Engine and outdrive advice

[Smoothgred]

Hi all,
A newbie here to the forum and to boating!
Hoping to be on the boat looking back rather than still on the quay dreaming:-)

I'm looking at buying a 30' cruiser type boat and have seen a Maxum 3100se which has the layout that we like.

However she has twin Mercruiser 4.2 D Tronic 250hp engines mated to Bravo 3 XR drives.

Firstly I am trying to estimate fuel consumption at cruising speed which the broker details show as 25kn.

The boat has a dry weight of 5000kgs.

Secondly reading about the Mercathode anti corrosion system on the Bravo 3 drives there is mention of the need for current from the battery to maintain the system.......I am thinking of using a mooring rather than a marina berth and wondered how marine batteries would cope? I haven't found what the current draw is yet.

Any help appreciated.

[mlines]

Trying to find out the Mercathode current can only be by experiment I am afraid. It depends on the condition of the anodes and the salinity of the water and the level of exposed metalwork you have in the water and will vary from place to place and time to time. We have never seen any battery issue attributable to the mercathode on our boat but it has probably never been more that two days in the sea or river on its own without a charge of the batteries. HOWEVER we did have river anodes on once when in salt water and oh boy did it manage to electroplate our props!

Our boat is lighter than yours (2800kgs) and has a V8 petrol engine, however I would have thought you might be able to cruise quite economically with diesels . Our petrol burns 30 litres (6.5 Gallons) an hour at around cruise speeds of 25knots rising to 86litres an hour flat out at 46knots (53mph)

[BruceK]

Welcome to the forum.

Fuel consumption: I would expect about 40 lph cruise speeds with twins.

You can play with these simulators but not sure your engine is in. http://www.boat-fuel-economy.com/outboa ... ion-liters

As for mooring. Get a nice 80 -100W flexible solar panel (one you can walk on) and fix it flush to the deck sunpad where the beach bunnies always perch for the marketing photos. If you are on a mooring it will be the second best investment after buying the boat.

[Smoothgred]

Hi Mlines and BruceK
I appreciate your comments and will look into getting the solar panel if we buy the boat.
Thanks

[Ianfs]

Hi Smoothgred

Welcome to the forum and I wish you luck with buying a boat.

Maxum 3100's seem quite rare in the UK and the one at £62k is way over priced, someone is having a laugh.

Fuel consumption: I would expect about 40 lph cruise speeds with twins.

I would have thought a tad more, but a lot depends upon what speed she starts to plane (at a very very rough guess 15nts) and at what revs she is making (again a very rough guess, 2,500 rpm).

As for the Mercathode, I agree with Martin, a lot depends upon experimentation, anything from 15ma in fresh water to 200ma in sea water. This boat would have house batteries, or at least I would hope it has. These are separate from starter batteries so at least if they run down you can start your boat. However Bruce has given you the answer, get some solar panels.