Mercruiser 4.2LD Non start help wanted

[dave1dpc]

My sealine is shod with twin engines. I have put up with a problem for many years even having a Merc. specialist to no avail. In order to start my port engine I have first to start my starboard then use the LINK switch. We have checked and cleaned all the earth connections. Even after connecting both battery banks together 4x120amp And taking a separate supply directly onto the starter motor to no avail. Both starter motors have been serviced and swopped over. The engine is relucted to crank over but will burst into life at a touch from the LINK switch. The engine can be nursed to fire up without the link switch once up to temp. I have tried shorting out the isolator switch and changed it. This starting procedure is no inconvenience but after 10 years sooner or later it is going to bite me in the bum.. I am in the process of sourcing my water intake through hull as fitted to shaft drive engines [not related to start problem]

 

[Mr Googler]

when you went direct....that was just ve+?

I’d renew ve+ and ve~ battery cables to that engine

could be black and nasty inside either or both cables

 

[volvopaul]

My sealine is shod with twin engines. I have put up with a problem for many years even having a Merc. specialist to no avail. In order to start my port engine I have first to start my starboard then use the LINK switch. We have checked and cleaned all the earth connections. Even after connecting both battery banks together 4x120amp And taking a separate supply directly onto the starter motor to no avail. Both starter motors have been serviced and swopped over. The engine is relucted to crank over but will burst into life at a touch from the LINK switch. The engine can be nursed to fire up without the link switch once up to temp. I have tried shorting out the isolator switch and changed it. This starting procedure is no inconvenience but after 10 years sooner or later it is going to bite me in the bum.. I am in the process of sourcing my water intake through hull as fitted to shaft drive engines [not related to start problem]

First of all don’t fully use the seasick to feed the engine as you will be buying a new drive shortly as the water passage cools the leg .

sound like you have a bad earth problem, have Sealine taken the earth from battery to one engine I’d guess the good starting one then a link cable to the engine in question, try a jump lead engine to engine for a start , then check the voltage at the starter terminals when cranking , if it’s low then it could be the starter that’s worn out sapping the amps .

 

[QBhoy]

Agree with the above completely. Take a jump lead from a known hood earth and see.
Again, don’t disrupt the water intake system, it’s not going to end well.
Is there any chance you’re getting water into that tough to start engine ? How’s the coolant level over time ?

 

[dave1dpc]

when you went direct....that was just ve+?

I’d renew ve+ and ve~ battery cables to that engine

could be black and nasty inside either or both cables

Both engines are strapped together with heavy guage earth wires. All cables checked for resistance.

 

[dave1dpc]

First of all don’t fully use the seasick to feed the engine as you will be buying a new drive shortly as the water passage cools the leg .

sound like you have a bad earth problem, have Sealine taken the earth from battery to one engine I’d guess the good starting one then a link cable to the engine in question, try a jump lead engine to engine for a start , then check the voltage at the starter terminals when cranking , if it’s low then it could be the starter that’s worn out sapping the amps .

All wires checked for resistance. Both starters overhauled and swopped over. Both engines paired with earthwire. Will try the cranking voltdrop. The rubber pipes [25mm i.d ] up through the legs are after a few seasons inadequate and getting to the gimble end twixt the engines is not easy without removing the engines . After the plastic inserts are fitted into the ends of the rubber pipe this restricts the pipe to about 20mm. There is very little heat transfer from the rubber pipes into the legs. There is however a copious flow through the legs from the exhaust return. Surely the lack of cooling is no different from a car dif. or gearbox which are not water cooled? Perhaps I could easily fit an outdrive shower.

 

[spannerman]

You can have a through hull water intake, many boats are built with this set up on Mercruiser. The essential thing is that you have to cut 2 inches out of the water hose between the drive and transom, this allows water to pass through the drive and out again for cooling, and obviously you will have to fit a blanking plate on the inside of the transom where the original hose comes in.

 

[James L]

All wires checked for resistance. Both starters overhauled and swopped over. Both engines paired with earthwire. Will try the cranking voltdrop.

I don't think checking the wires for resistance will be enough, it would show a break but as far as I know it won't show up partial corrosion etc as the ampage used for the resistance check is so small.
I changed all the battery connections last year as one engine was slow to start and it's like a new engine since.
Very similar symptoms to yours, I sometimes had to start the other engine first, I already have both alternators charging all 3 battery banks, so similar to your link switch and it would always start then. I replaced the battery thinking that was the problem but no difference.
Since you already ran a jump cable straight to the starter, I imagine it would be the neutral connection somewhere causing the problem.

 

[dave1dpc]

You can have a through hull water intake, many boats are built with this set up on Mercruiser. The essential thing is that you have to cut 2 inches out of the water hose between the drive and transom, this allows water to pass through the drive and out again for cooling, and obviously you will have to fit a blanking plate on the inside of the transom where the original hose comes in.

Thanks all for feedback....Spannerman could you please elaborate on the cooling of the legs thank. Good to see you and volvo Paul are still active after my absence from the forum for 5 years.

 

[spannerman]

The leg is cooled by water passing through it as you drive, but it needs an exit, so if an alternative water inlet is used then it means there will be a blanking plate on the inside of the transom where the water hose goes from the transom to the engine. This would then block the passage of water through the drive, so Mercruisers workshop manual specifies on such installations that the external hose from the gimbal house to the transom has a section cut out of providing an exit for the water coming up through the drive this allwing corculation of cooling water. Hope this helps.

 

[dave1dpc]

The leg is cooled by water passing through it as you drive, but it needs an exit, so if an alternative water inlet is used then it means there will be a blanking plate on the inside of the transom where the water hose goes from the transom to the engine. This would then block the passage of water through the drive, so Mercruisers workshop manual specifies on such installations that the external hose from the gimbal house to the transom has a section cut out of providing an exit for the water coming up through the drive this allwing corculation of cooling water. Hope this helps.

Thanks.. I was considering a outdrive shower but this removal of 2" of the rubber pipe is an obvious solution.

 

[spannerman]

We fit drive showers on boats where the top of the drive rises above the water when planing to assist cooling when its either a
heavily loaded drive or fast, high horsepower installation.