2015 Mercruiser 4.3 EFI issues.

[GhostriderL76]

Helping my friend get his boat he purchased last year sea worthy. He had it out a few times, both ending in issues. First the gear oil resevoir leaked and set of an alarm. Would this cause the engine to go into limp mode! New reservoir installed.

Second issue, low voltage. Diagnosed as alternator, most likely damaged when the gear oil leaked and coated the alternator. Replaced alternator. Have not yet run engine to test. Would the engine run poorly or quit, absent a solid 12+ volts? I'm wondering if he ran the battery down (inop alternator) and the ECM/PCM etc didnt like low voltage?

Third issue, we changed the oil, (suction pump) and the first quart was all water. 4+quarts of oil came out. So, where did the water come from? Last time the boat was out, the engine quit (low voltage?). Engine would crank, but not start. I'm wondering if the water came in the exhaust from the rear wake via absent exhaust baffles? Why no restart?

I wasn't there for any of this, so it's the best explanation I got / can give. The boat is in Phoenix soma frozen and cracked block probably isn't the reason for the water.

Thanks for the help

 

[alldodge]

Could use the motor serial number to verify, but being a 2015 it can go into power reduction (limp mode) if voltage is low. When voltage drops the PCM doesn't know what is wrong because so many things are showing problems

Low gear lube sounds an alarm and sets a code

Water in the oil could come from water going up the exhaust, but if it did that it would also hydro lock the motor. Most likely this is either a crack in the block or intake.

As to why no restart we will need more info

Start first by measuring the Battery voltage and see if it's close to 12.7V when not on a Bat charger

Assuming this is a MPI check fuel pressure at the rail, should be 43 psi with key on

Dump the fuel filter contents into a clear container to see if there is only clean gas

 

[ESGWheel]

Cracked heads / block / blown head gasket can also come from overheating. In addition to the above, also suggest to run a basic mechanical evaluation on the motor prior to trying to restart > a compression test.

And even prior to that, suggest pulling off the valve covers looking to see if that oil in the water has tuned to a milky goo covering it all. This will provide an indication of how long that water has been around. If it’s a milkshake in there, then its everywhere and more then likely means a rebuild.

If all seems to be good, ensure the other basic maintenance is done as well, like the impeller prior to restarting. There are lots of posts on this forum regarding these preseason items.

Good luck!

 

[GhostriderL76]

Thanks for the reply. We did a new impeller and gear lube. I've got a fuel pressure tester so I'll check press at the rail. i Haven't been back over to help him but will try this week. The boat has been sitting for 9 months so the oil that came out of the pan had ample time to separate. No Hydro lock according to the owner.

 

[Lou C]

Agreed with previous points made, if the boat was never in a freezing climate condition as you say then the more common ways for water to get in the oil is up the exhaust or overheating. Again as noted if up the exhaust it likely would have caused an obvious hydro lock with cyls full of water, overheating depending on how severe would damage the head gasket first then if it went to a more severe overheat cracked cyl heads are also a possibility. Both can let water into cyls and into the oil. A Qt of water in the motor oil is a lot. What concerns me is how long the water was in the oil. Ideally you want to get it out as soon as you know there’s been water in the oil & cyls. The fact that it sat there that long makes the possibility of a full rebuild more likely that just being able to go in and change head gaskets or even cyl heads. Unfortunately parts prices for these Merc built inboards are much higher than for the older GM marine engines.
Before taking things apart see if you can air pressure test the cooling passages.

 

[GhostriderL76]

Just thinking out loud here, would an exhaust manifold jacket full of water with an internal crack leak that much water, over months down the manifold and into whichever exhaust valve was open? There is a central knob (blue) to drain the cooling jacket down, which was not done prior to sitting. I opened the and drained it. Going over there tomorrow if it works out.