Monday 18 September 2017


This is the first time we've been using the new tachometer in the wild, and getting used to it is an interesting experience.

It's nice that the engine hours counter works – it was a classic complaint about the old model that it failed fairly quickly. Of course, it's early days…! It's a little different in that the calibrations correspond to 100 rpm – on the old one they corresponded to 200 rpm, so I sometimes have to think twice.

But the main difference is that I found, during the installation process, that the old one had clearly been calibrated wrong, so that it significantly under-read the engine speed. I'm now getting used to a new set of "standard" readings for different situations. Engine speed for going past moored boats is now showing as 1000 rpm, whereas it used to be about 800. That takes some acclimatisation, though my ears tell me everything is fine. Normal cruising speed is now nearer 1500 than 1200, and top canal speed on a stretch where you can do it is up around 1700 rpm.

You get used to this, and you keep listening and you keep an eye on other things, like whether you're producing a wash. But in between times, especially if (a) there's nothing riveting to look at, and (b) you have a mind that works like mine, you start calculating how many amps the alternators are putting into the batteries, given these revised engine speeds. Since the time when I began to think seriously about Erin Mae's electrics, I've had a chart of alternator speed versus current imprinted in some part of my brain, ready to be called up and interrogated. So now I have fun thinking about how many electrons are getting stored away, under the new regime. It's a very satisfying procedure – not just the maths but the fact that they're doing much better than I used to think they were. Apologies to those readers who either don't have a clue what I'm talking about, or think it just shows what a very sad case I am.

There are times when speed is no mere theoretical consideration. As we left our Fazeley mooring this morning, I decided to reverse the couple of hundred yards to the bridge at the junction. I saw a boat coming about a quarter of a mile away, but thought I'd have plenty of time to get to the junction without interfering with his progress. How wrong I was! In the first place, he was coming a lot quicker than it had seemed, and didn't appear inclined to slow down for moored boats. In the second place, the shallowness of the canal (I think) kept causing Erin Mae to get off line, far more than she normally does when reversing. So I had to make regular corrections, for which you have to go briefly into forward gear, which slows you down. After about 50 yards he'd caught me up and decided he didn't want to wait. He rammed Erin Mae's bows to push them out of his way, which left me with no choice but to pull across and let him by. He obviously felt offended by what I was trying to do and asked me a few rhetorical questions as he came by. I chose to apply the principle of "a soft answer turns away wrath" and said I was saying nothing (for the philosophers among you, that's a self-stultifying statement!). So, no harm done, but I must confess some relief when he went the other way from ourselves at the junction!

It's one of those occasions when you're not sure about the effect of having a BCF sticker in Erin Mae's window!


  1. Martin - does the rev counter reading impact the altI assumed that the initial output was defined by the speed of the pulley and the rev counter was for info only?

    1. I'm not sure which bit of the post you're referring to, Andy. I certainly didn't mean to imply that there was feedback from the tacho to the alternator. There's a setting you change on the tacho depending on how many alternator impulses it's going to receive per engine rev, and the old tacho had been set up wrong. Does this answer your point?