Short Leg!!

TwoStroke · 20 Aug 2003

Yes - but make sure power is off. When replaced my batteries, connectors were also covered in crud. Cleaned up, re-connected and greased.

Checked fuses in dash and connectors and fuses were the same. Wire brush and wire wool.

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duncan · 20 Aug 2003

I can understand the electrical side, and as others have said this needs sorting as it shouldn't be that significant (although it may well be apparant). However it should not have an impact on the engines power output - ie you have a problem!
Surely the leccy thing isn't impacting the HT side as well?
Coming off the plane due to triming is another issue - I thought this thread about 'operating the trim' to trim out a fully planning boat ie you would expect both engine revs and speed to increase for a given throttle setting on a petrol boat.

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martynwhiteley · 20 Aug 2003

Sound's like it must be affecting the HT side.

Or else it would seem a little too coincidental for the boat to always fall of the plane every time the trim button was pressed.

Does the leg actually move when trimed Al? I suspect not.

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Alistairr · 20 Aug 2003

The guage moves, wether or not the leg actually moves , idon't know,
The boat doesn't fall off the plane, not unless i hold the button for a few seconds, but only because of lack of power.
Duncan i know how too trim a boat out, i have a sportsboat myself so it is important to trim the boat as far as poss. to get as much of the hull in the air as possible. I know what it feels like too have the leg trimmed too far out or too far in..
Remind me Martyn which is the HT lead.

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Petrol Rules..

martynwhiteley · 20 Aug 2003

If the guage moves, then the leg must be moving.

The HT side provides power to the spark plugs. The HT is generated by the 'Coil', which has one HT lead going to the central connection on the Distributer Cap, from there, the individual HT leads take the 'timed' spark to each spark plug.

If the LT (12v) supply to the coil drops sufficiently (say less than 9v), the coil will not generate enough 'HT' to produce a spark, thus the engine will start to missfire and lose power.

It would appear that the leg motor is working, however they do draw a lot of power, and I can watch my volt meter drop a significant amount when I press the trim button. Due to either bad connections, poor battery, or a faulty alternator, it seems that the high load required by the trim pump is reducing the LT voltage below that required by the coil.

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Alistairr · 20 Aug 2003

I can't see then how HT leads could be the problem. The power to them must be dropping because of something else.
Are boat engines not like car engines where you can run them with the battery disconnected?

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TwoStroke · 20 Aug 2003

If the HT leads haven't been replaced for some time and corroded, then they will amplify the voltage drop when any load is put on the engine.

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duncan · 20 Aug 2003

absolutely!
(1) what's your voltage at the battery after it has been left standing for an hour plus - ie when you first get to the boat?
(2) what's the voltage with the alternator at full output speed - around 1500rpm?
You will find a volt reading window on most chartplotters and fishfinders somewhere!

I suppose it is possible that the trim is binding in someway to overload the motor - ?

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martynwhiteley · 20 Aug 2003

The easy test would be to put a volt multimeter (don't refer to a dash volt guage, they're way out) across the battery when the trim button is pressed.

If I'm right, then the voltage should drop from about 14v to below 10v with the engine running.

Because the battery IS connected, it will control the LT voltage, so even if the alternator was running ok, a large load on a duff battery could reduce the LT supply to the coil enough to cause a major loss of HT current.

Also, it's possible that the pump motor is s*a**ed and is drawing too much current.

This would almost be like just shorting out the whole LV electrical system when the trim switch was pressed. Because they have large cables and big fuses, it's pssible that pushing the trim switch for only a few seconds would not be enough to blow the fuse, however the cables would get pretty hot.

You need to check all the main connections, check the voltages running (13.5 to 14.5 v) and static (11.5 to 12.5v), try a different battery perhaps, check the coil connections, HT leads, and the voltage drop when the trim pump is used. Also confirm that the leg is moving normally.

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martynwhiteley · 20 Aug 2003

Great minds and all that Duncan....!

I was told of a case where the 'lift' and 'lower' hydraulic hoses had been connected the wrong way round on the pump (black for up, grey for down on mercruiser).

The fault was not noticed during (dry) PDI 'cos it still went up and down, but in operation, the gearing was obviously all to cock, and the pump was severly overloaded when trying to lift the leg.

Just a thought...?

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Alistairr · 20 Aug 2003

Cheers Martyn and Duncan, I shall be going up to the boats for the weekend so shall check things over and start cleaning and greasing.

Thanks for all the advice.

Cheers

Allistair..

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hlb · 20 Aug 2003

I want a crome coloured one with two trumpet thingies

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Haydn

Alistairr · 20 Aug 2003

Something like this

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hlb · 20 Aug 2003

Yep, a bit like that, sept I'd like them to fit the same holes I've got please. There two seperate horns and only screwed down at one end. EErr. The end where your mouth would be, if it was a trumpet!!

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Haydn

Alistairr · 20 Aug 2003

What about 2 of these side by side then.

Hows about that then?????

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Petrol Rules..

Alistairr · 20 Aug 2003

You didn't expect that so quick, did you?

Me thinks that deserves a personalized Burgee..!!!!

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hlb · 20 Aug 2003

Yep. Now I just need one long one and one short one.

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Haydn

Alistairr · 21 Aug 2003

Gawd, you're not asking for much are you!!!!

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Alistairr · 21 Aug 2003

Something like this-

Now can i have a burgee.

Once somebody finds me a stainless staff.

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Canboria · 21 Aug 2003

Is this what you require

Short Leg!!

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