Builder trials on A0001 and reassessment

Les Lampman

A0001 (production hull #1) went in the water early this morning for her builder's trials. I learned a lot and it changes some of the concepts I had about the boat.

As many know this boat has been powered with a Honda BF115D, which is really a detuned BF135/150. It's a large block for a 115-hp engine and because of that it only has about 2 ft-lbs of torque less than the BF150. What's really neat though is that peak torque comes in at a fairly low 3,500 rpm, and that turns out to be the cat's meow for this hull.

I was confident based on Dave's prototype M215 that it would handle the weight of the Honda BF115D (the result of it being the same engine as the BF135/150) and the kicker too. Of course, that was "paper" confidence since no M215 existed at that point equipped like that. Well, it's paper confidence no more; with full fuel, full water, the BF115D and the Tohatsu 9.8 kicker the boat sits dead level in the water and handles beautifully. In this configuration with two folks aboard the M215 planes out just shy of 9 knots.

The other thing is that I underestimated the speed range of the hull. With the E-TEC 90 on Dave's M215 I typically cruised the boat about 18 to 20 knots but I've now found out that was mostly due to noise and the sound of the engine. With the now quieter boat (and engine) with the BF115 the Marinaut cruises comfortably at 25 knots. And that's not in flat water, I ran that speed though some pretty good tide rip chop and the hull doesn't pound and slap. With the BF115 cruising at 20 knots (23 mph) is pretty effortless at 3500 rpm (fuel consumption at that rpm is 4.6 gph).

So, my take is with a 90-hp engine the M215 feels closer to the CD22 (still a little faster at cruise if wanted). With a 115-hp engine it feels very close to an Arima 21 Hardtop with a 150-hp engine. Truly either engine works great, it's just going to be about either the cruise speed you want or the weight you want to haul.

I've got the NMEA 2000 bus connected to the BF115D and to the Raymarine C90W which gives rpm, fuel burn, voltage, engine coolant temp, engine hours, etc right from the engine's ECU to the C90W display. The following numbers come from the engine for rpm and fuel burn and from the GPS (speed over ground) for the speed (and I tried to average by running multiple directions).

Here's the chart I generated this morning (keep in mind this is a M215 with full fuel and full water but not a lot of other gear) running an aluminum Solas (Honda OEM) 3-bladed 17" prop.

3000 rpm..........3.4 gph..........15.4 kts
3500 rpm..........4.6 gph..........20.3 kts
4000 rpm..........6.2 gph..........25 kts
4500 rpm..........7.8 gph..........28 kts
5000 rpm..........10.2 gph.........31 kts
5400 rpm..........10.5 gph.........33 kts

The BF115D makes maximum horsepower at 5,250 rpm so I'm pretty happy with where the 3 x 17 prop ended up. If the rpm drops much when fully loaded (gear and people) I'd be inclined to try a 4 x 15 prop. A 3 x 15 would work but I think it may take the rpm up higher than needed; not higher than redline (6,000 rpm) but high enough that you'd lose the benefit of the down low torque on the BF115D.

Another speed I found I really liked this morning was running 3200 rpm at 18 kts with a fuel burn of 3.5 gph. Running 3400 rpm at almost 19 kts (like 18.8 to 18.9) with a fuel burn of 4 gph was also a nice speed.

All-in-all I consider the M215 to be what I would call a "20 knot cruise boat" and with a 115-hp engine a bit higher speeds are still quite comfortable.

I still found that the boat tracks like an arrow. It will run for quite some time hands-off and not wander around. I run with the autopilot doing the steering duties about 90% of the time but having a boat that tracks like the M215 means the autopilot is working easier.

To say I'm pleased would be an understatement. Of course since I build the things I'm biased but I'm also honest enough to "tell it like it is" regardless of whether it helps or hurts me. Folks that are going to spend this much money (any amount really) are owed the truth.

I had the hard bulkhead in this morning but I have to tell you this boat is superb with the aft bulkhead out. What an open feeling that gives the boat. Of course in the winter (in the PNW) I'd have it in but I can really see removing it in the spring and leaving the cabin open to the cockpit (with a Bimini or camper canvas is the best).

In being aboard the M215 with the aft bulkhead removed and the full camper canvas up I thought "what a great family boat". That's not what I was thinking before that. It seemed like a great couple's boat. But with the aft bulkhead removed and the camper canvas up there is so much inside space, plenty for 5 or 6 people to move around and be comfortable. Plenty for a couple with a couple of kids or so to camp aboard; mom and dad at one end and the kids in the other...still visible and easy to keep track of and close at hand if needed. There's comfortable sleeping on the v-berth and a really comfortable sleeping space in the cockpit with something like an air mattress in place.

