Model:  1971 Alwest 370

Hull ID:  37071156

Owner:  David Pearson and Bonnie Lindsay

Home Port:  Portland, Ontario

Power:  Volvo Penta 4.3GXi with SX legs


This is our Alwest 370.  The photograph was taken at Newboro lock on the Rideau Canal. The boat is a bit of a work in progress.  As a matter of fact, “Work-in-Progress” was one of the names we both liked for the boat.  I must confess that my wife and I disagree over what to call the boat.  The instant I first saw the boat the name “Buster” popped into my head.  Unfortunately, not many people like the name, so we have never officially named the boat.


The original power in this boat was a pair of Volvo-Penta 170HP 6 cylinder in-line engines linked to Volvo-Penta out-drives.  The manufacturer’s claim is that this power system would push the boat along at a top speed of 25MPH.  Well, we purchased the boat with one dead engine with the intent that we would re-power.  After much analysis, we selected the Volvo-Penta 225HP V-6 engines with SX legs.  These engines are slightly heavier than the originals, but with the generator removed, it was about back to normal.  With this power system, the boat tops out at darn near 40MPH (I have seen 39 on the GPS, and that was with the legs full down) and it cruises beautifully at around 25.

It took a little while to sort out the props.  The Volvo pre-sales guys decided that it needed a higher ratio gear set to allow the engines to spin up.  The initial prop selection was a 14 x 19.  These props let the engines over-rev, so we eventually worked up to a 14.25 x 23.  These were a good size in terms of engine RPM, but the boat had trouble getting up on plane as the props are fairly close to the water surface and would blow-out quite easily with resultant over-revving of an engine.  It took a very precise hand on the throttle to control coming up on plane.  The next step was to look for more blade area.  I eventually settled on Mercruiser 15.25 x 22 4-bladed stainless props.  These are still not perfect as we get a little bit of cavitation whine if we are loafing along on a low speed plane.

Buster at cruise speed (click on picture for larger image)

Buster at wide-open throttle (click on picture for larger image)

Electrical system

I have my own ideas about what makes a good cruising electrical system.  What I did not want was any sort of reliance on a generator.  To that end, I removed the generator that came with the boat and dropped in 4 Trojan golf-cart batteries and a 1750W inverter.  The batteries are 6V, 225AH lead-acid types.  They each weigh around 65lb.  I removed the 120V stove, the window air-conditioner (yep, a Home Depot special) and the evaporative type fridge.  Interesting to note that the fridge could run on 12V, but it drew 10 amps while running.  We installed a low-power 12V/120V fridge (average draw on 12V is 1.5A) and a Force-10 propane cook-top.  With this setup we can live away from shore power for around 5 days without worrying about power.  If we go into a low-power consumption mode, the batteries should be able to last around 10 days keeping the fridge running.

Battery wiring

The batteries are configured in 3 banks.  There are 2 banks of Trojan golf-cart batteries and 1 cheapie starter battery.  I normally run the golf-cart batteries in parallel to provide 450AH to the house circuits and run them off the starboard alternator.  The port engine only gets the starter battery.  However, I have the battery switches set up so I can split the golf-cart banks apart and move one set over to the port engine for charging.  This allows me to double the charge current if we have really drawn the batteries down from a lengthy stay or use of lots of power (eg power tools, lighting, computer, etc.).  The batteries are wired through to a breaker panel in the aft of the boat with 2ga wire.  There is a separate run of 4ga wire to the main distribution panel in the pilot-house.  The high-power stuff is wired to the aft panel to take advantage of the heavy wire.   The drawing below is the schematic for this setup.

One of the sweet parts about using the Trojan golf-cart batteries is that Blue-Sea Systems makes a nice battery box designed specifically to hold 2 of them.

Inverter setup

The inverter is an inexpensive 1750W unit from Canadian Tire.  It puts out 120V AC with a modified sine-wave.  This means that we cannot run anything delicate from it.  However, we do not have anything delicate that we want to run.  We want to run a vacuum cleaner that draws 1100 watts and maybe a microwave that draws about the same, but not at the same time.  One of the nice things about modified sine-wave inverters is that they tend to be low current draw when there is nothing drawing AC.  The quiescent current of the Canadian Tire unit is 0.4A.   I looked at one Sine Wave inverter that drew 5A with nothing drawing on the AC side.  It had a smart system to shut off the inverter circuitry and “hunt” for a load reducing its 12V draw to around 0.3A, so my low-current argument is pretty weak, but it allowed me to save a pile of cash.

My home-brew chart-plotter

See how I built a chart plotter from a Police car computer

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