500/520 DB official thread

[rlynch03]

As I get to know my new 07 52 Sedan bridge I am pretty sure there is very little speed or efficiency gain to using the trim tabs around 2000 RPM’s.

I thought for a minute that I was running slightly faster with +/- 50% tab but couldn’t duplicate it...

What are you guys seeing with yours?

 

[Jeremygavin]

As I get to know my new 07 52 Sedan bridge I am pretty sure there is very little speed or efficiency gain to using the trim tabs around 2000 RPM’s.

I thought for a minute that I was running slightly faster with +/- 50% tab but couldn’t duplicate it...

What are you guys seeing with yours?

I have not noticed any increased efficiency with the use of the tabs. I only use them to level the boat or help me maintain planning at lower speeds. With the straight inboards we have it puts the engines fairly far forward in the hull so they are pretty well balanced in that regard so it makes sense why adding tabs doesn’t gain any efficiency. My friend has a 51 Fly with v-drives and QSM11s and it is amazing how far back his motors are compared to the 52DB. It would make sense that he needs some tabs to help offset the stern weight in that boat.

 

[Havana Shamrock]

My tabs are always at full “down” I never touch them if I take them up my boat slows down

 

[Jeremygavin]

My tabs are always at full “down” I never touch them if I take them up my boat slows down

Interesting, I have the updated cockpit layout and with that comes a long pod that they grafted on the transom. I assumed it was for buoyancy because of the hydraulic platform hanging off the back but Maybe this pod acts like a tab itself to help keep my stern up as I have not noticed a increase in speed with the tabs down. In fact if I run with them all the way down in calm conditions I lose a bit of speed.

Here is a pic of that pod that I took at the survey last year

 

[rlynch03]

My tabs are always at full “down” I never touch them if I take them up my boat slows down

Wow, my boat seams to bow steer a bit with full tab down at cruise speeds... but haven’t ran very much at all with full tab down.

I do like the attitude a bit better with 50%-70% tab down.

 

[Charlesoceanone]

I also have the extension of the hull on the center beam. If I put tabs down I will drop the nose with a slight reduced speed. Operates the same as any other boat I’ve owned with the tabs.

 

[rlynch03]

Would you go with 28 x 30 pitch props in my case or go less in your opinion

Took my props to the tuning shop today. Props are Hy Torq 28"x32". Based on my current numbers they are convinced that 1.5" pitch is enough to get to our goal of 19-20 GPH at 2000 RPM. See below, current numbers. Hope to update everyone this weekend with the results.

Current:
1500rpm - 14.4 GPH - 14.9 mph
1700rpm - 17 GPH - 19.7 mph
1900rpm- 20.9 - GPH - 25.4 mph
2000rpm- 23 - GPH - 29.2 mph
2100rpm - 25 -GPH - 30.5 mph
2300rpm - 31 GPH - 34.6 mph

GOAL:
2000 - 19.0 GPH - 26mph

 

[rlynch03]

Ok, here’s some data which is fresh from a lot of work done.

I had Cummins pull down both QSM11 engines raw water coolers, heat exchangers, replace one Aftercooler as the PO replaced on in December 2016. I didn’t really want to have 12 years difference in age of the Aftercooler.

We follows Cummins newest protcall as of April 2018. Pulled manifolds, heat shields, turbos and replaced both manifolds with new rather than sending out to be shaved flat and then fight to reinstall them. All new studs, new spacers, baskets which are really more like metal shims, turbo heat shields.

One of the first things I should note is the props where 28” 32 pitch when we started. The progression of pitch reduction has taken me to 28.5” and the results are as follows. Fully loaded with fuel, water, gear and personal belonging which includes a full liquor cabinet and Highfiled Ocean Master 390 Aluminum center console, full of furl with 40HP Honda on a Hurley H30+ Davit system.

Headed South to Key West run at this time in very calm seas at 2020 RPMs, Port & Starboard indicating 80% throttle with 64%-65% engine load, 20.8 & 21.4 Boost pressure, 20.4 & 20.1 GPH, EGT showing 975/980 degrees fluctuating and 22nmh+-.

