Wot numbers

[jonathanschanter]

So after my fuse mishap I finally got my wot numbers. Half fuel half water and an empty boat. (Light load). Wot with sync on port 2620 28psi boost 1000egt. Star 2660 28psi 1000egt
Sync off port 2638 star 2660 same boost and egt.
Rpm per etna digital guages and psi egt per turbocator by sbmar. Pulling props to have recomed what should I do. 5 blade nibral props.
Why am I not getting full wot with sync on?
Side question how do I add photos?

Topic

[Tony Athens]

A tad off topic, but if you prop to what you want in fresh water, when you move to salt water, you could easly pick up 5% in vessel speed at the same engine RPM or see a 5% reduction in engine load/GPH at the same vessel speed. .

[Steve Lewis]

Tim,

We have the hard top and factory hydraulic lift as well but we do not have a tender/dinghy. We use an inflatable paddle board. I will ask the yard to tell us what the strain gauge indicates on the travel lift when we launch in the Spring. Granted we are at 7/8 fuel, little to no water or waste and none of our stuff. We usually run with half a tank of fuel, 1/3 tank of water and 1/2 or less in the waste tank. All of our stuff adds ~1/2ton but we would be close on weight in the sling after everything settles out into our normal trim.

Right now we are running 23×26 props and at ~2140 we are running 22mph+ and burning 28-29gph. Since our prop slip is in the 22-25% range I am hoping that when we take the other inch out that will lift the 28-29gph burn north of 2220. So our 22mph speed will move from 2140 up the range to some where at or over 2200. The goal is to maintain speed and fuel burn values but move those up the rpm range to 2230 or a little more than that. We will have the new heads so I figure this will give us good longevity until we decide to get something else. As fuel burns off we see our speed pick up to 23mph and the fuel burn reduces to 27gph when running 2140. I even saw 26 gph once. Tail wind and wave I bet…….. We will also have the Pyros next season so we can add that to the mix of how we run long legs of our trips.

We are in the western basin of Lake Erie and next year we will do our summer trip to Buffalo, NY. That is a well known cruising route for us and we have convenient access to Towboat at every port city along the route. We are always within 25miles of a Towboat installation. Seems prudent to cruise this kind of trip the first season after major head work “Just in case”. The following season we will head back north into Lakes Huron and Michigan.

What is your vessel speed at 2200rpm? I know our conditions are different but I am curious how yours runs.

Happy Holidays!

[Tim]

23×25

I too have the 480ce’s but my 460 dancer , I think, is a lot heavier than yours (hardtop + hydraulic platform). Last time out we weighed her full fuel, full water, lots of alcohol + dinghy on back and right at 40k. Anyway, I run the 23×25 props and @2200rpm I’m right around 13.6gph each engine. However, my speed suffered for sure and dropped 2-3mph. Just a heads up so you aren’t expecting to run at the same mph. Hope this helps you!

[jonathanschanter]

Wow

Wow thank you very much! Thank you for taking the time to be so thorough. Comes spring I will let you know how I make out!

[Steve Lewis]

I plugged the numbers that you posted on October 16th into my spreadsheet and entered your trans and pitch numbers. Your prop slip appears to be quite good for that run. Prop slip values range from 23% at its worst down to 17% at its best. You indicated that you cruise in the 2250 range so the slip value that I calculated is ~18.5%.

My conclusion is that since you recorded these numbers with half a load AND your slip numbers look pretty good at this point you might look at taking 1 inch out now and see what that does to your EGT values and see if that gets your WOT number closer to 2730. Spend a season collecting numbers at your cruise rpm each time you go out and enter them in your log book. Then you can make a determination about taking another inch out next time you haul the boat.

I have the 480ce’s so my smartcrap display is a very easy way for me to spot check fuel burn, speed, rpm and engine temp. I do not record the values every time but spot check the values against my known full load base line. I am taking another inch out now that she is up on the hard.

Your numbers indicate that your vessel speed is 28mph @ 2270 so you might see a minor decrease in that speed but nothing that would be objectionable in my book. Every one is different though…….

