Multihull starting engine

[BobFord]

Help appreciated- (2 ) Yanmar 4JH4HTE. Trying to start Port engine,connected multimeter to battery ,cold 12.8v, turn starter, no start ,no change to voltage.

Switch on 'bridge' to Std motor and battery. still no start.still reading 12.9v.
Started Std motor and rev. up .Bridge still on.
Port motor now starts and reading settles at 14.5v

I determine that
-port battery ok
-port starter switch ok
-port solenoid and starter motor ,ok.
-port alternator is charging

Any ideas ,please ?

[jimbunyard]

Proximate cause; loose connection somewhere, possibly on the low amperage side.

Ultimate cause: possibly improper wiring between the two engines

Just guessing without more information.

[Tupaia]

Is this a recent fault condition? ie has the port engine started before OK?

Are you testing the voltage at the starter or on the battery?
There maybe only one start battery on the stb side and a pathmaker set above 12.9 volts between the start battery and the port engine or there is a fuse or breaker between the cross connection from the stb battery and the port battery but not between the stb battery and the port engine.

But just guessing.

Make a detailed wiring diagram and all will come clear.

[JustMurph]

Check the voltage at the starter motor on the port engine. I'd bet there is no power there. Now trace the wiring back the battery....there will be something wrong between.

[sailormed]

Check the battery neg. connection to the engine.

[BobFord]

Many thanks for the suggestions ,Guys . I will progressively work thro' the options. Tupaia- the starting failure has only recently occured after 4 years of new battery. Normally ea. engine is self contained but the "bridge" has been a useful item when batteries are suspect.
Regards, Bob

[BobFord]

Hi to -sailormed , JustMurph ,Tupala, jim bunyard. I have carried out inspections and tests as noted by you Guys . motor not running , battery 12.8v , starter motor 12.8v, wiring Port to Std bridge seems intact and original ( it was installed by a qualified Engineer and is very complex , to my mind , i'm a house Builder !! ) All connections to batteries ,start motors ,alternators , regulator, seem normal. Also inspected starter switch in Pilothouse - seems original but can't imagine what's inside. The main thing that bothers me - the Port engine will start with bridge to std. battery on but only if std. engine is running at more than 1600 revs( charging positive ) Any further ideas appreciated. I note that I was in Med . several times and LA ( assume Los Anglese ) And base now is Rivergate in Brisbane .

[JustMurph]

Hi Bob,

I think my next check would be to see what happens to the voltage at the port starter motor when you try and start it (with the Stbd engine off). It’s possible that a bad connection to the battery could allow 12.8v at the starter under no load, but not be able to get enough power through to start it. Under a normal starting load you should see maybe 9-11v at the starter. If this was your problem you’ll be seeing say 5 or less.

I’m tied up this arvo, but if you get stuck I could pop down to Rivergate and give you a hand tomorrow or Friday. I work just down the road.

[BobFord]

Hi Just Murph,
Much appreciate your ideas and suggestions. That I will try.Boat is still North , Kepples , e.t.a. Rivergate 1st week Dec. I'll keep you posted and if stuck with problem i'd appreciate your help at Rivergate. I believe that I can send a message to you via this station. Cheers,Bob

[JustMurph]

No problem at all Bob. Let us know how you go!