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02-09-2013, 09:22 PM
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#1
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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Weight of a 200/225/250 merc optimax flywheel
My lightened and balanced flywheel has just arrived and weighs 6.6kg.
Anyone know what a standard 200/225/250 optimax flywheel weighs?
Thanks Dave
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02-09-2013, 11:04 PM
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#2
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BAD HABIT
Country: FRANCE
Interests: speed on water/technics
Boat make: INVADER
Engines: MERC 250XS/SM 1.62
Cruising area: south Britany
Join Date: May 2007
Posts: 562
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Optimax flywheel weight
for 300 XS
283-859619T04 FLYWHEEL = 20.09 Lbs
For 250XS
283-859619T1 FLYWHEEL = 16.45 Lbs
CNC lightweight flywheel from Simon's & Dave Bush made in aluminum alloy are only 6lbs ...
http://www.davebushracing.com/optima...rformance.html
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02-09-2013, 11:34 PM
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#3
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Registered User
Country: UK
Location: Surrey
Occupation: Motorsport Development inc Engine Managment
Boat make: 21ft
Engines: Various
Cruising area: Solent / Kent / Cornwall
Join Date: Oct 2011
Location: Surrey
Posts: 375
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Do these (light) flywheels actually make a difference? Its not like on a car where you can go from idle to max rpm within a couple of seconds or less...
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03-09-2013, 06:52 AM
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#4
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BAD HABIT
Country: FRANCE
Interests: speed on water/technics
Boat make: INVADER
Engines: MERC 250XS/SM 1.62
Cruising area: south Britany
Join Date: May 2007
Posts: 562
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weight effects on outboard flywheel
Here a good discussion on the subject, especialy from Jay racing.
http://www.screamandfly.com/showthre...ht+flywheel+XS
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03-09-2013, 08:27 AM
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#5
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Registered User
Country: UK
Location: Surrey
Occupation: Motorsport Development inc Engine Managment
Boat make: 21ft
Engines: Various
Cruising area: Solent / Kent / Cornwall
Join Date: Oct 2011
Location: Surrey
Posts: 375
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Exactly as I thought. Thanks
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03-09-2013, 02:50 PM
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#6
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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Hi Beyondhelp, I use to race Thundercats and removing the ring gear on a tohatsu 50hp made a big difference on acceleration times. You could here the difference on the muffs, the engine use to rev quickly like a motorbike.
You also gain a few extra revs at top end, which on very close racing, made the difference between a win or a loss.
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03-09-2013, 02:57 PM
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#7
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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For me the difference is simple I have a prop I like but it only revs to 5300 the engine revs to 6000.
The most a depitched will give me is about another 250 revs. Which brings me to 5550 revs, a new prop is £300-400 the flywheel was £120 delivered to the door and should give me another 250 revs.
So basically cheaper and I go slightly faster for my money.
Some people might say why bother, but the revs drop the more people are on the boat and your putting more strain on the motor running over pitched.
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03-09-2013, 04:38 PM
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#8
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Registered User
Join Date: Sep 2007
Posts: 513
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Quote:
Originally Posted by Banana Shark Dave
and I go slightly faster for my money.
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Can't see that myself. I'm sure the motor will be slightly more responsive, but why would it be quicker?
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03-09-2013, 05:19 PM
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#9
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Registered User
Country: Guernsey
Occupation: Postie
Interests: Heavy Heavy Metal
Boat name: Slayer II, Slayer, Pen15
Boat make: Phantom 19G-R, Bernico F2 Extreme, Ring 15
Engines: Evinrude 115HO, Yam 90
Cruising area: Channel Islands
Join Date: Aug 2009
Posts: 1,460
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I agree... I gained 400 revs easy with some prop work without losing any pitch
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03-09-2013, 05:41 PM
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#10
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Registered User
Boat make: Phantom 23
Join Date: Mar 2006
Posts: 1,693
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Light flywheel makes no difference to top end, it'll just accelerate quicker.
If your not making the revs, just buy a new prop, or have it worked, or move the engine up a bolt hole!
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03-09-2013, 07:51 PM
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#11
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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I beg to differ with our tohatsu 50hp engines they rev faster, and you gain a few hundred revs, granted not much but you do get some.
Going up a hole is out, cavitates to much.
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03-09-2013, 08:02 PM
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#12
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Registered User
Country: Guernsey
Occupation: Postie
Interests: Heavy Heavy Metal
Boat name: Slayer II, Slayer, Pen15
Boat make: Phantom 19G-R, Bernico F2 Extreme, Ring 15
Engines: Evinrude 115HO, Yam 90
Cruising area: Channel Islands
Join Date: Aug 2009
Posts: 1,460
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Out of interest, what prop? And what speeds do you see?
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03-09-2013, 08:22 PM
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#13
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Registered User
Boat make: Phantom 23
Join Date: Mar 2006
Posts: 1,693
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Quote:
Originally Posted by Banana Shark Dave
I beg to differ with our tohatsu 50hp engines they rev faster, and you gain a few hundred revs, granted not much but you do get some.
Going up a hole is out, cavitates to much.
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If we're talking about a 3.0L merc then I did it on sunday. Not the slightest difference in top speed.
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04-09-2013, 12:10 PM
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#14
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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Going out to test tonight, will put the results up later.
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04-09-2013, 08:33 PM
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#15
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Registered User
Country: UK
Location: Gosport
Occupation: Own a small building firm.
Interests: Boats, kids and looking after the Wife HaHa
Boat name: Shamu
Boat make: Banana Shark 770
Engines: Mercury XS300
Cruising area: Solent
Join Date: Aug 2013
Location: Gosport
Posts: 368
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Couldn't do a proper test as had the wife and 2x 7yr olds and 1x 5 yr old. Turned the same revs in a shorter space as previously with 2x adults. Some slight improvement.
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