hard to say if one prop or another is best for your exact rig.the HR4 is probably just as good as another as 4 blade. I would expect a modest increase in performance vs the spitfire, but not a whole lot will be interested to see what it does for you.

Best way to really answer your question is to find a prop shop that will let you demo several types and pitches. I have a somewhat local guy who does it, the are some on line who also will do the same.

 

[Gary GAS]

Thank you all for your input

 

[Texasmark]

The four blade will help stern lift , if speed is the goal stay with a 21". With out trying a bunch of props on your boat hard to say if one prop or another is best for your exact rig.the HR4 is probably just as good as another as 4 blade. I would expect a modest increase in performance vs the spitfire, but not a whole lot will be interested to see what it does for you.

Best way to really answer your question is to find a prop shop that will let you demo several types and pitches. I have a somewhat local guy who does it, the are some on line who also will do the same.

I always recommend that as the correct answer. Will cost you more initially, but you can get it right the first time and guess what: When your money is spent, it's gone forever. What stays with you is what you bought with that money. Wink!