Drop in Speed throughout the powerband

R

redman

New member
How much of a drop in speed is "normal" with a hull that's been in the water for the past 7 months? (Chesapeake, Anacostia, Potomac). Am without a tow vehicle so not that simple to pull out of the water and clean the hull. I talked with a local Marina... described the problem and the performance of the engine (still able to reach top end RPMs (approx 5400); no hesitation in engine response transitioning from hull speed to planing; and no problems starting). Marina rep thought it was a fouled hull.

For background: Top speed by GPS was 28.9 knots, in June... now it is no more than 21 knots. I like to poke along at 14-16knots and don't normally "open it up"... got that urge out of my system a while ago. I thought it was the engine (Honda 90) but the Marina rep couldnt support that based on what I've described here and to him. I checked the Honda website and based on the speed chart for the 90 I am about 3-4knots slower than the posted performance starting at 3500 rpm. They post mph... I've done the conversion and am still not up to spec. compared to the 17" prop.

Any thoughts or insight on what is causing the drop in performance is appreciated! It's sort of puzzling, and like most mechanical things (not a mechanic), will be a simple fix. Have found a tow vehicle to use this Saturday, will pull the boat, powerwash the hull and hope for the best, even though someone once said "hope is not a good strategy." Look forward to your comments.

Mike on C-Tour
 
I'd wager that a good cleaning will put you back to code. A dirty bottem makes a heck of a difference.
Seven months is a pretty long spell if you don't have any bottem paint, the stuff growing down there might scare you. You might want to swing by the local marine supply store and pick up some hull cleaner to make the washing a bit easier.....maybe pick up a few of those "will work for food" people also :)
 
We've been having a diver clean the bottom of ours every 3-4 weeks....but we will be changing the prop as soon as we pull the boat to get the recommended WOT RPMs up to where they're supposed to be, so haven't really "lost" anything in speed...didn't have it to begin with! :mrgreen:
 
B~C wrote:

"maybe pick up a few of those "will work for food" people also"


You probably could feed them barnacle and zebra mussel sushi along with tossed marine salad greens la du' Okefenokee.

Those goodies are generally better for brunch than boatspeed.

Be sure to pressure wash the bottom ASAP when you pull the boat. If you let the critters dry out, they get doubly hard to remove.

Joe.
 
When my sailboat was in a slip in Florida a diver cleaned the hull every month.

Sea Wolf is right, get it pressure washed IMMEDIATELY upon retrieving.

Even 3 or 4 hours seems to make a difference, and if it dries you will spend a lot of time and get sore hands cleaning the bottom.

Been there, done that. Only once though. :)
 
Most of the yards, at least in the pacific northwest, will have a pressure washer at the ready as the travellift moves away from the water. They go maybe 100 feet and hit it with the washer. Letting a bottom dry without it would be the short cut to arthritis.
 
You might also consider the possiblity that you've added weight (to the boat :smilep ) since you last ran it at WOT. It's easy to add tons of weight and not realize it as you stock your cubboards ect... Having said that, 21 knt's does seem a tad low.
 
Hi Folks,

I don't know what the temperature of the water is in Virginia this time of year, but in the summer in Nantucket, I clean the bottom with a stiff brusk and scraper. I just duck under and work the bottom. I do it along the beach with the boat about chest high. Little work but works for me.

You could use a stiff brush with a long handle and get the same results.

Good luck.

Fred
 
Thanks everyone for the insight... I think tomorrow will be a learning experience. Will stop at West Marine to get the cleaning equipment... maybe bring a lawnmower too! "Mow that bottom" Yikes... gonna be ugly :embarrased. Will give a report Saturday or Sunday.

Thanks again.

Mike on C-Tour.
 
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