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| 2x aq131, 4500rev, 18 knots, 31ft boat |
| Author |
Message |
    
Sebastian
Member
Username: sebski
Post Number: 16
Registered: 02-2008
| | Posted on Tuesday, May 06, 2008 - 05:39 am: | 
|
Hi Guys,
After few months fight with my aq131
I went yesterday to final sea trial,
everythink seems to be ok,
just one question,
she started planning at 16 knots,
and 18 knots was her max speed,
engine was reving 4500 and didnt want to go more.
Is it ok for this size of boat and that kind of engine?
If I would install trim tabs the necessary speed to get her on plane will drop much?
Sebastian |
Mike
Advanced Member
Username: mike77cj
Post Number: 127
Registered: 06-2007
| | Posted on Tuesday, May 06, 2008 - 11:28 am: |
|
What size propeller are you running?
Download the owner's service manual here:
http://www.volvo.com/volvopenta/na/en-us/marine_leisure_engines/engines/out_of_p roduction_engines/out_of_production_engines.htm
The max rpm for your engine is 4700-5000 rpm. Your current 4500 rpms is a bit low. I would recommend decreasing the pitch of your prop. two inches, ie. from a 21 to 19, or 19 to 17.
The following website is also helpful in calculatting 'theoretical' boat speed:
http://www.rbbi.com/folders/prop/propcalc.htm
The gear ratio on your drive is 2.15:1, btw. |
El Pescador
Senior Member
Username: el_pescador
Post Number: 3098
Registered: 02-2006
| | Posted on Tuesday, May 06, 2008 - 09:08 pm: |
|
Make sure the trim pin is in the right position in the transom shield (usually the middle hole). Trim tabs should both decrease the time to plane and the speed at which a boat planes.
What are the diameter and pitch of the props you are currently using? |
Sebastian
Member
Username: sebski
Post Number: 17
Registered: 02-2008
| | Posted on Wednesday, May 07, 2008 - 03:28 am: |
|
I am using hole first one near the transom, but still bow is tending to be too much up...
Propellers are 15x15 |
Mike
Advanced Member
Username: mike77cj
Post Number: 130
Registered: 06-2007
| | Posted on Wednesday, May 07, 2008 - 07:47 am: |
|
I think you should be spinning more than 4500 RPM @ WOT. How tired are your engines? Have you done a compression check? Have you ensured the butterflies open fully when you are @ WOT?
You could decrease to 14x15 to pick up a few hundred RPMs, but it will not effect your top end speed.
Also, I would advise adding trim tabs. You will notice a large difference. |
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