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Rank: Dedicated Tin Star
Groups: Member
Joined: 12/10/2007
Posts: 68
Points: -907
Location: Lake of the Ozarks, Mo.
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I've always wondered how noisey Sea Turtle is to people on shore. A couple of years ago I put new Super II fiberglass mufflers on her. 24" long 10" d. While taking the boat out of the water for the season last week, I had my neighbor run by me (with me on the boat ramp) at 3500 rpm. :d/ I was very pleased at how quiet it was, even going away with the stern pointed directly at me. It's noisier in the cockpit. At 3500 it is quite noisey. I have the drive shaft lined up very well. I noticed that if I move out from under the hard top toward the stern, its quieter. There is a anti vibration system that is available to install between the drive shaft and the xmission. It is the Aquadrive anti-vibration system available from www. mackboring.com. Their desctiption sounds like just what I need except it it very pricey. Since most of my running is around 1500 which is quiet running, I will pass. Here's a pic of the noise sea trial, Looks like the neighbor insn't using the trim tabs. cheers y'all
clarko attached the following image(s):
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Please Register : New members may not post until approved. An email is sent after approval. We do this to reduce those who use these forums for spamming.
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Rank: Top Rank Aluminum Star
Groups: Member
Joined: 12/7/2007
Posts: 394
Points: 726
Location: Central Florida and the DC area
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There is a good chance that you can't use an Aquadrive because there isn't enough room between the transmission tailstock and the stuffing box.
The Aquadrive is a short shaft with a CV joint on each end, that drives the shaft even if the engine is out of alignment.
My old boat had its diesel mounted level (for fit), and used such a shaft to couple to the propshaft which is at a 14 degree incline. I didn't spend thousands to get one from those guys, I mounted a thrust bearing for the shaft on a crossmember and got a halfshaft from the junkyard for 30 bux, from a Cadillac, I believe. It helps to have a lathe and a milling machine if you are going to do this sort of thing.
What will fit is one of those rubber donut things that absorbs shock in the shaft, highly recommended. Doesn't let you use soft engine mounts, but you shouldn't really have a vibration problem coming from the engine itself.
"I remember when welfare was for poor people..."
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Rank: Top Rank Aluminum Star
Groups: Administration
, Member
Joined: 12/5/2007
Posts: 981
Points: 1,793
Location: New Tripoli, PA
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Definitely needed some "bow down". I'm amazed at how much my 32 footer "wants" in this respect. using the GPS, I've learned to tweak the trim tabs until it appears that the bow is way too low, yet speed picks up! Wouldn't have believed it without seeing it.
On the vibration problem, IF you have everything nice and lined up--and the shaft isn't bent--then that's all you can do. Those anti-vibration deals are come under fire for wearing out stuffing boxes; they either allow the shaft to flop around, or to push it off to one side. And if the shaft is shoved too much to one side, the shtuffing box will be destroyed along with the shaft log as well (which means down she goes!)
Finally, inboards make vibration--period. Can't get away from it. Why? Shock waves radiate out from the prop in all directions, and when they hit the hull above you get a vibration. The alternative is a stern drive--the anti-cavitation plate above the prop doesn't react as harsely to the shock waves--or the up and coming surface piercing drives.
Jeff
I'm STILL waiting for my bailout!
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Rank: Upper Crust Bronze Star
Groups: Member
Joined: 12/7/2007
Posts: 125
Points: 161
Location: Alpena, Michigan
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As my  is equiped with an I/O, and the engine is sitting back by the transom, I am building a wooden box around the engine below decks (with the good parts of the decking I pulled up) and plan on insulating the inmside with some foil type insulation. With all the room Marinette's have below their weather deck the engine noise reverberates like a drum. I am also planning on insulating the aft side of the bulkhead between the forward engine compartment and the lower aft cabin area and the bottom side of the weather deck.
" LIFE is what happens to you, while your making other plans."
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Rank: Upper Crust Bronze Star
Groups: Member
Joined: 12/7/2007
Posts: 125
Points: 161
Location: Alpena, Michigan
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Jeff,
Thanks for your observations, I did not know if that held true for planning hulls. I remember reading that nautical architects try and build go-fast boats with as long as a water line as possile (Think rowing shells).
This seperates the bow wake from the stern wake by as much as possible. For some reason when these two wakes meet the drag created increases exponentially or there abouts. This is the advantage catamarans have over displacement or planning hulls. So more bow in the water = longer waterline.
"LIFE is what happens to you, while your making other plans."
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Rank: Top Rank Aluminum Star
Groups: Member
Joined: 12/10/2007
Posts: 185
Points: 567
Location: Lake Michigan
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My port muffler may have a broken baffle inside.
When I start them up the echo off the opposite seawall is much louder for the port than the starboard.
Peter
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Rank: Dedicated Tin Star
Groups: Member
Joined: 12/10/2007
Posts: 68
Points: -907
Location: Lake of the Ozarks, Mo.
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 Once again this sight has proven it's worth. Thanks gentlemen for your input. Sea Turtle sits on her trailer now and is ready for the winter cover. I'll wait for thanksgiving when the relatives are here, they can help me pull the plastic over. I have used a silver tarp for a cover. It cost about $125 for a 30x40 piece. It started falling apart in two years. I now use the thickest mil I can get of black plastic from the lumber yard. $70 for a 30x100 roll. It has lasted two years and still going strong and I have enough on the roll for another cover. We aren't cheap Jeff, just thrifty :d/ Something I would like to do is to determine mileage of the boat. I got the rpm/mph some time ago I believe from John's site. Using a handheld GPS. Sea Turtle operated very close to those figures so that indicates the engine is running strong, and the prop is right. WOT is 4000. Since I dont have a fuel flow indicator and don't plan to invest in one(thrifty), I have thought of taking a 1 gal can and tapping into the fuel line and run until the 1gal runs out and again using the GPS, determine distance. anyone have any other ideas to do this?
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Rank: Top Rank Aluminum Star
Groups: Administration
, Member
Joined: 12/5/2007
Posts: 981
Points: 1,793
Location: New Tripoli, PA
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..."I have thought of taking a 1 gal can and tapping into the fuel line and run until the 1gal runs out and again using the GPS, determine distance."
Crude, but it would be effective. Just be sure you don't spill gas and blow yourself up.
Jeff
PS: I have twin engines and ONE flowmeter. Thrifty, man!
I'm STILL waiting for my bailout!
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