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Old 07-24-2018, 01:49 AM   #1
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Default Maxum 3300 WOT

Hi Guys

I've got a new to me Maxum 3300 with Mag 350's. WOT on the boat is currently 4000 with a top speed of 35 mph. She gets up on the plane around 3100 revs at 27 mph which seems OK.

This seems on the low side as others are getting 4800 - 5200 from these engines and a much higher top speed.

The hull has just been cleaned as have the stern drives. The boat does have a full tank of gas at the moment but I'm wondering if the previous owner has been running props with too big a pitch or if the engine just needs a proper tune up. I can't actually tell the pitch of the current props because they are no markings left on them but they are in good condition.

The engine oil has just been changed and that has not affected the WOT. I've booked the boat in for a full engine service so that may help.

I'm not too concerned with top speed but I would like to maximise fuel economy and I suspect I'm not able to do that with the current set up.

Can anyone give me any recommendations please in terms of best props for this boat or anything else I should check?

Many thanks

Nalin
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Old 07-24-2018, 02:08 AM   #2
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WOT should be 4400-4800. What drives do you have? Some props have the part number on the hub and cannot be read when installed.
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Old 07-24-2018, 02:38 AM   #3
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Thanks Mike. I've got Bravo II's.

I'll ask them to check inside the hubs when they take them off.
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Old 07-24-2018, 04:54 AM   #4
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Quote:
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Thanks Mike. I've got Bravo II's.

I'll ask them to check inside the hubs when they take them off.
What is the ratio from your drive?
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Old 07-24-2018, 04:56 AM   #5
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HI Gugi.

Sorry I have no idea!
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Old 07-24-2018, 11:24 AM   #6
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I would look into dropping the pitch down one size.
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Old 07-24-2018, 12:01 PM   #7
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Quote:
Originally Posted by Nalinjay View Post

This seems on the low side as others are getting 4800 - 5200 from these engines and a much higher top speed.
All Mercruiser engines are between 4400 - 4800 at MAx. RPM.

Are you trimming the drives out once you're up on plane?
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Old 07-24-2018, 03:28 PM   #8
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Call Hill Marine. They are great to work with and will dial in the props you need. They are great about letting you try props until you get them right but usually they recommend the best ones the first time.

https://www.hillmarine.net/Articles.asp?ID=83
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Old 07-24-2018, 05:40 PM   #9
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Thanks Mike
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Old 07-24-2018, 05:41 PM   #10
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Thanks Shrew. I must admit I haven't played around with the drive trim, just the trim tabs. If 4400 is about Rigg for these engines then trimming out the drives may get me th ere
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Old 07-24-2018, 05:42 PM   #11
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Cheers Philbo. I'll give them a call
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Old 07-25-2018, 01:25 PM   #12
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Quote:
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Thanks Shrew. I must admit I haven't played around with the drive trim, just the trim tabs. If 4400 is about Rigg for these engines then trimming out the drives may get me th ere
Use as little tab as possible. Once on plane, start trimming the drives out slowly. With each click, you should see the RPM rise slightly. If you start to cavitate, then click back in until it stops. Right at the edge of cavitation is where your drives will be trimmed out optimally.
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Old 07-26-2018, 12:03 PM   #13
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Thanks Shrew. Much appreciated
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