Starter problem only when hot

[Merulius]

I have intermittent starting after 20 years on the moody 346. Fine first thing in the day. Then after a few hours motoring it's zilch when trying the key ignition. Something that gets hot is the culprit? Starter is 3 yrs old. Solenoid on top of it is original 37 yrs. Batteries 2 yrs. Alternator one year. Either no.1or no.2 showing full 13 volts when failed to start.
The big master switch is 4 yrs old. It's not getting hot. But feels strangely loose inside this year.
Tightened all battery terminals and anyway don't think a hot terminal can do this.
Am thinking of shorting the solenoid terminals to see if that's explaining this....or calling an expensive mechanic in split Croatia marina where it's costing 120 euros a night!
Any ideas appreciated.

 

[oldmanofthehills]

I suspect you are on the right track and the starter is failing to engage due to a heat related alignment issue. The solenoid should click when you turn the key - though it will need an assistant to turn key while you listen by engine.

Shorting power terminals might give you info. If it starts then it is not the starter itself, so you can then work back to solenoid etc

 

[Sandy]

Hello and welcome to the forum.

The make and model of the engine, starter and solenoid would be really helpful. The make of vessel is not really relevant.

Do you have one of these infra red temperature sensors that you could monitor how hot things get?

How long does it take before you can start the engine again?

 

[Boater Sam]

As its the oldest part and symptoms point to it, solenoid would be my first call.

 

[Merulius]

Thanks ybw people.
It's a mitsubishi 35hp. Marinised by thorneycroft.
After 2 hrs it's cool enough for the starter to work again.
There's no click .
I've just replaced the main switch as I had a new spare. Working now on re-making a dodgy looking main earth attached to the engine. It runs steadyat 80 degrees as it has done for 20 years.
I have read that wire terminals which looks ok might in fact need new ends so am working through the ones that get hottest. Then a test.
Thanks again.

 

[oldmanofthehills]

Sound could be solenoid failure. The coil can expand and contact as temp changes, then a poor internal connection goes duff.

Main wiring loom less likely to be issue as wiring not loaded thus heated towards solenoid except at moment of starting

 

[Merulius]

I suspect you are on the right track and the starter is failing to engage due to a heat related alignment issue. The solenoid should click when you turn the key - though it will need an assistant to turn key while you listen by engine.

Shorting power terminals might give you info. If it starts then it is not the starter itself, so you can then work back to solenoid etc

Just shorted the

Sound could be solenoid failure. The coil can expand and contact as temp changes, then a poor internal connection goes duff.

Main wiring loom less likely to be issue as wiring not loaded thus heated towards solenoid except at moment of starting

Yes I just shorted the solenoid and got a loud whirring noise. No starter. I've replaced the master switch and all nearby old wire terminals. Now it won't start even when cold. Best order a mechanic now!

 

[Alex_Blackwood]

Just shorted the

Yes I just shorted the solenoid and got a loud whirring noise. No starter. I've replaced the master switch and all nearby old wire terminals. Now it won't start even when cold. Best order a mechanic now!

Sound's like it is not engaging possible because the solenoid isn't throwing starter gear. Depends on which type of starter motor fitted pre engaged or not?
With second thoughts you possibly by-passed the operation of the solenoid, depending on exactly what you shorted so it would not engage anyhow.

 

[oldmanofthehills]

Time to take starter off and oil grease and clean the cogs.

Myself I prefer to hire agile young fit monkeys for such constrained tasks if I have the funds. Cars and vans are easier than boats in that respect

 

[billskip]

Sound like it's the starter solenoid on top of the starter motor...this would normally indicate it's a pre engaged system.
When you turn the key the solenoid moves a bar /fork internally which first puts the bendix in the flywheel ring teeth the bar continues to move and makes contact with the internal heavier contacts which then excites the starter motor...you excited the starter by short the connection and heard a loud whirring..this would first indicate the solenoid coil/connection is faulty or the contacts inside are burnt.
I suggest you remove the solenoid (normally 2 screws) and carefully disconnect mechanical fork mechanism and inspect it it may have the part/spec stamped on it.

You should hear a klick from the solenoid if nothing else..but if you are alone put your phone on record and put it near to the starter....

