Marex 310 SC to be moored in the South of France - single or twin screws?

[SouthWales]

I am new to all this an am in love with the 310SC as a first boat. Quite a few second hand examples are now offered for sale and am wondering whether I should go for the single or twin Volvo Penta?

Bonus question: how easy is it to retrofit a mains-only HVAC on this boat?

 

[footsoldier]

You stand more chance of getting a response if you post this in the appropriate sub-forum - Motor Boating

 

[john_morris_uk]

You stand more chance of getting a response if you post this in the appropriate sub-forum - Motor Boating

Moved…

 

[jfm]

For med mooring, i would definitely get twin screws. Much easier to nudge/push the stern sideways in either direction, and that's important in med mooring.

Mains only HVAC is a big job and not cheap, but very do-able and a well trodden path. The challenges are finding spaces for the hardware and running the piping and ducting. Also you have lots of choices (or cost/benefit decisions) to make as between split gas, chilled water circulation, selfie units, one compressor or two, inverter driven variable speed compressors or not, and so on. It's easy to say which is best (2 inverter chillers and chilled water circulation) but that's also the most expensive.

 

[SimonD]

I'm not familiar with the Marex 310 but, being Scandinavian, at that size, it might have been designed for a single engine. (The Scandinavians are less paranoid about relying on one engine than us Brits apparently.) Why is that important? I can only give you the example of the Nimbus 320 (cos I have one). This was designed with a single engine but, for the UK market, they made a version with twin engines. This took some space from the second cabin and is a bit of a squeeze in the engine bay. The rudder also had to be divided into two rudders and lose the protection of a skeg. None of this is a criticism, but you should be aware. If manoeuvrability is a concern, get a stern thruster fitted.

 

[ari]

For med mooring, i would definitely get twin screws. Much easier to nudge/push the stern sideways in either direction, and that's important in med mooring.

It's an outdrive boat, so you can direct the stern thrust just by putting the helm down the appropriate way.

 

[greg131187]

Our 310 in the Uk is a single d6 370. It's a great boat and you won't be disappointed! I find the single D6 quite easy to manoeuvre as the steering is light and with electronic throttle you can easily click in and out of gear. Full lock and a quick in and out of gear moves the stern quite far. I think as it's a big single there is a significant shove which makes all the difference. Always wheel before engine. The bowthruster is strong too.

She does top out at 34knots but we cruise at 21 knots almost always as it's the most comfortable.

That being said it is a quite high sided boat for size and it can be blown but as long as you prepare, stay upwind of any obstacles it's fine. Singles vs twin won't change that.

I do notice that with some fowling and in a following sea I have to work the throttle delicately to keep it on boost, I don't know if twins would mitigate this....

Looking at images of the singles vs twins on the Marex the twins do give more room forward of the engines before the fuel tank (4cylinder vs 6) this May give you better options if you wanted to mount a gen or ac. Obviously the single has more room either side.

 

[DavidJ]

Bonus question: how easy is it to retrofit a mains-only HVAC on this boat?

If you are looking to cool only I can’t believe the price of this.
Climma Compact Air Conditioner 9 CO 9000 Btu/h
I DIY fitted one in my S37 and it fits under the saloon settee. The power is adequate for north Spanish Med and mine has electric heating as an extra.
I fitted a water pump which will handle two units but I’ve never needed to buy a second.
By the way I exhaust the water straight out the bottom so as not to annoy the neighbours.

 

[Elessar]

For med mooring, i would definitely get twin screws. Much easier to nudge/push the stern sideways in either direction, and that's important in med mooring.

Mains only HVAC is a big job and not cheap, but very do-able and a well trodden path. The challenges are finding spaces for the hardware and running the piping and ducting. Also you have lots of choices (or cost/benefit decisions) to make as between split gas, chilled water circulation, selfie units, one compressor or two, inverter driven variable speed compressors or not, and so on. It's easy to say which is best (2 inverter chillers and chilled water circulation) but that's also the most expensive.

disagree - single at this size all day long for me.

Cost (both servicing and fuel) , accessibility (=reliability), and in a shaft boat just fit a sternthruster. Out drive and single/twin makes little difference to manoeuvrability.

 

[jfm]

disagree - single at this size all day long for me.

Cost (both servicing and fuel) , accessibility (=reliability), and in a shaft boat just fit a sternthruster. Out drive and single/twin makes little difference to manoeuvrability.

All fair points Elessar. Problem with these types of question is that we as readers don't know the OP's priorities. One could answer the question thinking about what is best to operate with, or what is cheapest, or some blend that takes account of cost/benefit, but each person's view of cost/benefit differs.

All that said, with a fast boat that has coarse props, there is no plausible stern thruster that comes close to pushing the stern as hard sideways as the propellers do when you split-sticks it. ( I appreciate that isn't the case with duo-prop outdrives and perhaps this boat has those - I didnt research what a Marex is)

So I stand by my original answer and I walk my own talk but I don't expect everyone or anyone to agree

 

[Elessar]

All fair points Elessar. Problem with these types of question is that we as readers don't know the OP's priorities. One could answer the question thinking about what is best to operate with, or what is cheapest, or some blend that takes account of cost/benefit, but each person's view of cost/benefit differs.

All that said, with a fast boat that has coarse props, there is no plausible stern thruster that comes close to pushing the stern as hard sideways as the propellers do when you split-sticks it. ( I appreciate that isn't the case with duo-prop outdrives and perhaps this boat has those - I didnt research what a Marex is)

So I stand by my original answer and I walk my own talk but I don't expect everyone or anyone to agree

All good points and on larger boats I’d agree without reservation.

Trump argument for me is access on a boat this size. And the engine(s) will be 4 litre max and high revving so it won’t have the course prop bite benefit either.