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Old 01 May 2007, 15:55   #11
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Well Ive done the hard bit which was cutting the transom, if this doesn't give me at least 5 knots it's onto ebay and then i'll be looking for a 5hp longshaft or do you think Ill need to go bigger, I just wanted to keep to the single pot smaller engine as once you go into the realms of 6HP plus its 2 pots and more weight?

Chris
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Old 01 May 2007, 16:54   #12
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Originally Posted by Chris1573 View Post
Well Ive done the hard bit which was cutting the transom, if this doesn't give me at least 5 knots it's onto ebay and then i'll be looking for a 5hp longshaft or do you think Ill need to go bigger, I just wanted to keep to the single pot smaller engine as once you go into the realms of 6HP plus its 2 pots and more weight?

Chris

6hp Johnson 4 stroke long shaft (prop is clear of the hull) gives me about 4.3 to 4.5 knots on mine (Humber Destroyer 5.8m) but doesn't reach anywhere near max revs - I think it is hitting the hull displacement speed which at the square root of the waterline in feet, in theory on mine should be ~ 4.36kt. I have seen over 5kt on brief spurts but I think probably with "help" from water movement. I reckon your target is optimistic based on my (albeit limited) experience.
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Old 01 May 2007, 17:05   #13
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Chris, if you want 5 knots I recon you need a 5 hp long shaft with an exhaust though the prop propellor rather than the solid one you have at the moment, but try it first.

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Old 01 May 2007, 17:24   #14
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Chris, if you want 5 knots I recon you need a 5 hp long shaft with an exhaust though the prop propellor rather than the solid one you have at the moment, but try it first.

Pete
Which 5 HP engines have a through prop exaust Pete?

Chris
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Old 02 May 2007, 04:11   #15
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Which 5 HP engines have a through prop exhaust Pete? Chris
Chris, have a look at the 2 stroke 4-5 hp Merc, Mariner and Tohatsu engines. From memory I think the 5hp has the ability to switch from internal tank (little one on top) to external red tanks whilst the 4 hp doesn't.

http://www.boatsandoutboards.co.uk/view/F119838/

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