Mercruiser 260 issue

[Jhayes780]

Good morning everyone,

Yesterday I was out on my sea ray with a mercruiser 260 not sure of the exact year but I believe it’s an 80s model with under 1000 hours 912 to be exact. When we were cruising along everything was fine temperature was fine and then I started hearing kind of a grinding noise as soon as I heard it I turned it off, I had issues a couple weeks ago, so I was frequently monitoring the gauges and was not pushing the engine too hard. The oil pressure gauge dropped from 60 to 0 as soon as the noise started I turned it off immediately and the temperature gauge climbed in the engine started smoking, or let it cool down and then it would crank, but would not completely turn over, I think if I kept trying, it would’ve turned over, but I didn’t want to risk putting anything in more damage. Where does everyone think the issues could be, how much damage can I have done?

 

[stresspoint]

? any holes in the engine block , possibly a broken rod ,

 

[Jhayes780]

? any holes in the engine block ,

No holes that I noticed. I was also thinking rod. What’s the cost and labor on that. Is it a diy for beginners lol?

 

[stresspoint]

no idea on cost , i would get the motor out of the boat and asses what the damage is., grinding , not cranking and smoke does not sound promising for much salvage internally.
place your order for a short block if you don't have the skill set to rebuild a blown motor .

 

[Scott Danforth]

pull the plugs and try turning it over. if you have water in the cylinders, you are hydro locked.

if no joy, pull the drive and try. if the motor then spins over, look at your drive.

 

[Jhayes780]

no idea on cost , i would get the motor out of the boat and asses what the damage is., grinding , not cranking and smoke does not sound promising for much salvage internally.
place your order for a short block if you don't have the skill set to rebuild a blown motor .

It will crank and wants to turn over but won’t completely get there

 

[Scott Danforth]

Clean the battery connections and load test the battery

 

[Jhayes780]

Clean the battery connections and load test the battery

I don’t think it has to do with the electronic components

 

[Scott Danforth]

I don’t think it has to do with the electronic components

If your cranking RPM is over 250RPM, then maybe

Which ignition system do you have. If you have points, did you service them?

What are your compression numbers? Should be between 125 (low) and 150 (new)

 

[Bondo]

No holes that I noticed. I was also thinking rod. What’s the cost and labor on that. Is it a diy for beginners lol?

Ayuh,.... That's when you replace the entire long block motor,.....
Or a full on rebuild at a machine shop,....

 

[dubs283]

Completely lost all oil pressure means you check oil level/quality.

Was there any engine oil present in the bilge?

 

[Jhayes780]

Yes, there was a slight amount in the bilge, but after it cooled down, the oil pressure went back up.

 

[dubs283]

after it cooled down, the oil pressure went back up.

I thought you haven't got it running again?

 

[Jhayes780]

Sorry, I haven’t fully got it running but when I turned it back on the gauge settled and rose back up

 

[dubs283]

Okay, what I glean from your posts is the engine (or something else) made a huge racket, oil pressure guage dropped to zero, temp guage rose, you shut the engine down and now it turns over/rotates but will not start/run. Correct?

Now you say you turn it back on, key in run position engine not running and the oil pressure guage reads normal? Are you cranking/turning over the eninge and the guage reads normal?

 

[Jhayes780]

Okay, what I glean from your posts is the engine (or something else) made a huge racket, oil pressure guage dropped to zero, temp guage rose, you shut the engine down and now it turns over/rotates but will not start/run. Correct?

Now you say you turn it back on, key in run position engine not running and the oil pressure guage reads normal? Are you cranking/turning over the eninge and the guage reads normal?

Correct on all. Ya the oil pressure gauge read higher when cranking and being towed. Correct it will not start but cranks over. But due to smoke I didn’t really want to try to hard to get it completely turned over

 

[dubs283]

If it got hot enough to smoke there's a chance of melted casing on wires in the harness. May account for the oil pressure guage reading zero

If engine oil is full/clean you need to source the cause of overheat. Sea water pump impeller investigation is the first step