Mainship 390 - single vs twins - speeds

[Cdeschene0001]

Hi Craig here,
New to the forum and looking at some Mainship 390's. Trying to figure out the manufacturer history of these boats and obtain some performance data.

Can anyone provide real world numbers on obtainable cruising speeds vs WOT and fuel gph? Online I have read that the single 370 cruises at 8-9 some say 10 and the info on the twin 230's is all over the place from cruise at 10 - 14 wide open throttle 17 - 21?

1) Looking for Yanmar rated cruise speed on the 390 configurations and WOT speed.

2) I read that due to engine noise some will choose to cruise lower than what they can actually cruise at.
Is noise an issue?

3) Any info on the 390 as a rebadged 35 with a molded swim platform?

4) Then there is the 34, any major difference other than length?

Ty

 

[Bacchus]

Welcome aboard TF. Lots of current & past MS owners here so will predict you get some useful info.
Don't know much detail about 390s but my 2008 34HT single Yan 6LYA cruise well at ~1700 RPM and 8.5 MPH or 2700 - 2800 RPM and 13-14 MPH, WOT about 20 MPH depending on passengers, water, fuel aboard. In between is not linear or comfortable... just pushing lots of water. Slower likely a little better but not in my nature.
I found the published 34T/HT data fairly close.
I figure avg 2.4-2.5 MPG w 75% slow cruise & 25% faster cruise. It's held over several years & a few 1,000 miles.
I deal in statute (vs nautical) as we are on Great Lakes & inland lakes, canals, etc and charts & guides primarily statuate mi.

 

[Cdeschene0001]

Welcome aboard TF. Lots of current & past MS owners here so will predict you get some useful info.
Don't know much detail about 390s but my 2008 34HT single Yan 6LYA cruise well at ~1700 RPM and 8.5 MPH or 2700 - 2800 RPM and 13-14 MPH, WOT about 20 MPH depending on passengers, water, fuel aboard. In between is not linear or comfortable... just pushing lots of water. Slower likely a little better but not in my nature.
I found the published 34T/HT data fairly close.
I figure avg 2.4-2.5 MPG w 75% slow cruise & 25% faster cruise. It's held over several years & a few 1,000 miles.
I deal in statute (vs nautical) as we are on Great Lakes & inland lakes, canals, etc and charts & guides primarily statuate mi.

Great info on the Yanmar performance figures. I have had a hard time finding actual real world numbers.
Thank you Bacchus!

 

[Comodave]

Welcome aboard. IMO the main difference between the single and twins would be access room to service the engine(s). The 35 with the added swim platform had some issues with the platform section filling with water. They reworked a lot of them by removing the foam in the swim platform and maybe putting a pump in there. I believe the way to check if it has been done is access hatches in the top of the platform. Good luck with the search.

 

[mncruiser]

I’ve got a 2001 390, single Yanmar 6LP-STE (300hp) The happy speed is about 8.5kts. 9.2-9.5 is high cruise, but that extra knot costs you a lot. I don’t recall the exact readings from my floscan, but the extra knot almost doubled consumption. Top end for me is about 11.5 kts, but it is a violent loud speed, and you are pushing a wall of water.

Early 2000’ish reviews showed my boat at planing speed, but I’ll say NEVER for a real used boat loaded with stuff.

Personally I love the access to everything with the single. If I had twins it would be a lot more difficult.

Stick with the Yanmars or Cats in my opinion. You will find Volvos and they are usually quite cheaper, but look up cost and availability of parts and you will know why.

 

[mncruiser]

Also, the 350 and 390 are the same hull if I remember correctly. All marketing and badging. I thought both had the same swim platform but could be wrong.

 

[Phyrcooler]

Mine had the twin Yanmar 240 hp. Economical long distance at 7 kts. I fast cruised at 11 - 12 kts and about 1 NMPG. That was about the slowest planing speed without pushing too much water. Top speed varied with wind/sea state, but was consistently 16+ kts. Fastest I saw was 18 kts. on a calm, flat day with a clean bottom.

Unless you’re running long distances without access to Sea Tow, I would recommend a single. Mine did the Baja Ha Ha several times (off-shore Mexico). However, as previously noted, the twins make for a frustratingly cramped engine room and difficulty in accessing any outboard-side components. (To say nothing of all the other inaccessible stuff that Mainship made no allowance for repair access! But that’s a different story.)

Good luck on your search.

 

[Cold Duck]

Yup, the 350 and 390 are essentially the same boat with some minor interior cabinet differences. Same molds for everything. Friend of mine has the 390 with the Yanmar, mine is a 350 with the Cat. We end up cruising about the same speeds but different rpm. 7-9kts is happy, 1600-2000 rpm for my Cat. When bought I delivered from Santa Barbara to Sacramento Delta at mostly 2000 rpm for 9 kts. In the Delta we not in a hurry so 16-1800 rpm gets us there smelling the roses along the way. Single Cat gives me about 2+ kmpg. A single does have low speed manuvering issues, have to use the thruster in close quarters but you get use to the small rudder command at low speeds and it becomes a non issue. Love the boat.

 

[Cold Duck]

Oh, I started a thread "Cruise speed ms350/390s" that you might want to look at as comments of various MS 350/390 cruise speeds and engine configurations

 

[Nomad Willy]

Are the twins overpowered?

 

[rslifkin]

Are the twins overpowered?

For the MS 350/390, I'd say the twins are well powered, the singles are underpowered. The hull is capable of planing, but the single doesn't have the power to actually get it on plane (but is overpowered for running below hull speed), so the best you can do is plow along a bit above hull speed if you want to go faster. The twins have enough power to give a good planing fast cruise.