Trying to find the Proper propping

[Russell Burris]

I have a 2007 460 Cruiser Yacht with D6 Volvo engines. After talking to my friend about Tony’s article on proper propping you boat and reading it I have now know that my boat has never had the proper props on it. My boat was test weight was about 30k pounds when new. I would guess its weight is about 31k now. I have 23x31x2 props on it. The top end RPM’s about 3550 to 3600. My bottom was dirty and I was getting 3150 rpms top end, and it takes 3000 rpms to get on plane. I have now cleaned the bottom and getting about 3300 rpms. I’m topping off the boat with fuel to see what I get with full fuel this week. I have now about 900 hours on the engines, and wondering what kind of damage I might have done? I also, know I don’t have enough trim tabs on the boat. Hard to get the nose down. Maybe Tony will write something on this also?

So, if anyone can help to find the proper props to put on my boat I would appreciate it.

Russ

Topic

[Steve Lewis]

Ideal Conditions

Russ,

Stay with me on this as I am about to hold forth on quite a few ideas but they all converge on what you are going for….. Ideal conditions for operating your boat long term within operating specifications. As Tony points out, and has written about extensively, proper loading of the propellers is the ultimate goal. Believe what he has written back to you! That also means looking at a series of operational conditions. In no particular order……

Hull condition. Keep all wetted surfaces and running gear as clean as possible through the season. I boat in Lake Erie(Ohio) out of a marina that shares its basin with a nature preserve. LOTS of organic matter in the water and very warm. I have our boat, a 2006 Searay 40 Sundancer, hauled mid season to pressure wash the bottom, props, rudders and tabs. This is after I have pressure washed at the beginning of the season before we apply bottom paint AND wash at the end of the season. My goal next year is to have the bottom paint removed, let the hull dry out and then apply 3+ layers of epoxy barrier coat then apply a nice slick bottom paint over the epoxy. Yes it is expensive to do this but cheaper than ruining engines and causing a rebuild by a country mile. This will go a LONG WAY to keeping the boat weight constant throughout the season from a water absorption perspective. You have a LOT of hull in the water to absorb water just like I do. Have your boat hauled out and then ask the lift operator to tell you what the strain gauges indicates for weight at the beginning of the season, at mid season haul out/wash and at winter haul out. Boats Get Heavier! I have observed my fuel burn rates increase as the season progresses. My 8.1L Merc Horizons burn 35GPH at 3500RPM @23mph at the beginning of the season fully loaded and at the end of the season they are burning 42GPH at 3500RPM @ 21MPH similar load. Hope to fix the “Boats get heavier” issue with the barrier coat. Next is your propellers.

The correct propellers are key. Make sure that you are able to stay BELOW the fuel burn curve published by Volvo. This means AT CRUISE. WOT is almost useless, as a prudent boater will not run his/her boat at WOT for any appreciable amount of time. As Tony has written, the greatest amount of damage happens at CRUISE RPM’s because that is where we operate our boats. So make sure you find a propeller pitch that allows your engines to operate BELOW the fuel burn curve at Your Preferred Cruise RPM range. Read and believe Tony’s response to you about removing propeller pitch. WOT will take care of itself if you have the pitch correct at Cruise.

Don’t forget the Exhaust. This one eluded me for quite sometime but now I get it. Having the proper exhaust setup will help the long life of your Turbo. Dry elbows out of the turbo, Riser to gain height above water line then an elbow to start the down draft and THEN a mixer. All with proper physical supports. I have seen too may pictures of engines with wet elbows attached directly to the exhaust side of the turbo or mixers blowing up instead of down. Tony has written about how the water will eventually corrode the fittings and then it is only a matter of time before your turbo is done.

PROPER MAINTENANCE! Not recommended minimums. Aftercoolers, Turbos, Heat Exchangers and water pumps etc require regular care. Ignore what is in the manual and acquaint yourself with the “Seaboard Way”. An ounce or three of prevention will save you Thousands of dollars and heart ache down the sea way.

I have read, re-read and re-read again lots of what Tony and the team have written and come to the conclusion that most boats come from the factory OVER PROPPED. Now the trick is to find a boat, or setup the one you have, to Tony’s time tested specifications and then operate the boat like a yachtsman that cares for his boat like it is his First Mate! It takes time, effort, patience and an eye for detail. Ask questions, challenge the answers and eventually you will get your existing boat setup correctly or find a boat that has been treated well enough and you can fix the things that need fixing so that it will last longer than you.

My ultimate goal is to find a boat that will transport me, my wife, my life long friend and his wife around the Great Loop as many times as we can in comfort, safety and with reliability. I have a few years to find that boat and get it setup properly. Hopefully you can get yours setup the same and enjoy countless worry free hours. Until then we will enjoy and setup the one we have!

Steve Lewis
Aquaholic
2006 Searay 40 Sundancer
“Dreaming of Diesels”

1 user thanked author for this post.

Tony Athens

[Tony Athens]

Over Propped D-6's

Your engines are no different than any engine in this class as to being loaded properly.. You have 5.5 liters, and from the vintage of them, I’d guess 370HP at a minimum rated 3500 RPM. Close?

That is right in there with a QSB 5.9 rated at 380 MHP at 3000 RPM from those years.. So let’s use my thoughts on that engine, although I know for sure the early D-6s when thru some growing pains at those ratings , where as the QSB has never had any–Rock solid from DAY 1..

Understand, your engine is producing about 67 HP per liter at rated RPM & load .. Very high performance & in that manufacturing era was close to the top of it’s class………………………….

You came here for help, RIGHT?

Here it is—–You need to prop down to where your engine reaches NOT LESS than 3575 RPM and reaches it EASY with your vessel loaded for bear..

If your props SCAN at your numbers, that’s not less than 3″ of pitch GONE..

Last, remember this if nothing else–In general, in a vessel like yours, you cannot under prop engines like this, you can only OVER PROP THEM.

And that applies to all colors of them in this class, and especially so when you have way too much boat and barely enough engine…

Tony

[Author]

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