55 Sea Ray with 3408 800 Cat's prop question

55 Sea Ray R · Nov 30, 2021

I have 4 blade props at 80% ideal conditions I am seeing 26.5 Knots. WOuld a 5 blade perhaps up that number ?

DOCKMASTER · Nov 30, 2021

Doubt you would see much gain. Maybe a smidge if you run stern heavy and already using full trim tabs. You get a bit of added stern lift from 5 blade vs 4.

More importantly, what is your current rpm at WOT with full load (fuel, water, etc) and what are you rated at? In other words, are you propped correctly to begin with?

55 Sea Ray R · Nov 30, 2021

Hit the limiter 2350 but not by much. It could use a bit of lift on back I have two saddle tanks 200 each. I also have a center tank 300 that starts at the end of the saddles. I run it out first and I would say I pick up 2 knots by the time I switch. Which is usually at half so the genset doesn't run out.

motoryachtlover · Nov 30, 2021

My experience with switching to 5 bladed Veems from 4 bladed Michigans was a slight increase in cruise speed and a drop in top end. The 5 blades were smoother and the hole shot was better. Fresh off a bottom job with clean propellers I can get 2450 at full throttle. My point is I am purposely under propped and most likely loosing some performance. Going downhill with all environmental factors in my favor I would see 30 knots top end before the Veems. After the Veems it dropped to 28 knots. But I know cruise 22-23 knots which is a touch faster than before. The boat is a 54 Viking MY on a planing hull. My numbers are from memory. So after all of that I would say the answer to your question is a maybe. Blackdog propellers in Maryland (I think) is the supplier for Veems for Viking and they might be able to help you answer your question. There are other shops and brands as well that may be able to help you.

55 Sea Ray R · Nov 30, 2021

Thanks they are so expensive I really haven''t contemplated it too much. Maybe this spring.

Maxwell · Nov 30, 2021

We switched from 4 Blade Michigan wheels to Veem interceptors in 2020 on our Cat C12 powered Tiara and had a similar experience to what MY lover stated... increased cruise by roughly 3/4kt and gained a little efficiency. At a cost of $11K+, not enough difference to make a change imho, however we changed as we were chasing a little bit of cavitation burn on the original wheels.

Max

55 Sea Ray R · Nov 30, 2021

Maxwell said: ↑

We switched from 4 Blade Michigan wheels to Veem interceptors in 2020 on our Cat C12 powered Tiara and had a similar experience to what MY lover stated... increased cruise by roughly 3/4kt and gained a little efficiency. At a cost of $11K+, not enough difference to make a change imho, however we changed as we were chasing a little bit of cavitation burn on the original wheels.

Max
Click to expand...

Thanks I do a good bit of Running just tokk boat to Wanchese NC form Jupiter FL 3 to 4 would make some difference. Thx

Maxwell · Nov 30, 2021

Just to be clear, it was .75 KT gain not 3-4kt.

55 Sea Ray R · Nov 30, 2021

Maxwell said: ↑

Just to be clear, it was .75 KT gain not 3-4kt.
Click to expand...

Thanks for clearing that up for sure.

motoryachtlover · Nov 30, 2021

Based on what little I know of your situation if you are looking for significant increases in speed I don’t think 5 bladed propellers will get you there. I think you will be disappointed with the results vs. the money you spent. I bought new propellers because my existing ones where getting thin. Any performance gains I achieved were looked at as a bonus.

55 Sea Ray R · Nov 30, 2021

I wish I could rationalize it but I have a spare set as well so I would really have to work a con job on myself.

mapism · Nov 30, 2021

From what you are saying, it sounds like the boat itself ain't a monster of efficiency, and what you get is what she can deliver.
I mean, unless you see a load significantly below 100% by the time you hit the limiter at 2350 - in which case you could try higher pitch wheels, rather than think of changing the number of blades - maybe there's nothing wrong with the boat performance.
Did she ever go faster in the past, and/or are you aware of other similar ones who do?

PS: BTW, your engines must be 3406 surely, not 3408.
Maybe they are susceptible to being called with a wrong name...?
Pretty good stuff anyhow, jokes aside.

55 Sea Ray R · Nov 30, 2021

mapism said: ↑

From what you are saying, it sounds like the boat itself ain't a monster of efficiency, and what you get is what she can deliver.
I mean, unless you see a load significantly below 100% by the time you hit the limiter at 2350 - in which case you could try higher pitch wheels, rather than think of changing the number of blades - maybe there's nothing wrong with the boat performance.
Did she ever go faster in the past, and/or are you aware of other similar ones who do?

