Speed with a single 400 Mainship?

[Seevee]

Just wondering what other Mainship 400 single engine owners are getting to top end speed?


When I surveyed my current boat with a 370 Yanmar, I saw 15.5 knots at full power. Lightly loaded, however, and might have have a bit of current pushing us.


However, 3 years later, the engine still turns up full RPM, and with a clean bottom, also light weight, the most I see is about 12 knots and I'm no where near on plane, so would not work for a cruising speed.



For the most part, I just don't need speed, so not a major issue, but is there something I should be looking at? Or do most of you get similar.

 

[rslifkin]

Which engine does yours have?

 

[Seevee]

Which engine does yours have?

Geeze... how could I forget that..... fixed it, thx.


Yanmar 370, 6LYA STP

 

[bayview]

After you add all your stuff the boat probably weighs more than when it was surveyed. Fuel and water matter as well.
It doesn't take much weight to reduce top end.

Do you still hit proper WOT RPM? You might consider having the props checked .

 

[DavidM]

Steve Cyr, longtime Mainship 400 owner, has a website that gives tons of information: http://www.scyr.org/stellablue/specifications.html. He shows 13.4 kts at wot.

But that boat should never be run at that speed for any length of time of course. Also because at say 3,000 rpms which would normally be ok for that engine, the boat is climbing up over its bow wave and consuming more hp than the prop curve would indicate, you should not run it there either. As Steve points out it is a sub 10 kt boat. From Steve's data 8-10 kts is the sweet spot for that boat.

David

 

[Seevee]

After you add all your stuff the boat probably weighs more than when it was surveyed. Fuel and water matter as well.
It doesn't take much weight to reduce top end.

Do you still hit proper WOT RPM? You might consider having the props checked .

Bayview,
Should be "close" to the same weight.... but. Added two batteries, an inverter and the fuel is full. So could be 1000 lbs more. Would be surprised that 1000 lbs would affect the speed much on a 24K boat.



Props checked and in excellent shape.

 

[Seevee]

Steve Cyr, longtime Mainship 400 owner, has a website that gives tons of information: http://www.scyr.org/stellablue/specifications.html. He shows 13.4 kts at wot.

But that boat should never be run at that speed for any length of time of course. Also because at say 3,000 rpms which would normally be ok for that engine, the boat is climbing up over its bow wave and consuming more hp than the prop curve would indicate, you should not run it there either. As Steve points out it is a sub 10 kt boat. From Steve's data 8-10 kts is the sweet spot for that boat.

David

Great site, been there a bunch. I can't get to 13.4. However, even the sweet spot is a tad lower, close to 7 knots. 10 is just pushing a lot of water, but doable if needed, and take in the ~2200 rpm range vs ~2000 for 7 kts.

 

[bayview]

How did it get to 24kts from original 15?

 

[Bacchus]

Bayview,
Should be "close" to the same weight.... but. Added two batteries, an inverter and the fuel is full. So could be 1000 lbs more. Would be surprised that 1000 lbs would affect the speed much on a 24K boat.



Props checked and in excellent shape.

Larry
I can see a difference with 1000 lb extra load on my 34HT w same Yan engine. Different boat, higher top end (20 MPH) and a little lighter (20k) but 1,000 lb does make a difference for me.

 

[Shrew]

I have the Yanmar 6LPA-STP2 (315HP) in a mainship 350. That is very close in shape and weight than the 400 in hull length, beam and depth.

I get about 8 - 8.5 knots at 2400 rpm. I'd be lucky to get 10 -11 knots at 3,000 rpm.

 

[Seevee]

How did it get to 24kts from original 15?

24K... 24,000 lbs, not knots. Should have made that clear.

 

[danderer]

Years ago I chartered one with a 380 Cummins. 12 knots was the top end.

 

[PM]

Mostly it is the weight you have on board, but also a lot depends on weight distribution.

