496 Mag engine burning up starters

[skiprima]

496, Bravo 3 outdrives. Had the lower unit gears replaced this spring. Boat used appox. 6 hours since the work was performed. After a short 1 hour ride, and then a break for dinner, the port engine would not start. The starter was making a high pitched whirring sound. Pulled the starter and found a broken part in the starter. Replaced with a new starter-a factory replacement- and tried to start the engine. After 2 cranks the new starter let go and began to make the same whirring noise as the first. The engine never turned over. Both people present described it like something was binding up the engine.
Anyone know if there is anything related to the lower unit that could be binding up the engine preventing it from turning over? Is there gearing in the lower unit that would turn when you crank the engine? One mechanic thinks there is and another doesn't think so.

 

[Bt Doctur]

May be a leaking manifold allowing water into a cylinder or two. Pull the spark plugs first, then try turning the motor over.

 

[keokie]

As noted, the motor could be hydrolocked. As mentioned, I would pull the plugs first. If no water, I would pull the drive, then try to turn the motor. The lower theoretically cannot stop the motor, but you could still have a drive problem.

 

[tbirdvet]

I would use a socket and bar and see if you can turn the engine over by hand to verify if it is locking up. Was it the gear on the starter motor that broke?

 

[skiprima]

yes, it was a plastic gear in the starter that broke; twice.

 

[tbirdvet]

I did not realize that starters of that size used nylon gear ilo steel. Nylon is quieter but not as strong. I wonder if all new starters use nylon gears?

 

[skiprima]

Pulled the plugs today and did find water in a couple of the cylinders. Turned the motor by hand and felt what seemed like a lot of resistance. I had the serpentine belt off and the motor turned hard compared to the other engine, with everything on it. That engine turned easily.
I am not going to try and crank the engine for fear of burning up another starter.
The boat comes out next week and the drive comes off.

 

[rabyers1]

Did you check the crankcase oil (dipstick) to see if there was any water in there?

In any event you are going to want to get the water out of those cylinders ASAP and get them lubed up real well. Rust will play havoc with your piston rings and other parts. I let the water sit in a couple of my cylinders two years ago and now I have a shiny new $10K engine in my ER as a result. I started with the same exact symptoms as you - tore up two starters and then discovered water in two cylinders from deteriorated exhaust manifolds. Couldn't get back to the boat for a two weeks and the engine was rusted up solid by then.

 

[tbirdvet]

Not clear to me why the drive repair would fix water in the cylinders. Sounds like something else.

 

[GMAN1]

Listen to the guys above except TBIRDVET. Most likely your exhaust has failed and allowed some water to leak back on your pistons. You cannot compress water hence the broken starters. Pull the plugs and crank the motor over to get the water out asap. You can spray some mystery marvel inside each cylinder to make sure it is lubed up until someone can address this issue for you. If not you will be paying for a new long block.

 

[skiprima]

Thanks everyone for the replies. I have taken the plugs out and sprayed the pistons since the incident. I should know something by Friday when a marine mechanic looks at it. We were pulling the lower units anyhow for maintenance, so the first step will be to pull the troubled engine drive and then see how easily the engine turns by hand, eliminating the lower unit as a problem. If the mechanic feels like it is not bound up, he can start the engine with the new starter in place.
I will post a follow up when I know something definite.

 

[skiprima]

Thanks to everyone for their replies. The boat will come out of the water on Thursday. By Friday I should have an answer and will post what the marine mechanic finds out.

 

[skiprima]

No update yet on problem. The boat was taken out today and the Mercury Mechanic, who promised that he would come down immediately when the boat was out, now tells us he cannot look at the boat until the 11th of July.

 

[Big Island Lifer]

No update yet on problem. The boat was taken out today and the Mercury Mechanic, who promised that he would come down immediately when the boat was out, now tells us he cannot look at the boat until the 11th of July.

Ugh! Don't ya hate trying to get mechanic around a holiday!

Best of luck with your repair.


Sent from my iPhone using Tapatalk

 

[skiprima]

no definitive answer to problem
The mechanic felt the resistance on the engine and determined more water was still in the cylinders. He repulled the plugs and then cranked the engine, something I was wary of doing. He had warned me of cranking the engine without the plug wires being grounded, something he did with his own harness.
We put a muff on the lower unit and ran the engine. No internal signs of damage that would have led to water in the cylinders.
The mechanic still feels it came up through the exhaust. One thing I did see, before pulling the lower unit, was a lower exhaust bellow, that loosely connects the engine exhaust to the lower unit, was missing. This bellow is held on with a hose clamp. When the lower unit is in the down position, this short piece of tubing directs the exhaust flow into the lower unit. It is not a tight connection, which allows the lower unit to pivot without ripping the bellow off. The mechanic did not think this was the cause of the problem with the bellow missing, but what I saw was a straight piece of pipe coming out the transom that was just asking for water to come in.
The lower units came off for maintenance and this lower bellow was replaced, along with all the other bellows.

 

[tbirdvet]

The exhaust bellows being off would not be the cause. In my engine it is not even used. Only impacts the exhaust noise/backpressure (minimal).

 

[Bt Doctur]

The day this happened were there a lot of people in the stern or was there some decent wave action.Water could come in that way.

 

[dlvwill]

Bravo 3's require that a exhaust "cuff" be used instead of a true bellows between the transom mount and bell housing. This is because the lower unit doesn't flow enough exhaust with the double shaft arrangement, this is to reduce exhaust back pressure. It is designed that way and isn't the source of your problem in this case.

 

[skiprima]

Found the problem, definitively, today.
I had the mechanic at the boat working on a smartcraft issue; a problem we hope is entirely independent of the water in the cylinder issue. While poking around under the dash, he reached around and tried to start the port engine. Immediately, we could tell the engine had locked up. There were no waves on the water, there wasn't anyone sitting in the back of the boat. After having started the engine at least a hundred times since it went back in the water, without incident; wham, we got hit again.
He pulled the plugs and blew quite a bit of lake water out of the engine. Whatever failed, it went completely today, given how much water came out. He has already ordered a new exhaust riser and mainfold for me.
As bad as that is, I am relieved to have found the source of the original problem- without any doubt now.
Now, if we can only solve the smartcraft issue.............