Prop help

Blown284

Well-Known Member
Jan 12, 2014
1,117
Chesapeake Bay
Boat Info
2004 SeaRay Sundancer 460
Engines
Cummings 480CE
Hi everyone. I switched from 23 x 27 props last season due to being severely overpropped (according to fuel curves and reading lots of articles on the infamous cummins 480ce engines that I have).

So I moved from the 23x27 prop to 23x25 props and now my fuel burn is spot on at 13.6gph per engine @ 2200 which is exactly where I need to be.

However, here's my issue. The boat is like 2-3mph slower at 2200rpm than it used to be. yes, I know --- serious issue LOL.

I'm asking you, the prop wizards... is there anything I can do to gain some mph back at 2200 besides going back to larger pitch prop? If so,what do you recommend?

Thanks!
 
What is your speed at 2200? What is your wot rpm without the sync on?

you can lighten the boat is probably the only real answer here. Do you know how much your boat weighs from a travelift?
 
speed at 2200 now is 18.3mph - previously 20-21mph (depending on current, wind, etc).

According ot the lift (not sure if it’s accurate or not), the boat was right around 40k.
 
I think that’s pretty much on par with us who have hardtops. I find that running the boat at 2250 really makes the boat happier. What is the wot rpm?
 
Honestly, I can’t remember but I’m within spec of everything I’ve read on these engines. I guess I thought everyone with the hardtops, hydraulic platforms was a few mph more than I. Guess not. Like I said, I’m seeing right around 13.6gph on each engine which is exactly where she needs to be.
 
I have the same boat as you and I will say getting them propped to exactly hit 2650 is the key. I set mine up for 2700 wide open and it cost me a couple knots. Also, against, the norm but 2250-2275 my boat is much happier so I run there. Lastly, make sure you physically check the prop rpm and do not rely on the gauges as the are often inaccurate.
 
I have the same boat as you and I will say getting them propped to exactly hit 2650 is the key. I set mine up for 2700 wide open and it cost me a couple knots. Also, against, the norm but 2250-2275 my boat is much happier so I run there. Lastly, make sure you physically check the prop rpm and do not rely on the gauges as the are often inaccurate.

Great point(s). I noticed a significant difference from 2200 up to 2250 in speed. The boat is winterized (very sad!) but I would be able to hit 2700 wide open the way she’s propped. I just wasn’t expecting to lose 2-3mph. But when running her, she sounded much smoother than with being overpropped that’s for sure. But I agree, 2250 seems to be their “happy place” and I’m more around 20mph sometimes a little more depending on conditions.
 
Sounds like you’re pretty close. We just have slow boats. I dream about having qsc 600’s but hey 430 is what we have and I love mechanical engines.
 
depends on transom setup but I'm in the process of adding a second set of tabs above the tunnels on our 410. Others have reported with the increased lift they get a flatter running angle and pick up 1-2mph. Might be a possibility for the 460 if the boat could run a little flatter, but if it already has the proper tab/trim/running angle it might not help
 
Sounds like you’re pretty close. We just have slow boats. I dream about having qsc 600’s but hey 430 is what we have and I love mechanical engines.

I hear ya. I have the 480CE’s not the 6CTA’s but they have been pretty amazing thus far and I’m not complaining. I propped them just like Tony suggests inline with the 6CTA. My buddy has 51 Sundancer with the QSC 660’s (I think that’s it) and runs around 23-25 mph cruising. I’m jealous.
 
depends on transom setup but I'm in the process of adding a second set of tabs above the tunnels on our 410. Others have reported with the increased lift they get a flatter running angle and pick up 1-2mph. Might be a possibility for the 460 if the boat could run a little flatter, but if it already has the proper tab/trim/running angle it might not help

Yea the 460 requires a LOT of tab and even then, I’ve noticed the bow still runs high. I’ve attached a picture that a friend took this season.
123_1.JPG
 
