Getting her to plane cleaning again?

[stormchaser]

OK, so, due to weight of all of our live abaord stuff (that is not going away)...Saraswati won't plane cleanly. At WOT she is still not fully on plane. She used to top out at 17.9 and now tops out at about 15.8. I'd like to try to get her back up on plane. So, there's my plane, please give comments and suggestions...and let me know whether you think it might work or if there is anything else I should try.

1. Props: She is over propped by 150-200 rpm. Going to pull the wheels and send them to Black Dog to have the pitch redone and to have them tuned to the highest degree possible. I was thinking take out 1.5" of pitch, but maybe 1" is a better choice?

2. Trim tabs: I feel like the tabs are under sized and/or don't extend low enough to push the bow down properly. When hauled, I was thinking of putting extension blocks at the bottom of the tab hydraulic rams...that way they will extend down about inch or two. I knot this means that my tabs will always be "bow down" a bit even when full retracted and that might make handing in stern seas a bit wonky, but I don't really go out in bad conditions, I'm a fair weather boater and full time live aboard.

3. Not keep her tanks full. Is there any disadvantage to only keeping her fuel tanks about 1/2 full and just fueling up a bit more often?

Any other suggestions other than reducing weight?

 

[garyd]

Now you know how the nation feels under Obutthead. The U.S.A. just can't get back on top.

Well you could try spending your way out of it. Throw money at it say 150-200k So it will plane again.

You could lighten the load but since your a Democrate why not tax everyone in your marina because your boat won't plane it must be their fault. LOL

Now seriously, make sure the bottom is clean. Make sure the props are clean. 1/4 -1/2 fuel, 1/4 water or less, no waste water.


Then take all your stuff and set it out on the dock go for a ride. Have a garage sale then only put back on the stuff you have actually used over the last 12 months. Take everything else home unless it is very light.

garyd

 

[TopHattandTails]

I think I have this right - but logic tells me that if she's over propped (typical with age and weight), then by detuning them a bit will allow the motors to load correctly (a good thing). However, that will also decrease your speed at the same RPM (or more importantly allow you to increase your RPM to the correct load speed and get back most of the speed that you lost, but definitely not gain speed). If you plan on running at the same RPM as prior (WOT) and your actually getting 2350 RPM at WOT before and after tune, then your speed will decrease, thus adding to your planing problem with a slower speed. This assumes that you are getting 2350 at WOT with overloaded props now, and that you will also get to 2350 at WOT with tuned props. So by detuning the pitch of the prop to allow accurate loading you will not be helping the speed for planing purposes. Just a comparison question - your speeds are reported in MPH or knots? I tuned our props with instructions to allow a 2350 WOT to allow for full fuel tanks high temps with high humidity. Took 3.5 degrees out via Propscan.

Trim tabs - great idea. Rather than blocking them I would extend them (with extra lateral support to prevent folding. That will allow full bow up and allow you to push the bow down further than OEM. This is on the list for us.

Tanks - I agree with that idea. Allows you to keep some weight off, but more importantly, allows you to turn over the fuel more often and ensure fresh fuel in the tanks. If your going to burn a 10 hour burn, then fill 'em up. But for 1-3 hour joy rides, let 'em be a little low. You might turn up some dirt the first few hours / fill ups - but that's never a bad thing to remove. Just have extra filters on hand and a few pony bottles for re-priming.

Not sure I've ever had our 53MY on plane. I joke that you could drop us from the moon and we might hit 15 knots! We typically cruise at 13 knots with 1900 - 1925 RPM's and WOT at 2200 - 2300 RPM gets us up to 14.5 knots after a quarter mile or so. Not a lot of weight on board other than weekend supplies. The joy is in the passage!

 

[1Hogtow]

Garyd,
Great Analogy
Put it in every boating paper you know of.
Brad

 

[stormchaser]

Terrible analogy, Obama has done much good to our reputation in the internatinal arena, we are no longer hated and a laughing stock like we were under Bush. But please, lets not turn this into a political dicussion. Thanks.

As far as RPM goes, like I said, I cannot get to 2350 right now. Depending on which tachs you believe, I'm at 2150-2200 at WOT. That's why I'm hoping that I can regain some speed with prop work. I believe (correct me if I'm wrong), but if I can't get to 2350, that means I'm not really getting the full 425/435hp and I need every pony I can. Also having a more efficient prop will help get more of the power changed into propulsion and less into slip.

 

[labrador]

Dave, WHAT PLANET DO YOU LIVE ON???????????

 

[stormchaser]

I believe you would call it planet Libtard. hahaha, but lets keep it on track...ummm...kayyyy?

 

[REBrueckner]

Impossible to provide specific input because you do not state your objective, nor enough background to asess why you lost 2 knots of top end speed, nor what engines and HP you have. I assume you have 8V71TI's with N90 injectors? Any work done on those engines during the period when RPM declined??

Tophatts first paragraph is incomprehensible to me.

I really wonder what "essentials" you added that would slow you down two knots....that's a LOT!!....are you SURE there are not other factors? If both engines used to run at 2350 WOT and are now down 150 or 200 RPM have you checked for things like full movement of throttles, governor settings, no load RPM, etc,etc,etc.

There is certainly nothing to lose by getting your props tuned except the cost of that tuning. During haulout, before prop removal, I suggest you whack each prop with a hard rubber mallet or a piece of wood to be sure each "rings" true...indicating good solid material......if not, don't spend money getting the old prop precisely tuned...get a new prop and tune that...

