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Old 02-10-2020, 12:51 PM   #1
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City: Kemah, TX
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Vessel Name: Blue Tortuga
Vessel Model: Mainship 400
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2004 Mainship 400 speeds and RPM with single Yanmar 370hp.

Mainship 400 owners, Would you share your Single Yan 370 hp, speeds and at what RPM (ang GPH if you know) with me.

My boat seems to be 1-1.5 knots slower what is found on the Stella Blue and original mainship site as far as the speed and RPM tables.


Like they show 2000 rpm getting 8.3 knots. My boat at 2000 rpm I am lucky to get 7 knots. I've got to get to 2500 to hit 8 knots and they show 9.5kts

Also before you ask, I have:
New Bottom, shaft, coupler, PSS shaft seal, Cutlass bearing, even new Trim tabs.
Prop removed and balanced.
Prop speed on shaft and prop.
Rudder dropped etc.
The bottom is as close to factory new as it can be.

The Yanmar runs fine up to WOT and will hit 12.9 knots with tabs down but no where near the 16.7 knots that is shown in the tables.

I would appreciate knowing if others see the same as I do or do I have something else I need to look at.
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Old 02-10-2020, 01:01 PM   #2
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What rpm do you get at full power? I like to shoot for 3350-3400 on the 6LY. Note also the Yanmar analog tachs can be quite a bit off. Really need to photo tach.

How much stuff do you have in the boat? Dink? Lots of stuff? Weight really eats speed.
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Old 02-10-2020, 01:05 PM   #3
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City: Savannah, Ga.
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Vessel Model: 2006 Mainship 400
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I usually go about 8.5 knots at 2100 RPM with my 6LY2AN-STP 440 hp, (dif engine but maybe a reference point)
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Old 02-13-2020, 01:39 PM   #4
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City: Kingston Ontario
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Quote:
Originally Posted by Blue Tortuga View Post
Mainship 400 owners, Would you share your Single Yan 370 hp, speeds and at what RPM (ang GPH if you know) with me.

My boat seems to be 1-1.5 knots slower what is found on the Stella Blue and original mainship site as far as the speed and RPM tables.


Like they show 2000 rpm getting 8.3 knots. My boat at 2000 rpm I am lucky to get 7 knots. I've got to get to 2500 to hit 8 knots and they show 9.5kts

Also before you ask, I have:
New Bottom, shaft, coupler, PSS shaft seal, Cutlass bearing, even new Trim tabs.
Prop removed and balanced.
Prop speed on shaft and prop.
Rudder dropped etc.
The bottom is as close to factory new as it can be.

The Yanmar runs fine up to WOT and will hit 12.9 knots with tabs down but no where near the 16.7 knots that is shown in the tables.

I would appreciate knowing if others see the same as I do or do I have something else I need to look at.
We have Mainship 390 with the single Yanmar 370 HP Totals for 2019 are as follows
.46 US Gallon per Nautical Mile 3.02 US Gallons per Hour Average speed 6.76 Knots average RPM 1996.3 Distance travelled was 509 38 NM with 77.94 Engine hours used. we have an 8KW Generator but only put less than 4 hours on it
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Old 02-23-2020, 08:23 AM   #5
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City: Sint Maarten DWI
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Vessel Name: Au Naturel
Vessel Model: 2000 Mainship 390 Trawler
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I have a 2000 390 with single Cat 3161 diesel. Bottom just painted. I too am a bit confused on my performance data. I can run WOT at 2000rpm, and get 9.5 - 10.5 mph via my GPS. The 10.5 is with following seas and wind. I really thought it should be 12.5 or better. I am third owner, so don't know if prop was replaced or re-pitched from original. I am at 3/4 fuel tanks, and 3/4 water tanks. Any feed back from other 390 owners with same/similar engine? I realize the 3161 is just a 300hp.
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Old 02-23-2020, 08:25 AM   #6
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City: Sint Maarten DWI
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Also, at 1600rpm she will cruise at 7.5 -8.5mph.
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Old 02-24-2020, 11:15 AM   #7
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City: Kemah, TX
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All,
Thanks for all your replies. I did have enough time to really get out and run my boat for some extended period of time. At 2200 rpm, we were hitting 8.1 knots but it takes awhile to get up to that. So maybe the official numbers are not that far off.
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