Thanks everyone for being here and being part of the process (and the joy).

All the best...

Aurelia · Posted: Wed Sep 21, 2011 4:47 pm Post subject:

Great to hear it went well Les! Now slap the lighter tohatsu 115 on there and compare! if it was that easy....

oldgrowth · Posted: Sun Sep 25, 2011 1:34 am Post subject:

I used Les’s data in the above post to create the following chart for the Marinaut 215 with a Honda 115hp engine.
This is with full fuel and water plus two people on board.
I have added several columns to indicate MPH, MPG and NPG.
GPH = gallons per hour
KPH = knots per hour
NPG = nautical miles per gallon
MPH = miles per hour
MPG = miles per gallon

Dave

www.marinautboats.com

Les Lampman · Posted: Sun Sep 25, 2011 1:15 pm Post subject:

Thanks for the table and graph, they look great.

We'll see how this plays out over time when there's more data available at different weights and in different sea conditions. For now I'm quite pleased with the package.

The fuel burn rate is nice but even better for me is the smooth quiet engine and how nicely it reacts to throttle adjustments. Very smooth, very tractable; makes it easy to work through the slop.

Les

nymariner · Posted: Sat Oct 08, 2011 8:53 pm Post subject: 5-15 knts fuel usage

Would you please post the fuel usage readings for the lower speeds? Thanks

mailbox101 · Posted: Sun Oct 09, 2011 4:34 am Post subject:

Captains Cat · Posted: Sun Oct 09, 2011 9:41 am Post subject:

Yes, it's redundant. I think he meant NMPH, Nautical Miles Per Hour, not Knots Per Hour.

A knot is a nautical mile per hour.

Brought to you by your Department of Redundancy Department

oldgrowth · Posted: Sun Oct 09, 2011 11:38 am Post subject:

Knots per Hour and Miles per Hour is the distance traveled in one hour.
A mile is 5280 feet
A knot is 6,076 feet 1.39 inches
To convert Knots per Hour to Miles per Hour you multiply the Knots per Hour by 1.1508
To convert Miles per Hour to Knots per Hour you multiply the Miles per Hour by 0.869

Dave

www.marinautboats.com

rogerbum · Posted: Sun Oct 09, 2011 11:44 am Post subject:

thataway · Posted: Sun Oct 09, 2011 5:37 pm Post subject:

Sometimes it pays to distinguish: Nauctical miles per hour vs statute miles per hour. In many parts of the ICW's of the East and Gulf, the distances are in statute miles--and thus people speak of speeds of miles per hour (statute)--where as other places rather than say Knots, they might say nautical miles per hour for clarification....Probably this distinction is more valuable for a new boater.

Les Lampman · Posted: Wed Oct 12, 2011 12:40 pm Post subject: Re: 5-15 knts fuel usage

Les Lampman · Posted: Fri Oct 14, 2011 6:59 pm Post subject: Re: 5-15 knts fuel usage

Dene · Posted: Sat Oct 15, 2011 7:33 pm Post subject:

Les,

You described it as a family boat. Can mom and pop sleep comfortably in the V-berth? My understanding is that it's 48 inches wide. If so, kinda narrow isn't for two, normal sized people.

-Greg

Captains Cat · Posted: Sat Oct 15, 2011 8:45 pm Post subject:

Not sure where you got your "understanding" but the typical v berth, and the Marinaut isn't much different in that area than a CD22 (except for the insulation) tapers from just a little (play footsie with each other) at the bow to just about the full beam of the boat where your head is. At that part, you are separated from your crewmate by the porta pottie space which can be covered up with a cushion (think it's that way on the Marinaut too). That's probably 6+feet wide where your head goes, a lot greater than 48"!
Take a look at the LINE DRAWINGS

Charlie

C-Nile · Posted: Sun Oct 16, 2011 2:02 am Post subject:

Actually Charlie, the Marinaut Berth is not similar to the CD 22. The CD 22 has a closed-in bulkhead which compels people to sleep in a feet-forward position. Some CD 22 users have cut out their bulkheads, which creates a much more open berth. Those users have a closer looking berth to the Marinaut. My wife and I sleep with our heads toward the bow, and we are extremely comfortable, having done so for 19 straight nights! The berth really has much more space than the line drawings would otherwise indicate. Please see my folder showing our berth arrangement.

[img] http://www.c-brats.com/modules.php?set_albumName=album1497&op=modload&name=gallery&file=index&include=view_album.php [/img]