Let's Talk Propellors

juggernaut1

juggernaut1

Well-Known Member
Apr 19, 2015
1,152
Perth, Western Australia
Boat Info
Boatless - sold Searay 38 Sundancer
Engines
8.1’s
I'm considering the idea of upgrading the props on my 38 to Veems (as they are local) and have the following questions if anyone is able to assist:

The 2006 Sea Ray parts list for my boat shows the following - is this suggesting that there is a different pitch for left and right props? If so, why?

PROP, 21"X 22.5"X 4.85"X 1.5" R4BC NIBRAL MIK
(TVD-8.1 S HORIZON (T-370 PHP) MCM INBOARDS)
(TVD-8.1 S HO (T-420 PHP) MCM V-DR. INBOARDS)

PROP, 21"X 23"X 4.85"X 1.5" L4BC NIBRAL MIKAD
(TVD-8.1 S HORIZON (T-370 PHP) MCM INBOARDS)
(TVD-8.1 S HO (T-420 PHP) MCM V-DR. INBOARDS

What is the clearance from shaft to hull for my boat (yes I could dive overboard - but the boat is not local)? Veem works on a clearance of 12 to 15% to determine max prop size.

What is the shaft taper for my boat - does Sea Ray have a standard?

What WOT rpm should I be seeking to achieve - 4600 rpm? When I ran the boat a few weeks ago at WOT in the open ocean with all our gear on board (we live on it on the weekends), 9ft6" dingy on front deck/half fuel/full water it turned circa 4,716 rpm (port)/ 4,666 rpm (starboard) at 29.5 knots per the smartcraft. I note that Boattest achieved 4,750 at 30.2 knots when this boat was originally tested.

At what rpm does the 8.1S Horizon develop peak HP.

Can anyone link to a dyno for this motor?

Has anyone had experience with 5 blade props as this is what the Veem on-line prop selector is suggesting for a "desired" speed of 30 knots at 4,600 rpm. Plugging in a "desired" speed of 32 knots at 4,600 rpm, it suggests a 4 blade. Note that these recommendations are subject to verification by a naval architect at Veem.

Any other comments/considerations I should take into account?
 
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As to the difference in pitch between the port and stbd props, Sea Ray used a certain ZF transmission in some 34-38 ft Sundancers with 8.1 engines that had a fairly large difference in final drive output ratios in forward and reverse. This is important because one gear runs in forward; the other in reverse since you do not have counter rotating engines. There isn't enough information in your profile to look this up for you, but you can get the complete transmission model number and stated ratio off the mfg's plate on your transmission, then go to the ZF website and look up the specs on that transmission and then check the final drive out put ratios in fwd and reverse to verify if your boat has enough difference to need a different pitch on the port and stbd.

Given the parts listing for the boat, I suspect you do have one of those transmission models.
 
Thanks Frank - you are indeed correct. I run the ZF 63IV in the "2.5:1" ratio and there is a spread on the "forward" and "reverse" (as there is on the other ratios).

http://www.sbmar.com/docs/ZF/DS-ZF_63_IV.pdf

I also emailed Sea Ray support yesterday afternoon re props for my boat and this morning I find the serial number sheet in my inbox confirming the different pitches. On that note hats off to Sea Ray for getting back to me so quickly - clearly a company who cares about the owners of their boats :smt038.
 
Hi Fella's,

I just want to revisit my thread and get some sort of consensus as to what rpm's I should be looking at achieving when re propping. Per the manual WOT rpm should be in the range of 4,200 to 4,600. I took my boat out again a couple of weeks ago and achieved 31.5 knots and 4949 rpm port and 4882 rpm starboard with 1/3 fuel, full water, full gear, inflatable on the bow in calm coastal conditions, with possibly a hairy bottom. See here.

http://clubsearay.com/showthread.php/8807-Post-Your-Top-Speed/page6

What I plan to do is take the boat out again and see what she runs go back and refuel and go out again and she what she runs all on the same day and same conditions to see what fuel load does to rpm and to obtain the "spread" of speed and rpm's. I will already have full water, inflatable and full gear onboard.

Let's say for arguments sake the spread is 300 rpms. Armed with info what should I be theoretically specifying as my WOT rpm full loaded:

A) 4500 lightly loaded / 4200 fully loaded; or
B) 4600 lightly loaded / 4300 fully loaded; or
C) 4700 lightly loaded / 4400 fully loaded; or
D) 4800 lightly loaded / 4500 fully loaded; or
E) 4900 lightly loaded / 4600 fully loaded; or
F) Some other rpm?

