Propulsion general questions for heavy use on 30ft power cat.

Motors are in hulls, basic straight shaft setup. All monos here are straight shaft and well over 30 years in water, i'm using one myself. Hauling out for anodes not that big of a deal in return transom is clean. Marine growth is not an issue here. I'm not sure what exactly is leaking from volcano into port, but upper layer is orange most of the time and keeps barnacles away rather well. Oxidized iron probably. This is how it looks from above. There are also no owners of outboards around here that i could talk with or even mechanics that i could get advice. So i'm still torn between two choices.

 

Metals in the water I'd say.

I would want ob first, diesel ib next, electric last.

Electric gonna change too much next 20 years.

 

I sometimes wonder whether a single"longtail" drive might not work on this type of cat. Maybe Richard Woods can give you an opinion on that.

 

That's a lot better view than Kobe harbour that i see daily! Wanna swap...?

If it were me, and the issues you've noted. Just go for long slender (high length-displacement ratio) design with a small outboard on each and supplemented by small sails. Thus when the wind is in the right direction just sail to the site.
And then use the motors when sailing is not an option. Best of both worlds.

Plenty of decent J's outboards available here, as I'm sure you know.

 

While island life can be difficult, i won't change this place for any other. Fishing paradise right beside us that i won't be able to find anywhere else

I sure would love to have boat with purpose made design, use carbon fiber for everything, etc. But i'm on my own now, money situation doesn't allow it Richards design cost me under 1k usd, since i was one of first to buy it, so got a discount. In addition, design consists mostly of straight lines and a bit of slight curves that are easy to do. I did search for ready designs before settling with Richards Jazz 30, but light and long displacement cats just didn't come up. Racing sailboat minus rig only, but again it's not optimized for power and far more complicated to build. I asked before how much custom design could cost, but didn't get even example price. So it's probably way out of my price range.

Back to the question, here i see everyone supports outboards as first choice. More points for outboards. I still need to learn more about maintenance though.

What would be the point of longtail drive on cat over ready available outboards? How is steering from remote controller? Bare engine i see on photos is just too dangerous, need housing.

 

They are a bit of a rough-and-ready 3rd World type of solution, but I am attracted to the idea of single engines for fuel economy, and especially with a prop working in water that has not been dragged along by a hull ahead of it. The fuel consumption can be reduced substantially. But it would be difficult to set up such a drive on a cat with a high tunnel. Just a thought.

 

I'm surprised the hull design would suit inboard or electric. The Skoota 32 has a lot of stuff aft, xtra bulkheads, knees and such. I have a feeling you are underestimating the importance of space to work. The Skoota 32 hull bottom is under 22" wide.

For nearly any service on the inboard diesel; you will be cramped. Electric motor obviously smaller.

Not saying impossible, but not easy.

 

Before buying plans i did ask Richard about possibility of straight shaft electric version, he said it should be possible. Inboard diesel i discarded already, too much trouble even if it could be fitted.

 

The Tesla electric engine is made a bit different. I suspect some of these engineering marvels will make their way to marine service, so perhaps you can plan to change it

 

I believe this is the wrong reason to go electric. You want a fishing boat and you will be fishing and possibly commercially (you mentioned commercial power prices.) The right thing to do, in my opinion is to go with a cost effective outboard. Outboards are easier to replace down the road and more access for maintenance, though of course there are performance problems.

Your use case is actually pretty good for electric, given that you dock every night... but those power rates are "We don't want you using electricity" rates. EG: that electricity is coming from somewhere that is probably not great for the environment or otherwise is very expensive. Thats' your electric provider telling you not to use electric.

Secondly, if you go with outboards and you have an extra mounting bracket you can get an inexpensive electric trolling motor and use electric for some low speed situations where you don't need the full power of the outboard.

Ultimately, electric will be adopted by boats as it is by cars for economic, not environmental reasons. We aren't there yet. A lot of R&D and production development needs to be done... but ultimately electric vehicles will be cheaper. Its the job of Toyota and Nissan and Honda and all them to get use there, not you. Honda will have electric outboards and you can swap yours out then.

If you are bound and determined to go electric, consider a hybrid system. The way submarines work-- get a generator, run that generator at max efficiency, and then your battery bank is just an accumulator. Then you can use an off the shelf Torqueedo or competitive electric outboard. When you need to go really fast you pull from the battery bank... and when you need distance the generator runs and keeps the battery charging and the motor running.