loss of rpm - Page 4

Matt · 20-05-2006, 09:23 PM

Starter solenoids, £2 new from yer next boat jumble!

scottyboy · 20-05-2006, 09:43 PM

You can also check the output from the switchboxes to the coils - but you do need a DVA adaptor for this. I vaguely remember jw posting a circuit of how to make one once.

I would like to know how to make a DVA meter! There quite hard to get hold of! Been after one for ages!

Dan · 20-05-2006, 09:43 PM

Thanks all. Matt, if it was the stator that was gone would I be able to rev it past 2500 when in neutral or would it just not go beyond 25500 at all time?
Thanks

JamesM · 20-05-2006, 10:04 PM

Quote:

Originally posted by Matt
If it's the stator, then it'll be either the high or low speed stator.
The high speed stator cuts in at, I think about 2500 rpm. So if you can't get it over 2500 rpm, that's a good indicator of it being the stator. You can also put an AC voltemeter on the stator outputs and compare left & right, high and low speed readings. You'll likely find one particulary low compared to the others.

I think the rectifier stuff is bollocks, it's a different winding on the stator, and you can quite happily run the motor without the rectifier even installed. The only "risk"is if the rectifier fails and short circuits it can fry the stator, but that's rarer, usually it just swithes off, permenantly

As I said before I didn't know there were low and high speed coils. How are they switched in and out?

Yeah don't recon its the rectifier as the tach feed comes from there and rectifier faults are normally seen as a dodgy tach and/or battery not charging. Motor still runs fine, untill the battery goes flat that is.

RossM · 20-05-2006, 10:06 PM

JBD U HAVE JUST POSTED UR 2000'TH POST

jw. · 20-05-2006, 10:09 PM

Quote:

Originally posted by scottyboy
I vaguely remember jw posting a circuit of how to make one once.

Aye I did but it was a long time ago. It was a capacitor, resistor and a diode. I'll put me mind to it again. It was for checking the output from the high and low speed stator coils. From memory, they should be about 300v.

JamesM · 20-05-2006, 10:13 PM

where does the 300V (or whatever it is) stator output get stepped down?

JamesM · 20-05-2006, 10:17 PM

Quote:

Originally posted by jw.
Aye I did but it was a long time ago. It was a capacitor, resistor and a diode. I'll put me mind to it again. It was for checking the output from the high and low speed stator coils. From memory, they should be about 300v.

I guess it converted the AC to a DC level with the resistor as a load to measure the voltage across?

jw. · 20-05-2006, 10:34 PM

Here you go.

Years ago I posted on Ribnet the operation of the ignition system. I'll go and have a look for it.

jw. · 20-05-2006, 10:39 PM

Connect the meter from A to B and set it on DC about 500v range. The circuit is just a rectifier. The capacitor is pumped up by the coil current so that the voltage can be measured. The resistor across the capacitor allows the capacitor to discharge so if the voltage from the coil reduces the capacitor voltage can follow. We're talking stator coils not ignition coils.

Edit: Linky

JamesM · 20-05-2006, 10:39 PM

Half wave rectifier, smoothing and some load.

Dan · 21-05-2006, 01:05 PM

Dont know if this makes any difference or not but I`ve just been reminded that last time out crawling out from the slipway in the 8knot zone the engine sounded like it was pulsing ie rising and falling by a couple of hundred rpm (in gear), I didnt think anything of this until know, I guess its part of the same problem, does that change anyones thinking?

Gav · 21-05-2006, 04:24 PM

Quote:

Originally posted by Dan
Dont know if this makes any difference or not but I`ve just been reminded that last time out crawling out from the slipway in the 8knot zone the engine sounded like it was pulsing ie rising and falling by a couple of hundred rpm (in gear), I didnt think anything of this until know, I guess its part of the same problem, does that change anyones thinking?

mine has been doing exactly that too

Carl · 21-05-2006, 04:41 PM

both of mine did that aswell,i think its just something they do at certain revs,know doubt there is a technical term for it

scottyboy · 21-05-2006, 04:58 PM

I was told that is the prop getting "good" and "bad" water" if you run a fairly tall pitched prop?

scottyboy · 21-05-2006, 04:59 PM

Quote:

Originally posted by jw.
Connect the meter from A to B and set it on DC about 500v range. The circuit is just a rectifier. The capacitor is pumped up by the coil current so that the voltage can be measured. The resistor across the capacitor allows the capacitor to discharge so if the voltage from the coil reduces the capacitor voltage can follow. We're talking stator coils not ignition coils.

Edit: Linky

Cool! Thanks JW!

Burty · 21-05-2006, 08:36 PM

Quote:

Originally posted by Dan
Dont know if this makes any difference or not but I`ve just been reminded that last time out crawling out from the slipway in the 8knot zone the engine sounded like it was pulsing ie rising and falling by a couple of hundred rpm (in gear), I didnt think anything of this until know, I guess its part of the same problem, does that change anyones thinking?

nah they all do that dude but you dont really notice unless u have the offshore leg

Silversurfer · 23-05-2006, 02:37 PM

Both of mine did that as well