Of course the 300 rpm spread is pure conjecture at the moment but any guiding principles would be appreciated at this time.

I am probably going with Veem props and they want to know the absolute fully loaded (not typical load) WOT rpm when specifying props for the boat.
 
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Curious to know how the veem prop upgrade went? I have a 2007 38 and I’m considering doing the same. Any input would help. Thx
 
From what I have been seeing with Searay they are under propped it seems. I had worked on mine a few times to get them where I want and ended up going up one pitch size and 2 cup sizes from factory. I was still able to get my 4600 rpm and that's with 8 people on board and 3/4 fuel. Here is my thread. Different boat then yours though, but same difference ( Well now I have to start all over since I hit a rock last weekend :( )
 
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Ouch! Sorry to hear that. Veems recommended I go with a 20” prop which is down from my 21’s but a small increase in pitch. I’m just looking to increase my cruising speed a little without sacrificing my economy to much. I cruise around 3650 rpm @ 23 mph.
 
Gordon Jukes said:
Curious to know how the veem prop upgrade went? I have a 2007 38 and I’m considering doing the same. Any input would help. Thx
Click to expand...
Gordon Jukes said:
Ouch! Sorry to hear that. Veems recommended I go with a 20” prop which is down from my 21’s but a small increase in pitch. I’m just looking to increase my cruising speed a little without sacrificing my economy to much. I cruise around 3650 rpm @ 23 mph.
Click to expand...

I haven't got the Veems....yet.

For the time being I added an inch of pitch to my existing props and was pretty happy with the improvement. The guy that repitched my props did say the Veems would be superior in speed, smoothness and economy. He also mentioned the Teignbridge props were fairly thin. I also enquired about the ACME props, but the Veems are cheaper, and made locally

Before sea trialling my existing props for the Veems I wanted to soda blast the hull and redo my antifoul so as to start with a fresh bottom. Due to demand I couldn't get this done last year but will try and arrange it this year.
 
Thanks for the reply. I’ve been hearing great things about the veems but not from anyone with first hand knowledge.
I think I’ll pull the trigger and give them a shot
 
I’ve just been flirting with the veems prop calculator so far. It recommended the veemstar C which I don’t believe uses the strips. it also suggest going down to a 20” prop from 21 and an increase in pitch
 
Veemstar C can be had with or without the interceptor strips.

My prop guy recommended staying with the 21 inches despite the calculator also showing 20 inches for me too. He also recommended the Veemstar over the Veemstar C. Veemstar C shows speed range of 28 to 50 knots which I’m not sure is applicable to our boats.
 
I heard the same as well. It’s getting a little confusing to say the least. Was hoping to hear some first hand experience. so what will you end up going with when you change?
 
Gordon Jukes said:
I heard the same as well. It’s getting a little confusing to say the least. Was hoping to hear some first hand experience. so what will you end up going with when you change?
Click to expand...

I’m not sure what I’ll go with just yet. I’ll likely speak to my prop guy and Veem when I’m about to buy.

I the reason Veem suggests a smaller prop is to create more clearance between the prop and hull for ultimate smoothness. Their prop calculator originally suggested a 5 blade prop for mine for this reason too. After speaking to them at the time their naval architect was of the opinion a 4 blade would be fine on this diameter prop.

Interestingly, ACME suggested a 3 blade prop for our boats for best performance.
 
juggernaut1 said:
I’m not sure what I’ll go with just yet. I’ll likely speak to my prop guy and Veem when I’m about to buy.

I the reason Veem suggests a smaller prop is to create more clearance between the prop and hull for ultimate smoothness. Their prop calculator originally suggested a 5 blade prop for mine for this reason too. After speaking to them at the time their naval architect was of the opinion a 4 blade would be fine on this diameter prop.

Interestingly, ACME suggested a 3 blade prop for our boats for best performance.
Click to expand...

I believe, a 3 blade = better performance but a 4 blade = better handling around the dock, better economy and allows lower planning speeds.
 
techmitch said:
I believe, a 3 blade = better performance but a 4 blade = better handling around the dock, better economy and allows lower planning speeds.
Click to expand...

That’s my understanding too. I’m also on the Riviera Facebook forum and those that have gone from 4 to the 5 blade Veems, report better fuel economy and smoothness again compared to the 4 blade props.
 
Soooo, after a lot of back and fourth with veems and their prop guru. Their now recommending a 4 blade 23x22. Vermstar LC.
 
5 blade props have to be pretty pricey.
FFE34259-17AA-4882-AFE4-87EF21070032_1_201_a.jpeg
 
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