Based on my last 20 months of working on the engines, props and running conditions I’ve come to the conclusion that this is about as good as I’m going to get, I can drop the tender off which all in weighs 725lbs.

The boat runs and planes fine. Obviously the extra tender weight is going to be more weight than most run with but I like having it with us all the time when we’re doing lots of outside running along the coast.

My observation about the EGT is you need to stay under 1,000 degrees and most problems seem temperature wise to be more common when running under 1800RPMs. You try and drop back to 1500-1800 to better match comfort when running in rougher water conditions your temperatures shoots up very quickly. Looks to me like I run much better around 2000RPMs than less.

I’ve made 4 pitch adjustments each time think I was going to see considerable change with the EGT dropping and have not found that to be the case. It almost seems like 950-985 is the normal running EGT range I see. I have no idea what you’d have to do to stay in the <900 degree range other than trawl around of operate in much colder northern waters during the summer time.

I’ve read everything I could fine that Tony has put out but this is what I am seeing and love to see & hear about what others are seeing?

John

PS, someone tell me how to post the pictures of the gauges and I’ll be happy to!

John:
so you ended up taking 3.5" of pitch out of it? My prop guy did not want to take 2" of pitch out of mine. He only want to do 1.5" and i pushed him to that number he wanted to start with 1".

Can anyone else share their numbers?

 

[techmitch]

D CNE below


Took my props to the tuning shop today. They are Hy Torq brand 28"x32". Based on my current numbers they were convinced that 1.5" is enough cup to remove at this time. See below current numbers. Hope to update everyone this weekend with the results.

Current:
1500rpm - 14.4 GPH - 14.9 mph
1700rpm - 17 GPH - 19.7 mph
1900rpm- 20.9 - GPH - 25.4 mph
2000rpm- 23 - GPH - 29.2 mph
2100rpm - 25 -GPH - 30.5 mph
2300rpm - 31 GPH - 34.6 mph

GOAL:
2000 - 19.0 GPH - 26mph

John:
so you ended up taking 3.5" of pitch out of it? My prop guy did not want to take 2" of pitch out of mine. He only want to do 1.5" and i pushed him to that number he wanted to start with 1".

Can anyone else share their numbers?

Pitch and cup are 2 completely different things. Just trying to learn.

 

[cod]

Wow, my boat seams to bow steer a bit with full tab down at cruise speeds... but haven’t ran very much at all with full tab down.

I do like the attitude a bit better with 50%-70% tab down.

+1. In addition, I would say I pick up 1 kt. with setting the tabs at 50-70%.

 

[rlynch03]

I will be at

I will be interested to see your new numbers. I’m assuming you mean pitch not cup correct?

Sorry, Yes pitch...not Cup

 

[Jeremygavin]

D CNE below


Took my props to the tuning shop today. Props are Hy Torq 28"x32". Based on my current numbers they are convinced that 1.5" pitch is enough to get to our goal of 19-20 GPH at 2000 RPM. See below, current numbers. Hope to update everyone this weekend with the results.

Current:
1500rpm - 14.4 GPH - 14.9 mph
1700rpm - 17 GPH - 19.7 mph
1900rpm- 20.9 - GPH - 25.4 mph
2000rpm- 23 - GPH - 29.2 mph
2100rpm - 25 -GPH - 30.5 mph
2300rpm - 31 GPH - 34.6 mph

GOAL:
2000 - 19.0 GPH - 26mph

I will be interested to see your results as well. Your goal at 2000rpms seem a bit optimistic for GPH and MPH but you hate to take out too much pitch at once and lose too much cruise speed but I hope you achieve it. Let us know how you
Make out.

 

[quality time]

Cup can also be played with to make smaller incremental changes later. I think you're on the right track with 1.5" pitch and might still hit that speed since you'll be able to cruise at a higher RPM now. I didn't lose any speed after dropping 1" pitch and multiple cups.

 

[rlynch03]

D CNE below


Took my props to the tuning shop today. Props are Hy Torq 28"x32". Based on my current numbers they are convinced that 1.5" pitch is enough to get to our goal of 19-20 GPH at 2000 RPM. See below, current numbers. Hope to update everyone this weekend with the results.

