CONTINUOUSWAVE

I own a [c.2006] 235 CONQUEST. I do not believe there is anyway to install a 9.9-HP gasoline auxiliary engine for use in emergencies (as I had installed on a prior boat).

Q1: is using a small electric motor which would be stowed and only deployed when necessary a practical solution?

[Moved to THE GAM forum for discussion--Moderator]

A typical emergency situation might be your boat battery was unable to start your main propulsion engine.

Q2: in that situation (no battery power available), how would you power an electric motor for propulsion?

Q3: how many hours of operation would you expect the electric motor to be able to operate with enough thrust to propel a 235 CONQUEST at a reasonable speed, and how many stored Ampere-hour of energy do you plan to have on hand at all times?

Q4: what boat speed do you want the small electric motor to be able to produce with the 235 CONQUEST?

In a typical emergency situation, the sea state may be rough, winds will be high, and wind waves will be rapidly growing.

Q5: what level of thrust from a small electric motor will be necessary to propel a 235 CONQUEST into large headseas and strong headwinds that might exist in an emergency situation?

Thanks for the reply, great questions - I probably don't have all the answers for. My concern is crossing 15 to 20 miles in the Great Lakes, some places rather remote. If I had a small back up motor - even traveling 4 - 5 mph would keep me moving closer to shore - or more likely to a tow. I have 2 batteries on board, and could consider a separate one for such trips. I would only have the small motor on board for long trips, not boating around my home (example - Holland MI to Grand Haven MI). And your point of wind and waves certainly enters into the equation. I believe the only point to mount would be the swim platform (rated for 300 pounds).

Simple solution is to have confidence in the 2006 Verado 225 that is well maintained and keep my towing insurance in force. But I do like to ask the question - "What if..."

Mounting the electric propulsion motor on the swim platform sounds like something that would be very dangerous to undertake in any conditions except very calm seas and minimal wind. My inference is you would need to pre-install the electric motor on the swim platform before you embarked on a long open water journey.

I don't have any good advice about how powerful the electric propulsion motor should be, but for a 235 CONQUEST I would expect that a conventional outboard of about 8-HP would be a good fit.

I think some manufacturers of electric propulsion engines might be able to suggest what electrical power would produce the equivalent thrust as an 8-HP outboard engine with a well-chosen propeller.

There is also the problem of steering. I doubt that operating a tiller on an electric propulsion motor mounted to the swim platform is going to be really effective. The best set up for an auxiliary propulsion motor is to have it steered by a link to the main propulsion engine.

For a good example see the nice installation of an 8-HP outboard with a steering link to a 225-HP outboard shown at:

Mounting a Yamaha T8 Four-Stroke Auxiliary
On a 1992 OUTRAGE 22 with Evinrude 225-HP Main Engine
https://continuouswave.com/whaler/refer ... icker.html

Another problem not mentioned yet is control of the engine speed and transmission. If the throttle is a twist-throttle on the engine tiller, that will also be awkward to control.

Again, thanks for the information - and for pointing out several problems that would need to be worked out.

I probably will boat without the backup motor. I have traveled long stretches in the great lakes, and depended only upon the one motor.

Thank you.

By the way, I also have a single engine boat (1990 REVENGE 22 Walk-Through Whaler Drive with 2010 E-TEC 225) that I have used on the open waters of the Great Lakes for many year, without having an auxiliary engine. We have made some long open water crossing, especially on Lake Superior, but often we have done this in the company of another boat or two. Having companion boats when far from shore on the Great Lakes is reassuring. Our longest solo jump was about 75-miles from Washington Harbor on Isle Royale to Copper Harbor, running for several hours out of sight of all land and alone.

It has been our good fortune to not have any serious problems with that boat and engine on those trips. Actually, the biggest source of problems has been the towing vehicles and the boat trailer.

Buying clean and non-ethanol gasoline fuel, using premium oil, keeping two batteries at full charge, and having periodic maintenance done professionally has certainly helped keep the engine operating normally.

A little back-of-the-napkin math to check feasibility here...

Let's go with Jim's estimate of 8 HP on a continuous basis. That works out to about 6kW. We'll make the simplifying assumption that the electric motor and everything else in the system is 100% efficient so that we need 6 kW of electrical power to generate our propulsive power. We'll further assume that it's a 24 VDC motor, so 6 kW at 24 V is 250 A of current.

If we look at some nice batteries to power this, we might consider the Dakota Lithium 12 V 135 Ah battery. It's not cheap at about $1000 but it's nice quality.

We'll need 2 of these batteries in series to get 24 V, but the overall capacity is still 135 Ah. At 250 A current, we'll get just over 30 minutes of runtime from the batteries. That'll get us a couple miles, which is not a lot of bang for our buck, and we haven't bought the motor yet either. More batteries will get us more range, with the obvious size/weight/cost impacts.

By the way, for 250 A we'll need something like 500 MCM copper wire to give us a 20% safety margin. That wire is about 1" diameter, 1.6 lb/ft, and $16/ft. That's a lot of heavy, expensive copper. We could cut down the wire size by going with a higher voltage, but then we need more batteries.

Could you do it? Sure, but you'll end up with a heavy, slow electric boat with a 225 HP gas auxiliary engine.

Jim's comments - "Buying clean and non-ethanol gasoline fuel, using premium oil, keeping two batteries at full charge, and having periodic maintenance done professionally has certainly helped keep the engine operating normally." I certainly do these things. I almost always boat by myself. Hope to go from Mac City to the north channel - longest run would be 60 - 70 miles. I have done whitefish point to Mac - long but close to shore for the most part.

GoldenDaze comments - interesting, a reality check - no electric motor for me.

Thanks to both of you...

I do not believe there is anyway to install a 9.9-HP gasoline auxiliary engine for use in emergencies (as I had installed on a prior boat).

What is it about the design of your 235 Conquest that makes you think there's no way to install a gasoline auxiliary motor?

Have you considered using a bracket?

Is there something about the design of the transom that makes using an auxiliary motor bracket infeasible?

Is your boat a model year 2006 [to match the VERADO engine]?

John--I believe the 235 CONQUEST has a narrow notched transom that can only accommodate a single outboard engine. Also there are pockets molded into the transom for trim tabs, and these could hinder installation of a mounting bracket for an auxiliary gasoline outboard engines. Finally, there is a swim ladder and small platform mounted on the starboard side of the transom, further hindering mounting of an outboard auxiliary engine.

This link to a drawing for the 2006 235 CONQUEST shows these details:

https://www.bostonwhaler.com/content/dam/boston-whaler/technical/resources/235-Conquest-Final-Assembly-and-Parts-List-2006.pdf

Also, I think there was an error (typo) in expressing the model year of the 235 CONQUEST in the initial post. The first model year of the 235 CONQUEST was 2006, so your comment regarding matching the 2006 VERADO engine is likely correct. I emended the initial post to indicate the boat was a c.2006 model on that basis. Thanks for pointing out the conflict.