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Old 09 June 2004, 11:39   #11
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Humber Rib repower

Martin

I have a Humber 5.5 Destroyer with a 130hp Yamaha 2 stroke.

Top speed with light load so far 43 knots, with waves no more than a foot. A small chine walk began to develop so I will be making a few small adjustments. With flat water I expect there is some more speed say 45-46 knots.

It's early days with this set-up but the max speed achieved with the same load from our Johnson 90 2 stroke prior to the upgrade was 38.6 knots.

Both engines had a 19 pitch prop.

Where the real difference is noticed is in sheer power when accelerating.

Hope this helps.

John
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Old 09 June 2004, 15:10   #12
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"A small chine walk began to develop so I will be making a few small adjustments".



What adjustments wiill you make?My assault chine walks when trimmed right up at the bow if there are any notable waves and WOT(about 40 knots),I have a 21" propeller,and the engine pulls 6000-6100 revs,I was thinking of getting another propeller of the next pitch up for economy if nothing else.Will this make any difference to the chine walking or should I just not trim up so high?The chine walk disappears as soon I trim down or back off the throttle.
The engine WOT range is 5000-6000,the dealer says I should keep the prop I have as the engine should run as close to 6000 rpm as possible.
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Old 09 June 2004, 15:36   #13
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What adjustments wiill you make?

I am told by my engine service man that the trimtab is the first place to look.

John
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Old 09 June 2004, 15:52   #14
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Hmm Optimax! They really are a good unit and so cheep to run.
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Old 09 June 2004, 16:04   #15
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Thanks for all of the suggestions. Having spoken to a couple of engine guys today I might stretch my budget a bit more so its between four stroke and new tech two strokes, but I do not want to start a debate on that front I am sure that there are plenty more threads on that!

150hp optimax sounds great, but may be just too much power.

What I want to do is cruise comfortably at 30 kts and push towards 40kts occasionally, whilst keeping some degree of economy. There is no point putting too much power on the boat as there are few times when the conditions allow you to run fast for extended periods.

Mmmm must keep pondering on this one. Any more suggestions appreciated.

Martin
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Old 09 June 2004, 16:21   #16
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Quote:
Originally Posted by timboli
....or should I just not trim up so high?The chine walk disappears as soon I trim down..
There's your answer. Just a tad will increase the waterline length and bring back the stability.

Make sure you have NO play in the steering and/or bearings and the engine mounts must be good.

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Quote:
Originally Posted by Martin
...150hp optimax sounds great, but may be just too much power...
Nope, 150 will be good.
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Old 09 June 2004, 17:43   #17
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Any ideas what fuel consumption is on a 150hp Optimax? I know it will vary depending upon sea conditions, load etc, just after rough estimate.

Martin
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Old 09 June 2004, 17:48   #18
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Quote:
Originally Posted by Martin
Any ideas what fuel consumption is on a 150hp Optimax? I know it will vary depending upon sea conditions, load etc, just after rough estimate.

Martin
this link http://www.yamaha-motor.nl/products/...ws/article.jsp
which I posted on another shows consumption in relation to other 150 ies


not as good as the 4 strokes
hope it helps

P
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Old 09 June 2004, 17:55   #19
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Thank you, I will look now.


Martin
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