I attached my spreadsheet that has the formula in it for calculating prop slip. Your data is the bottom block. You can use the spreadsheet by cleaning it up and removing my stuff from the top and keeping a running log of your numbers at various points in the season. Ignore the gph and mpg columns as I assume you have no measure for fuel burn. Floscans or maretron are options if you want that. But you can add columns for Boost and EGT so that you have them for comparison and can easily see how the pitch modifications change your values.

Anyone that wants to use this spreadsheet needs to change 3 values. RPM values should be pretty self explanatory but the prop pitch and trans ratio values are the important ones. Cell A48 is pitch and column I is the ratio. You will see it there and you can see it referenced in the formula. This all assumes that you are proficient with Excel Spreadsheets and reading those formulas.

You asked a question about the difference in WOT numbers while sync is on or off. My read of that is your Port engine is the Master and Starboard is the slave. There are mechanical linkages involved so I bet that a few things need adjustment for it to work perfectly throughout the full rpm range. However Tony is right. Since we should not be running at WOT for our normal cruising needs, the fact that it works properly in your cruise range means you can leave it alone. “If it aint broke, don’t fix it”

This will be a long 6 month off season for us here in Ohio. We have a lot of Big Work being done on the boat. I fully expect that we will be nicely dialed in and ready for serious cruising for 2022.

1 user thanked author for this post.

Tony Athens

[jonathanschanter]

Numbers

Picture didn’t go through. The gear box is zf with a 1.500 ratio. Props are 22×24 5 blade nibral

[jonathanschanter]

Got numbers

So I finally got my prop size and gear box numbers. What do you guys think I should dop

[jonathanschanter]

Understood. I’ll get the ratios one day this week but the the current prop specs are going to have to wait till I haul. Probably over the next week or two. So I’ll put this conversation on hold till I haul. Thanks again for your time!

[Steve Lewis]

Jonathan,

Since you have Mechanical 6CTA’s ideally you want 105% of 2600 which is 2730ish @wot…..

What is your transmission ratio and current propeller pitch? The reason I ask is that I took an inch out of my props at the beginning of the season and it did not have the desired effect. I was looking to reduce fuel burn at 2200rpm to get it at/under the Diamond 450 curve and ended up reducing prop slip so my same fuel burn @2200 went down the rpm range to 2140 instead of going up the rpm range to 2300. WOT= 2680 before I did the prop work AND after I did the prop work. I have 480CE’s so the governor is doing its job.

Prop slip went from ~32% to ~26% by reducing pitch by 1 inch. I am going to take another inch out now that we are hauled out and put away for the winter. By knowing your trans ratio and prop pitch we can compare theoretical speed at your recorded rpm values to the actual speed as you have recorded them in the posted chart. We can then see what your slip value is and if 1 inch is going to be appropriate or maybe you would be looking at more……..

Not to mention that you might get your EGT values down a bit.

My prop specs:
Props were 23×27 April 2021 when we bought the boat
Props now 23×26 July 2021after we got the work done
Prop goal 23×25 Winter 2021/2022

Lesson learned = there is more to it than “Just taking an inch out”

[jonathanschanter]

No matter what my weight I always run at 2250-2270. So you say I’m asking for everything my motors have to give. How do I lighten up there load? I’m sending the props out this winter. What should I ask them to do? I think one pitch would be to much. I only want another what 60-100rpm?

[Tony Athens]

You are asking 100% of every thing your engine have to give ( and maybe more) and you are not even full up……………With that said, where do you cruise at as to RPM at this weight?? What about when you are “full-up?

As to your sync thing–Who knows, but that should not matter unless you cruise at WOT ( I certainly hope not)..?

[jonathanschanter]

Sorry dropped the ball on that part. There 6cta 8.3 450 diamonds. I just figured out how to add photos. The last three numbers are as followed. Sync on then sync off then turned from an east direction to a north direction

[Tony Athens]

What exact engine???

[Author]

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