Inboard /outboard vs 2 outboards for 34' catamaran

[sailor4life7777]

Hey guys just wanted to get everyone's opinion, what would you prefer and why on a 34' catamaran? One inboard diesel with alternator and a diesel outboard in the other hull vs two diesel outboards and a generator? There would be weight imbalance issues with the inboard/outboard setup but that can be balanced by putting heavier objects in the lighter hill until its completely balanced. I like the fuel efficiency and ability to make hot water with the inboard diesel. What would you guys prefer and why?

Thank you so much for any input in the matter!

[Bunji]

Originally Posted by sailor4life7777

Hey guys just wanted to get everyone's opinion, what would you prefer and why on a 34' catamaran? One inboard diesel with alternator and a diesel outboard in the other hull vs two diesel outboards and a generator? There would be weight imbalance issues with the inboard/outboard setup but that can be balanced by putting heavier objects in the lighter hill until its completely balanced. I like the fuel efficiency and ability to make hot water with the inboard diesel. What would you guys prefer and why?

Thank you so much for any input in the matter!

2 x 9.9 hp yamaha high thrust (petrol).
Lightweight, cheap, simple, 3 to 1 gearbox ratio, 12 inch prop, 25 inch leg
5 litres per hour combined
Push you along at 6 to 7 knots (hull speed)

[Tupaia]

A diesel out board will be too heavy too far aft and too much power for a 34ft cat.
2 x 10 or 12hp diesels if you really must have diesel or 2 x 9.9 Yamahas as Bunji suggests is a much better option.


What design is the cat?

[Tin Tin]

What size diesel outboard did you have in mind?

[Adelie]

Welcome.

I would suggest updating your profile with your general location and your boat make & model or “Looking” in the "Boat" category. This info shows up under your UserName in every post in the web view. Many questions are boat and/or location dependent and having these tidbits under your UserName saves answering those questions repeatedly. If you need help setting up your profile then click on this link: https://www.cruisersforum.com/forums...ml#post3308797

If you need further help let me know, I would be happy to.

Where are you? If you are trying to source diesel outboards in the US I don’t think it can be done due to EPA issues with import of new motors unless you pick up an old Yanmar that’s already here.

[valhalla360]

Originally Posted by sailor4life7777

Hey guys just wanted to get everyone's opinion, what would you prefer and why on a 34' catamaran? One inboard diesel with alternator and a diesel outboard in the other hull vs two diesel outboards and a generator? There would be weight imbalance issues with the inboard/outboard setup but that can be balanced by putting heavier objects in the lighter hill until its completely balanced. I like the fuel efficiency and ability to make hot water with the inboard diesel. What would you guys prefer and why?

Thank you so much for any input in the matter!

On a 34ft cat, my preference (and experience) is a single centered 25hp outboard. The outboard tied into the steering to provide directional thrust. Twin engine is really not needed at that size. It just takes up space and adds weight.

In theory a diesel outboard would be nice for efficiency but unfortunately, diesel outboards aren't available in the USA. Probably the bigger issue is even internationally, they are oddball items, so maintenance and repair would likely be more difficult. Gas outboards are everywhere, so there will be people with knowledge and parts available.

For 12v power generation, use solar. If you need more power such as to run an air/con unit, get a generator. About the only advantage of an inboard over outboard is the ability to generate hot water but that only applies if you are motoring for significant distances that day. On non-motoring days, you aren't going to run the inboard just to heat up water. Get a properly installed propane hot water heater (or if big enough solar array, you might be able to heat off the excess electrical generation).

[ausnp84]

Originally Posted by sailor4life7777

Hey guys just wanted to get everyone's opinion, what would you prefer and why on a 34' catamaran? One inboard diesel with alternator and a diesel outboard in the other hull vs two diesel outboards and a generator? There would be weight imbalance issues with the inboard/outboard setup but that can be balanced by putting heavier objects in the lighter hill until its completely balanced. I like the fuel efficiency and ability to make hot water with the inboard diesel. What would you guys prefer and why?

Thank you so much for any input in the matter!

We have a 30ft cat with a single outboard / bow thruster and have to say, it all works pretty well together. The outboard is easy to maintain and doesn’t stink up the inside of the boat, the bow thruster allows me to turn in a pretty tight space, and all our elec is taken care of by AGMs and 520W of solar.

My last boat was a 42ft cat with twin 40hp diesels and I’d take the new setup any day. Tbh the only thing I’d want is a second outboard as a backup, but otherwise this setup keeps us going at 6-7kts (flat water) and cuts our fuel on board to petrol and propane (rather than needing diesel as well).

N