PS: BTW, your engines must be 3406 surely, not 3408
Maybe they are susceptible to being called with a wrong name...?
Pretty good stuff anyhow, jokes aside.
Click to expand...

Nope 3408 for sure 8 Cylinder Cat's. Not inline 6's. 2350 RPM's is the limiter, 80% is around 1875. had one guy so adamant they were not 3408's he handed me 50 bucks when he came out of the engine room. Do not know what you are running but 26.5 knots is not exactly crawling in a 55 FT boat you do know the difference between knots and MPH right. I have seen 32 knots WOT.

mapism · Nov 30, 2021

Wow. Weren't the 3408 phased out in the 80s...!?
Ref. what I'm running, by coincidence it's a similar sized flybridge boat (56'), and with exactly the very same power/rpm, only delivered by MAN V8 rather than CAT.
Not sure about the weight of yours, mine is in the 60k lbs ballpark.
2004 vintage (so, not as old as yours, I guess?), but she still can reach 32 kts (loaded) either. Or even 33, when clean and in a good mood.

Back to the point, if you've seen 32 and you're now making 26.5 @ 2350, pretty sure some relevant change must have happened in between.
Very different (and shorter) props would be the more obvious guess, but still a guess, anyway.
But mind, when I mentioned the engine load, I meant the number that you can only get from digital display of electronically controlled engines.
This can show you if the engines, also at full throttle and running at the limiter, can possibly be giving LESS than 100% of their rated power - typically, because a too short prop does not demand all the power that the engine could deliver.
I said that assuming that you had 3406 engines, which can provide this data.
But I can't even remember if also the 3408 already did - probably not, I would think.
Someone with a better memory than mine hopefully will soon confirm...

55 Sea Ray R · Nov 30, 2021

mapism said: ↑

Wow. Weren't the 3408 phased out in the 80s...!?
Ref. what I'm running, by coincidence it's a similar sized flybridge boat (56'), and with exactly the very same power/rpm, only delivered by MAN V8 rather than CAT.
Not sure about the weight of yours, mine is in the 60k lbs ballpark.
2004 vintage (so, not as old as yours, I guess?), but she still can reach 32 kts (loaded) either. Or even 33, when clean and in a good mood.

Back to the point, if you've seen 32 and you're now making 26.5 @ 2350, pretty sure some relevant change must have happened in between.
Very different (and shorter) props would be the more obvious guess, but still a guess, anyway.
But mind, when I mentioned the engine load, I meant the number that you can only get from digital display of electronically controlled engines.
This can show you if the engines, also at full throttle and running at the limiter, can possibly be giving LESS than 100% of their rated power - typically, because a too short prop does not demand all the power that the engine could deliver.
I said that assuming that you had 3406 engines, which can provide this data.
But I can't even remember if also the 3408 already did - probably not, I would think.
Someone with a better memory than mine hopefully will soon confirm...
Click to expand...

Actually 26.5 knots 80% load 1875 RPMS. WOT 2350 32 knots. I will say I have never bothered to look at load when at 2350 but that is a great idea. YOu might be right on the phase out I do know when getting cat parts they have never looked at me and said that it wasn't a 1996. I have a very good source though my son works at cat.

55 Sea Ray R · Nov 30, 2021

mapism said: ↑

Wow. Weren't the 3408 phased out in the 80s...!?
Ref. what I'm running, by coincidence it's a similar sized flybridge boat (56'), and with exactly the very same power/rpm, only delivered by MAN V8 rather than CAT.
Not sure about the weight of yours, mine is in the 60k lbs ballpark.
2004 vintage (so, not as old as yours, I guess?), but she still can reach 32 kts (loaded) either. Or even 33, when clean and in a good mood.

Back to the point, if you've seen 32 and you're now making 26.5 @ 2350, pretty sure some relevant change must have happened in between.
Very different (and shorter) props would be the more obvious guess, but still a guess, anyway.
But mind, when I mentioned the engine load, I meant the number that you can only get from digital display of electronically controlled engines.
This can show you if the engines, also at full throttle and running at the limiter, can possibly be giving LESS than 100% of their rated power - typically, because a too short prop does not demand all the power that the engine could deliver.
I said that assuming that you had 3406 engines, which can provide this data.
But I can't even remember if also the 3408 already did - probably not, I would think.
Someone with a better memory than mine hopefully will soon confirm...
Click to expand...

Looked up per Cat, build year 1996.

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55 Sea Ray with 3408 800 Cat's prop question

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