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valerio posted 02-19-2004 04:32 AM ET (US)   Profile for valerio   Send Email to valerio  
hi guys, i'm writing from italy. i have just purchased in usa an used 28 conquest of 2000 with 2 x 225 optimax. used the first time last suturday and very disappointed about the performances. taking off from the water only a 5000 rpm and running at 28/30 knots with 4800/4999 rpm. too much in my opinion and as written everiywhere into the magazines. very high consumption of gasoline. all the measures (trims, tabs, etc...) had no efficacy to change and ameliorate the performances. sea perfect, no wind, only 2 persons on board, half tank. so ideal conditions. engines are perfect and checked by mercury. props are also perfect. cannot understand these performances. can someone help me please ? hanks. ciao from Italy !
valerio posted 02-19-2004 10:26 AM ET (US)     Profile for valerio  Send Email to valerio     
sorry, I have realized that (may be) I have posted on the wrong topic. I am new. sorry. in case, please, suggest to me where I have to post. thanks.
Tom W Clark posted 02-19-2004 10:40 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

This is certainly the most appropriate forum for performance questions.

I am unclear on what you are asking. You say the maximum RPM of the engines at wide open throttle is 5000. You think this is too high? I would think it is too low.

valerio posted 02-20-2004 06:55 AM ET (US)     Profile for valerio  Send Email to valerio     
Hi Tom, many thanks for your kin confirmation I am on the right topic. I will try to explain better myself. Sorry. my english is not good enough for such technical questions, but I will try....
1 - reading the magazines I see that the conquest 28 shoud plane (falls of) in 11 seconds and 3500-3800 RPM, insetad my boat needs to run the engines at 5000 rpm !
2 - cruise speed of 28/32 mph should be maintained with the 2 engines at about 4200/4300 rpm. instead to mantain this speed I need to remain at 5000 rpms and this is too much in my opinion.

I know, the engines can go up to 5800 rpm. Boston say that with 3-blade Mercury Mirage Plus 15.5 x 17P prop (my props) I could reach a speed of 45.4 mph running at 5800 rpm (WOT). But I didnt reach this speed, absolutely.
So I looking what is wrong, assuming that the engines and props are perfect (as the assistance of Mercury say 1).

Let me have some ideas to find the problem and solve the issue. Thanks so much. My best regards from Italy

Plotman posted 02-20-2004 08:04 AM ET (US)     Profile for Plotman  Send Email to Plotman     
The first thing that comes to mind is how clean is the bottom. If it has been in the water a while, you may have all kinds of growth down there which could really hurt performance. Can you pull it or go down into the water to check?

Also remember that mph and knots are not the same thing: 1 knot = 1.15 mph.


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