Evaluate the following weight questions:

1) Where is your toolbox and how much does it weigh?
2) Fuel and water?
3) Dinghy and dinghy engine?
4) Waste tank?
5) Food and beverage?
6) For the first few months you owned the boat what do you remember hauling down the dock and onto the boat?
7) What exactly do you have in all the drawers and cabinets in the "V" berth? I suspect this is where you will find your solution.
8) What is in your lazaretto?
9) What about the Admiral, Fido and the kids?

pete

 

[Seevee]

Mostly it is the weight you have on board, but also a lot depends on weight distribution.

Evaluate the following weight questions:

1) Where is your toolbox and how much does it weigh?
2) Fuel and water?
3) Dinghy and dinghy engine?
4) Waste tank?
5) Food and beverage?
6) For the first few months you owned the boat what do you remember hauling down the dock and onto the boat?
7) What exactly do you have in all the drawers and cabinets in the "V" berth? I suspect this is where you will find your solution.
8) What is in your lazaretto?
9) What about the Admiral, Fido and the kids?

pete

Pete,


Good point. When we did the loop we had more stuff that one could imagine. Took several days to just load it and really didn't expect and performance with that extra weight.



But removed all of it when we finished, but probably still have a few extra things hidden that I can't find.

 

[markpierce]

If one cruises at one knot below hull speed, there is less worry about fuel consumption

 

[Dougcole]

Our 400 has twins, so not exactly the same but we top out at a little over 19 kts, lightly loaded with a clean bottom.


That said, I notice a big difference in our boat based on load and conditions. Heading east to the Bahamas this summer, with a month's worth of food, beer, two paddle boards, dinghy fuel, water maker, fishing tackle, freedive gear etc. pretty calm conditions but angling SE (St. Lucie Inlet to West End) across the gulf stream, we were getting about 12.5 knots at 2850 rpm. At that speed I normally get 14 to 15 knots.


Did you have your tabs all the way down? Are they operable? That makes a BIG difference for my boat, at least a knot. With no disrespect intended to Pete, who brings up a good point about load placement, I notice on the 400 that it runs better when it is flatter. I'd actually like to try moving some weight forward in my boat to counteract all the weight aft from most of the stuff I listed above.


Anyway, sorry to highjack your thread, I don't want it to turn into twin vs. single, but I thought the info might help.


Best,

 

[bayview]

IMO 12 or 15 kts doesn't matter as both will not be fully on plane anyway.
If you are still reaching rated RPM then one possibility other than weight is prop tuning. It is amazing what a difference a properly tuned prop can make.

 

[Capt Mike]

12 KTS is about all I can get out of my 2004 MS 400 with a single 370 HP Yanmar. I noted the same when we first purchased the boat last year, I was thinking top speed was closer to 14 - 15 KTS. But after a season of use with her loaded with fuel, water and all our stuff, 12 is about the best she will do. We mostly cruise around 8 KTS and I averaged 3.5 gal / hr over the season, so I am not unhappy with her overall performance.

 

[OldDan1943]

speed through the water or speed over ground?

 

[garmstro55]

Geeze... how could I forget that..... fixed it, thx.


Yanmar 370, 6LYA STP

Here's what the factory said in 2005

 

[Capt Mike]

MS 400 Speed

speed through the water or speed over ground?

My speed reference is SOG using GPS at slack tide, late in the season so marine growth might be a contributor to resistance thru the water.

 

[jefndeb]

I am not sure I understand the screenshot above...we have a 2006 Mainship 400 with a single Yanmar 6LY2AN-STP 440 HP and we run about 2500 RPM, 8 to 9 knots, it shows 9+ GPH at 2500 RPM?....am I reading that right?

I thought it was more like 3 to 3.5 GPH.....

 

[Arc]

You are not running a 440hp @2500. Rpm @3.5 GPH. More like 1 MPG or less

 

[Jgutten]

I had a Mainship 400 with the same Yanmar 370 hp engine. I couldn't get it above 12 kts. with two aboard at full throttle. I've never seen 15 kts in the boat.