Current:
1500rpm - 14.4 GPH - 14.9 mph
1700rpm - 17 GPH - 19.7 mph
1900rpm- 20.9 - GPH - 25.4 mph
2000rpm- 23 - GPH - 29.2 mph
2100rpm - 25 -GPH - 30.5 mph
2300rpm - 31 GPH - 34.6 mph

GOAL:
2000 - 19.0 GPH - 26mph

Props are back from the tuner. Should be back on the boat tomorrow and Friday I will go for a test run.

 

[rlynch03]

Having the props tuned next week.

Cu

Took my props to the tuning shop today. Props are Hy Torq 28"x32". Based on my current numbers they are convinced that 1.5" pitch is enough to get to our goal of 19-20 GPH at 2000 RPM. See below, current numbers. Hope to update everyone this weekend with the results.

Current:
1500rpm - 14.4 GPH - 14.9 mph
1700rpm - 17 GPH - 19.7 mph
1900rpm- 20.9 - GPH - 25.4 mph
2000rpm- 23 - GPH - 29.2 mph
2100rpm - 25 -GPH - 30.5 mph
2300rpm - 31 GPH - 34.6 mph

GOAL:
2000 - 19.0 GPH - 26mph

Pretty close to the goal. Thanks to Black Dog Propellers, took 1.5” of pitch out.

Pitch went from 32.300 to 30.795

I didn’t document all the ranges but with with a little over a half tank of fuel and half tank of water and 75% TABS, 2000rpm - 19.8gph - 26.8mph

Load went from 74-78% Load at 2000rpm to 64-68% load

Also noted with ZERO TAB I was at 2000rpm, 20.3GPH and 26.0mph

Pretty happy with that. Not sure I need to take any more off...

 

[Jeremygavin]

Having the props tuned next week.

Cu


Pretty close to the goal. Thanks to Black Dog Propellers, took 1.5” of pitch out.

Pitch went from 32.300 to 30.795

I didn’t document all the ranges but with with a little over a half tank of fuel and half tank of water at 2000rpm - 19.8gph - 26.8mph

Pretty happy with that. Not sure I need to take any more off...

Those numbers seem great to me. I would be happy with that. I have about the same pitch in my props and I am running a little higher than that for GPH and a little less on speed. Do you know what the props have for cup in them?

 

[rlynch03]

Not sure exactly on the cup but Gene did say I have some and we could adjust that for small gains

Did you notice that I am picking up a little speed 1mph and almost 1gph by trimming down 75%?

 

[Gimme Time]

Having the props tuned next week.

Cu


Pretty close to the goal. Thanks to Black Dog Propellers, took 1.5” of pitch out.

Pitch went from 32.300 to 30.795

I didn’t document all the ranges but with with a little over a half tank of fuel and half tank of water and 75% TABS, 2000rpm - 19.8gph - 26.8mph

Also noted with ZERO TAB I was at 2000rpm, 20.3GPH and 26.0mph

Pretty happy with that. Not sure I need to take any more off...

Do you know what your EGTs are at 1700, 1800, 1900, 2000 RPMs which is where most all QSM-11s with 660 or 715 HP are? That’s were the rubber hits the road when EGTs climb well above 1,000 degrees, the dry exhaust gas manifolds start cooking, expansion and EG leaks start flowing from what I’ve read? With out EGT analog or preferable digital gauges you’ve got no way to know where you heat temps are hitting. The Cummins digital engine info only gives you water temps not EGT info!

BlackDog did all my prop tuning and I’m running no cupping, pitch is 28.5” now.

 

[rlynch03]

Don’t have a EGT monitor. Also I just updated the post. I was at 74-78% load at 2000rpm’s now I am at 64-68% load at 2000rpm

 

[Jeremygavin]

Not sure exactly on the cup but Gene did say I have some and we could adjust that for small gains

Did you notice that I am picking up a little speed 1mph and almost 1gph by trimming down 75%?

Yes, after you and a few others have said they run with trim I tried trimming again this weekend and it actually slows me down just a little bit.