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TOPIC: Never thought that a "dirty" hull could have so much performance effect

Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 12:43 #1

  • RobMick
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I have always taken pride on having clean "stuff", cars, house, tolls, equipment, watercraft, etc. When I hear members talk of a "dirty" hull I picture some guy's boat that has been moored in the water for the entire season and basically has "fur" growing off to the entire underside of the hull. We live on a fresh water lake, boats are about 100' from my door and this season I have kept my 185 in the water as I am using the lift for my pontoon...that's a whole other story. But we run the 185 regularly, and regularly I clean the crap that the hull attracts in the water. Yesterday I took the boat out by myself for a change and was able to put the throttle down for a bit and let that massive 3.0 ;) :whistle: stretch her legs a bit. The "admiral" likes to stay about 3200 rpm all day. Anyway, I pinned the throttle to the dash and could only get to 4000 rpm and 31 mph via gps. Both directions on the lake. I was really terrified that something major was wrong and envisioned losing her to my mechanic for the rest of the season. I anchored at my swimming hole, and while in the water simply used a non-scratch pad on the freeboard and as much of the underside of the hull as I could reach while hanging onto the rubrail of the boat. The hull had some discoloration and what I call some grime on the underside of the hull. Certainly no "fur" but you could feel the "roughness" of buildup. I scrubbed as much as I could reach. On the way back home, I again pegged the throttle to see if it helped.....OMG...same lake, same conditions, same payload....I reached my wot number of 4750 rpm and gps speed of 42. She still had a little left could probably get 44 but ran out of lake. Both directions she ran identical.

So I can attest that the "dirty" hull is a HUGE factor in performance. I never in my wildest dreams thought that what I deemed as minor buildup could affect the boat that much. Just wanted to share as I am sure others have had the picture of a "dirty" hull as I had.

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Hell, Michigan (yes we really live in a city named "Hell" in Michigan)
2012 BR 185 - 3.0 TKS
1999 Chaparral 233 Sunesta Ltd., 5.0 Volvo
1985 Harris Flotebote Classic 240
1993 Yamaha Waverunner III VXR
1993 Yamaha Waverunner III
1995 Yamaha Waverunner III GP
1995 Yamaha Waverunner III VXR PRO

Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 13:48 #2

  • mjoseph20
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I had the same issue last season. I lost 10-12 mph off my WOT speed due to freshwater lake growth. This season, I purchased a boat scrubbing brush on an extension wand, which I use to scrub the bottom of the boat every weekend. Just a few minutes of scrubbing on all areas I can reach makes a difference.

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Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 15:11 #3

  • 706jim
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My 18' Starcraft Holiday would hit about 43. After 6 weeks in not that warm river water 31 would all it would go. Interesting that our numbers are nearly identical. Anti fouling paint helped a lot. Although just leaving the boat overnight on the land fixed the problem

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2007 Discovery 246
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Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 15:20 #4

  • davesisk
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I get my Bayliner 3818 bottom and running gear cleaned by a diver each month. Immediately after cleaning, she'll cruise at around 15 knots...by the end of the month, cruise speed drops to around 12 knots.

Dave

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Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 21:14 #5

  • Back2Water
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Thanks for posting these real life examples. I have to say that I always knew a dirty bottom could affect performance, but never would have guessed it would have this great of an impact! Great info. Thanks again!

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David W. PDX, OR
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Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 21:18 #6

  • businessgetmoney
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I want to try this for the heck of it. I dont get growth.. i power wash before i launch but boaty has been in river slip all season so far...

I have black anti foul paint, its naturally rough to the touch. Theres not much build up on it. If you thouch it, you get horrible black almost oil charcoal on you that doesnt come off...

Ive read acids (snobowl) are great for cleaning bottums. Will that take the black char mess off and clean me up? Ive never cleaned it otherwise, just a thorough powerwash beginning and end of season

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
2014 "searay" tandom trailer

Anchor bay clinton river
Michigan

Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 23:44 #7

  • RobMick
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businessgetmoney wrote: I want to try this for the heck of it. I dont get growth.. i power wash before i launch but boaty has been in river slip all season so far...

I have black anti foul paint, its naturally rough to the touch. Theres not much build up on it. If you thouch it, you get horrible black almost oil charcoal on you that doesnt come off...

Ive read acids (snobowl) are great for cleaning bottums. Will that take the black char mess off and clean me up? Ive never cleaned itotherwise, just a thorough powerwash beginning and end of season


Good questions regarding the toilet bowl cleaner/acidic cleaners that do so well on my unpainted hull. I have thought about bottom paint for our 185....I can't stand the water stains..rust stains from being moored. Boat might look sharp with some matching red bottom paint. Or I could just get another covered boat lift...B) ;)

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Hell, Michigan (yes we really live in a city named "Hell" in Michigan)
2012 BR 185 - 3.0 TKS
1999 Chaparral 233 Sunesta Ltd., 5.0 Volvo
1985 Harris Flotebote Classic 240
1993 Yamaha Waverunner III VXR
1993 Yamaha Waverunner III
1995 Yamaha Waverunner III GP
1995 Yamaha Waverunner III VXR PRO

Never thought that a "dirty" hull could have so much performance effect 01 Aug 2017 23:54 #8

  • businessgetmoney
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The acids will strip any wax you have. I use snobowl because its so cheap. Use it for cleaning fiberglass showers of soap scum and rust stains... almost no scrubing.

I just dont know how it affect bottom paint

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1993 formula pc 31 twin 454 bravo 2
1989 2655 cierra 5.7 omc cobra
2014 "searay" tandom trailer

Anchor bay clinton river
Michigan
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