Edit ...you may have accidentally popped a fuse when you shorted the terminals.

 

[howardclark]

I have intermittent starting after 20 years on the moody 346. Fine first thing in the day. Then after a few hours motoring it's zilch when trying the key ignition. Something that gets hot is the culprit? Starter is 3 yrs old. Solenoid on top of it is original 37 yrs. Batteries 2 yrs. Alternator one year. Either no.1or no.2 showing full 13 volts when failed to start.
The big master switch is 4 yrs old. It's not getting hot. But feels strangely loose inside this year.
Tightened all battery terminals and anyway don't think a hot terminal can do this.
Am thinking of shorting the solenoid terminals to see if that's explaining this....or calling an expensive mechanic in split Croatia marina where it's costing 120 euros a night!
Any ideas appreciated.

I don’t claim any expertise but certainly experienced very slow motor turnover when starting my old engine when it was hot. Never a problem when it was cold. Always managed to start it but there were a few anxious moments.
When I looked into it I learnt that wire resistance increases with temperature. In my case I had done away with a relay and I think I was challenging the ability of the wiring to carry enough current.
It may well be that there is a problem with the starter/solenoid, but I would first of all make sure the wiring is up to scratch and if you don’t have one put in a relay- they are cheap and pretty easy to understand. Only then spend real money!

 

[mikegunn]

The solenoid on a pre-engaged starter has two tasks. The first is to engage the starter’s pinion gear with the flywheel rim gear and its second function is to close the contacts which send electricity (lots of it) to the starter motor. To be effective in its functions the solenoid first has to receive a good kicking, in the form of an electrical instruction from the engine’s start switch. A solenoid can make an initial demand of up to 20 Amps when it throws its pinion gear into engagement. Any tardiness in its action often leads to the starter contacts failing to contact. The electrical supply to the solenoid often takes a tortuous and lengthy journey from the start battery’s terminal through the master switch, up to the engine’s start switch and back down to the solenoid. I’ve seen runs of more than eight meters on quite small boats. That may be fine when the wiring is new but with age comes increased resistance. There is fortunately, in most situations, a very simple solution. If a relay is introduced close to the solenoid it can be used to dramatically shorten the load path from the battery to the solenoid actuating terminal. The electrical supply from the start switch is used solely as a signal to activate the relay, which will demand little in the way of current.
A suitable 12V relay can be had from any motor factors. Short lengths of 2.5mm2 wire from the battery side of the solenoid to the relay and back to the solenoid’s actuating connection will suffice.

Mike

 

[Merulius]

Thanks for the latest ideas. My starter is less than a meter from battery. I will check fuses. Mechanic is coming tomorrow late morning!

 

[capnsensible]

What a good explanation. I've been involved with fitting such a relay on three yachts with yanmar engines including one of my own. Works a treat.

 

[oldmanofthehills]

The resistance of wire will not increase with time however long they are. All terminals and connections however will be vulnerable corrosion and thus possible increased resistance, particularly in salty atmospheres, plus of course vibration loosening connections over time

 

[Rappey]

The big master switch is 4 yrs old. It's not getting hot. But feels strangely loose inside this year.

I have a project boat and also have lots of "boat stuff" which is usefull to refit this boat.
I fitted a used rotary master switch which didnt really feel right but seemed to work. Had engine starting problems, just a click.
Took the rotary switch apart, cleaned it, little grease. One back together it felt perfect. Engine turns over every time now

 

[Merulius]

Thanks for all the ideas. All working now after a couple of weeks to be sure. It was bad old wiring, 37 years old !
Mechanic and electrician in split Croatia were brilliant. Took solenoid to workshop. Cleaned and photographed, said it's been perfect.
Said my wiring is a disaster and renewed some. Added a relay and button for future eventuality, not used yet.
I will get rewiring of everything from the ignition done this winter.
Bill was 460 euro but I gave 500 as was so grateful we could continue our holiday!

 

[Metalicmike]

Have you checked the engine earth, my first go to place for starter problems. Also I had to swap a battery cable as it was turning to dust due to corrosion. ( battery cables tend to have hundreds of fine wire conductors that can degrade much faster than all your other wiring).