Instead of readjusting trim tabs, why not just add a "wedge" either side of the tabs where you have room...that's a fixed, non moving change that will not disturb your trim tabs....you can also thicken such wedges later and add wedges to the tabs later if you find you need more "bow down".

The only real disadvantage of half empty tanks is condensation during rapid changes in temperature during cold weather...if your boat remains heated that should not be a problem. But at perhaps ten knots normal cruise, the extra weight is likely insignificant regarding speed.

I removed my spare stub shafts as my trim was off and stored them at home ....I figured the chances of my using them while away was negligible...maybe you could take spare props off too?? Or move stubs and props forward to aid trim. If your water tank is forward, keeping it rather full aids trim but likely not speed.

 

[Pascal]

start with weight and clean bottom / running gear. it only takes a few barnacles, esp. on the props, to loose a knot. it's huge.

weight, dont' fill up and try playing with weight distribution. esp. water.. if you have 1000lbs of water near the stern, that's a lot. try running without the tender to see what that does (another 700lbs aft). and maybe, put more fuel in the fwd tank to get more lift aft.

even on a good day, the 53 will strugle to stay on plane without pushing the engines.

do the above before wasting money on prop work.

do those tests in neutral conditons (wind/tide) and get the tachs checked to know what you really get.

 

[MikeP]

Totally agree w/Pascal - don't spend a dime on propwork until everything else is checked/cleaned/whatever. Our top speed/Rpm dropped from 17.6K and 2200RPM to 10.5K and 1800 RPM due to barnacles on the shaft/prop. Dove boat, cleaned shafts/prop, speed and RPM back up to normal. Don't over-science this stuff.

 

[stormchaser]

Goal is to be able to plane again, if possible. I've checked pretty much everything. Engines rev fine in neutral_ bottom is spotless, engines are 871TI at 425/435hp and maintain 180f at WOT The loss of speed happened as soon as we moved all of our live aboard. We added a lot of heavy stuff. Wife has every closet packed, dozens of pairs of shoes, dozens of pairs of boots, motorrcycle stuff, a heavy cast iron firepit on the aft deck, a heavt dining table where the dinette used to be, reclining couches, 42" plasma in a very heavy lift cabinet in the salon, 36" plasma in the master, full sized polk audio tower speakers in the salon, full sized stainless Weber grill on the flybridge, oversized Fisher Paykel fridge, every kitchen gadget you can imagine, full water and full fuel, and the list just goes on...we have added many many tons of weight.

 

[SeaEric]

Good grief, you've got a lot of heavy junk onboard. Cast iron fire pit?? eeek.

Let Black Dog tell you what mods to make on the props. Their tweaks got me another knot at cruise on my 46 Matthews. They are pricey, but I think it was money well spent.

 

[stormchaser]

Yes, a cast iron and tile fire pit. She's our home and we've set her up to have all the creature comforts of a real home. I realize that may very well mean never really planing again, but I at least want to do what I can. Oh, forgot to mention that there is also a whaler up top and one anchor with all chain rhode and a secondard anchor w 25ft of chain and 200ft of line. So yeah_ she is very heavy. She sits a good 2" lower than when we got her.

 

[REBrueckner]

That description helps....I now doubt tab changes or wedges will make any difference due to all that extra weight, unless it's concentrated aft.

Have your props calibrated and an inch or so of pitch removed to reach 2300 RPM. My 1978 8V71TI DD spec sheet shows WOT is 2300 RPM which was also the rated RPM on my own 1972 8V71TI's.

But I'd not expect more than maybe a 2% change in prop efficiency unless you have some current vibration...5% would be a very pleasant surprise....(just guesses).

My spec sheet prop load curve shows a 25HP increase for each 100 RPM increase at around 2100 to 2300 RPM...but I don't know if all that will be reflected in a reduction in pitch ....but as noted, to the degree an increase in prop efficiency is achieved THAT should clearly help.
good luck

 

[stormchaser]

indeed, a lot of the weight IS aft...firepit, grill, full water tanks, clothes/shoes/boots. All storage in the master is packed and we even added a chest of drawers and those are full too. Also she has a LOT of heavy mirrors on the master. I want to remove them but it will be a major undertaking, they are GLUED obto the original wood. Anyone got a set of spare closet doors they wanna get rid of?

 

[stormchaser]

Oh_ she acts like she is going to fully plane off and the bow does start to come down but she just stays a bit bow high...partailly planed off.

 

[Nonchalant1]

Yes, a cast iron and tile fire pit. She's our home and we've set her up to have all the creature comforts of a real home. I realize that may very well mean never really planing again, but I at least want to do what I can. Oh, forgot to mention that there is also a whaler up top and one anchor with all chain rhode and a secondard anchor w 25ft of chain and 200ft of line. So yeah_ she is very heavy. She sits a good 2" lower than when we got her.

Cast iron fire pit on the aft deck? Where does the smoke go? There's a white fiberglass ceiling on your aft deck, right?

 

[stormchaser]

We use clean burning jelled alcohol as the fuel. No smoke and puts out enough heat that w 2-3 can going at once, we comfortbly had Christmas Dinner on the aft deck last year and ouside temps were in the upper 30s.

 

[DLCameron2]

Stormy:

Please be careful about CO poisoning with that fire pit. You should get a meter and put it nearby just to be safe!

DC

 

[SKYCHENEY]

I agree with first cleaning bottom and props. Next get a photo tach and check your no load WOT RPM and your loaded WOT RPM. This will tell you if you are really overloaded or if you have other issues. You may just need a tune up on those engines. Have you changed fuel filters recently? Maybe you're not getting enough fuel to make full RPM. Just some things to check before messing with props.