Practical application of electric auxiliary on Sportfish

[juiceclark]

I have read at least a dozen really great strings on this website about using generator to electric motors for auxiliary power on all kinds of boats. After a pile of reading about the torque, reliability, and expense differences of hydraulic power off the genny and other options, I'm convinced putting a 50+-hp electric motor on each shaft will allow a 50' sportfishing boat to troll along at 8knots and it's the best option.

However, what I haven't seen are practical scenarios how to get the power in the electric motors out to the props. Our sportfish will be about 50' loa with a 17' beam and will run about 50,000 pounds loaded. Likely power options will be twin 700hp C-12 Cats, a single 3412 1150hp Cat...or the like. So if you mount a 50 hp electric motor alongside each shaft...how do you drive it? One product showed a belt-drive...well, with all the torque in a 50hp electric motor that'll be some belt! Moreover, how can the belt be disengaged remotely? It would have to be disengaged or it would drag on the big, primary motors when running...right?! Moreover, you can expect to crawl into the bilge and screw with it everytime for it to work.

The cost advantages of doing this are so great, for a boat that trolls for fish all day but needs to run out to the grounds, that it is well worth the cost of a big genny and the rest of the set-up. But I haven't seen it done anywhere and have no idea of the arrangement. Have you?? The Vetus hydraulic motor would be a simple installation and many gensets come with a port for that purpose. But I haven't seen anything about electric motor application in the bilge of a sportfishing boat.:confused:

Moving from the theoretical to actual application is tricky! Tony

[CTMD]

Build the motor directly into the shaft line. so you end up with:

Prop-Shaft-thrust bearing-Coupling-motor-coupling-clutch-gearbox-engine.

also note that as you can do all your backing on the electrics only you could loose the gearbox if the engines have a suitable RPM.

There is no need to disengage the motors they can free spin without damaging anything or be used as generators will the engines are running (think giant PTO)

[charmc]

Tony,

I can't locate the details right now, but there are hollow shaft assemblies with clutches that will allow a parallel drive motor to connect by chain or belt. The clutch will allow the auxiliary drive to disconnect from the prop shaft when running on main power. Or, as Chris suggests, there are motors that can be driven as generators.

[juiceclark]

Thanks. Mounting the electric motor with the 2.5" or shaft running right through it seemed to me to be the obvious set-up. I guess I just haven't seen it anywhere to examine. The belt drive clutch assembly seems easy enough as well - just having trouble envisioning the automated clutch system.

If anyone has any pics or links I'd love to see them.

[prakashsf]

Tony -

Have a look at the Allison transmission E-drive. This has been used for electric buses but may be suitable for marine as well. It offers e-only, d-only, e+d modes and is complete with a control system. Looks like it can be retrofit. Not sure about marinization needs but it is an infinitely variable transmission with the 2 electric motors for a parallel hybrid application.

Another website Bentley marine carries a similar system as does Vetus Marine.

Have you done an analysis of propeller thrust and power requirements for various speed and house load conditions? I 'd be interested your thoughts. Although some time out, I am tying to design propulsion for a 80ft 100GRT steel trawler with 220KW single mains and a 50-70 kw auxillary system feeding the parallel electric system. The design goal is 1.5 MPG under steady sea conditions.

Prakash

Prakash