Yea the 460 requires a LOT of tab and even then, I’ve noticed the bow still runs high. I’ve attached a picture that a friend took this season.View attachment 116059

ours is similar at the lower rpm/speed range. One of the guys on FB with a 410 did this tab upgrade and even the wake looks completely different (flatter)

I'm excited to get them on for next year, its a relatively simple and cheap upgrade as it uses the same pump. The 410 has a nice 14" flat spot above the prop tunnel making it a perfect spot to mount a 12x12
 
on my 450 I rarely use my tabs. it goes up on plane pretty quickly. I did the Tab thing on my older 390 and it made a world of difference. was always thinking of doing it to the 450
 
on my 450 I rarely use my tabs. it goes up on plane pretty quickly. I did the Tab thing on my older 390 and it made a world of difference. was always thinking of doing it to the 450

Ours gets up on plane quick too but it digs a pretty good hole at the stern and With the tabs fully down exhaust temperature rises by about 50°. I’m hoping the extra
Surface area lets me keep the tabs retracted more and should keep egt down
 
I have the same boat as you and I will say getting them propped to exactly hit 2650 is the key. I set mine up for 2700 wide open and it cost me a couple knots. Also, against, the norm but 2250-2275 my boat is much happier so I run there. Lastly, make sure you physically check the prop rpm and do not rely on the gauges as the are often inaccurate.
I play with two sets of props at 25 and 25.5" pitches. They are cupped slightly different. The boat seems happier at 2250 rpm (Aetna gauges) and the WOT is around 2670-2680 or so. Performance increases depending on fuel load from 18 to 20+ knots as we burn diesel. Weight was 35,500 two years ago but I doubt the accuracy of the scale on our travel lift.
 
I play with two sets of props at 25 and 25.5" pitches. They are cupped slightly different. The boat seems happier at 2250 rpm (Aetna gauges) and the WOT is around 2670-2680 or so. Performance increases depending on fuel load from 18 to 20+ knots as we burn diesel. Weight was 35,500 two years ago but I doubt the accuracy of the scale on our travel lift.

We are likely in/around the same weight. Last time I was there I was completely loaded with liquor, full tank of waste (don't ask!), full water, full fuel and they told me I was right around 40k. My boat has hard top and GHS Hydraulic platform. I bet with the 25.5props you gain 1-2mph vs. the 25?
 
We are likely in/around the same weight. Last time I was there I was completely loaded with liquor, full tank of waste (don't ask!), full water, full fuel and they told me I was right around 40k. My boat has hard top and GHS Hydraulic platform. I bet with the 25.5props you gain 1-2mph vs. the 25?
Maybe but it might be in the cupping of the blades. I know our boats are similarly equipped (hardtop, GHS, 600 lb dinghy) but I've put it on a weight loss program by just getting rid of some useless "stuff". I think it helps.
 
Maybe but it might be in the cupping of the blades. I know our boats are similarly equipped (hardtop, GHS, 600 lb dinghy) but I've put it on a weight loss program by just getting rid of some useless "stuff". I think it helps.

I think your dinghy is a lot heavier than mine (no pun intended LOL). I have the lightweight aluminum dinghy and the dinghy and the engine can't be more than 300 lbs tops. It's the highfield 9 foot lightweight model and I have 4 stroke Tohatsu.

I think I'm going to see if black dog props here in Maryland can help me out --- I think you're right that the cupping of the blades is likely different.
 
Has anyone here replaced your manual trim tabs with the Bennett system like this one: https://www.hodgesmarine.com/benap0...5jgYkyyo9DuZYm8ZBsv_MRI7o1-cCzLhoCz70QAvD_BwE

If so, are you happy with this system?

I looked at adding one, but I think you need sensors in the hydraulic rams, so you also have to factor in pulling the boat.

Two guys on my dock have added the Mente Marine system and really like it. It's plug and play with Bennett wiring and you teach it the up/down tab position so no pulling the boat.

Pretty cool system.

http://www.mente-marine.com/
 

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