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Old 09-08-2007, 10:48 AM   #1
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Gear ratios

Hi

I have a Revenger 25 with the Mercruiser 5.7 small block, when I bought the boat the leg ratio was to low but I do not know the exact ratio I had to use a Mirage Plus 27 pitch prop and the engine was running 4800-4900 rpm and about 55-57 mph on gps. Due to the leg being in poor condition I have now fitted a gen 2 with a 1.84 ratio which is still not ideal do I need to change the ratio to 1.50 to get the best performance or just change the prop pitch? If I donít change the ratio and just prop it to suit how much top end would drop off, I was told it should be running in the low 60's? I have not run the boat with the new leg but the engine is back in and the leg is ready to go on. Any input would be appreciated.
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Old 09-08-2007, 11:02 AM   #2
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As you say, the ratio isn't ideal, but to be honest, I can't see it making a huge difference,
I wouldn't really expect it to be any slower top speed, assuming you get the right prop, but you may suffer a little more torque-reaction in the boat with that ratio.

You say it has a small block, but you haven't stated what power you think it is.

Is the bottom clean? (antifouled, or nice & shiney)

Which R25 is it, SC or mediteranee? I actually think that if it's a 260, or 280hp small block, and you're seeing mid-late 50's, you're not doing too bad.

JF
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Old 09-08-2007, 11:37 AM   #3
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The engine started life as a 5.7 260 hp but it now has a 4 bolt main block and fitted with high performance exhaust and inlet manifolds, holy double pumper carburettor, MDS electronic ignition system, K&N Flam arrester and a performance cam. So not sure what it is producing now I hope it is now closer to 300 hp but have no idea. The owner before me said it was running 62mph with the standard motor but that was properly pub talk.

The bottom is clean no antifouling and it is the mediteranee. When I fitted the cam it did say for best performance is should be running 4400-4600 rpm but the 27p prop was the biggest I could get hold of so have never found out if that would help or not.

Are you still selling the 496 HO?
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Old 09-08-2007, 11:53 AM   #4
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Hi, the 496 would become available 'if' we decide that buying packages (complete motor/drive setup) and splitting them, is the cheapest way to buy drives/gimbles etc.

We haven't decided on that yet, so haven't actually purchased anything so far. If it goes that way, It'll be on here.

I really don't think late 50's it too bed for that setup. As you say, there's a lot of 'pub talk' in the boating scene, don't believe everything you hear in the bragging rights department.

Most people exagerate about their boats' performance, it's the law.
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Old 09-08-2007, 01:00 PM   #5
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Thanks for your input John.

I will fit the drive and give it a go and if anyone asks it's running 65 all day long!!!

Is there going to be another poker run I missed the last one as my boat was not ready.
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