1996 Mercury 225 Offshore Engine Failure

[Rooster Tail]

My 1996 carbureted Mercury Offshore needs a power head rebuild. The #2 piston had NO compression with a hole burned completely through it and all other cylinders were low on compression. No warning of overheating or oil injection problems. Only symptom was engine would stall and not run over 3200 RPM's. Has anyone had a similar problem with oil injected Mercury or other brand engine? Were there any recalls on this engine? Should I have the head rebuilt or purchase a factory rebuilt head?

 

[evin300]

Re: 1996 Mercury 225 Offshore Engine Failure

How many hours on this thing? What brand of oil? Whats is the Maintenance history? Did any amatuers play with the timing? or throttle linkeage setting? These motors dont usually commit suicide, But assisted suicide, yes!<br /><br />Oh and yes, I dont mean to be smart, as I realize that you must be quite upset about this, but I am curious, how long did you continue to operate the motor after the first symtom started occurring? In my experience, when these motors start talking, you had better be listening.<br /><br />As far as a 1)Shop rebuild, 2) factory re-build or 3) new OEM Powerhead, this subject deserves careful thought.<br /><br />How much damage to this motor? new pistons and overbore? then option 1) would be my choice, but I would have to have a lot of faith in the shop. <br /><br />Everything is trash except for the block? then option 2) would be my choice, provided it came from a reputable re-build factory/shop. <br /><br />Do you want the motor to be like brand new again, and pretend this whole thing never happened? and you dont trust anybody to rebuild one? then option 3) would be my choice<br /><br />I think ultimately it comes down to personal preference and $ of course, and remember that if you are going to shop around for the cheapest re-build, that cheaper isnt always better. which is epecially true with outboard motors.<br /><br />Good Luck, Rooster and tell us more about what led up to the demise of your motor, so we can all learn from this.

 

[Rooster Tail]

Re: 1996 Mercury 225 Offshore Engine Failure

Thanks for the comments. I am the third owner of this boat/motor so I don't have a complete maintenance history. The hour meter had about 160 hours when I got the boat last year. I have put only about 35 more hours since last September. The engine appeared to run fairly well when I first got it. It also has an oil light and temperature light on the dash that appears to be operational. I use Super Tech TC-W3 outboard oil. When the problem first occurred the motor was probably run for 30 minutes or so to get back to the dock. The mechanic changed the spark plugs and checked the fuel filters and carb. He then tank tested the motor which would then run to higher RPM's. I took the boat out again and in gear it would not run much above 3,000 RPM's so we immediately brought it back to the dock. The mechanic then did compression test on all cylinders. #2 has no compression, all other cylinders are low at between 100-110 PSI. The only abnormal problem that I had before this were as follows: <br />1. We spun a prop one day and spent several hours motoring in against an out going tide at low RPM's.<br />2. As we were coming in to dock at the marina on another outing the oil light came on. There was still plenty of oil in the tank but I topped it off just to make sure. The light didn't go out. The mechanic found some minor corrosion on the oil light contact. After cleaning the contact the light went off. He also checked for a plugged oil line. That was found to be OK.<br />Does anyone no if their are any Mercury service bulletins about problems with the diagnostic system on these engines?

 

[Big Rod]

Re: 1996 Mercury 225 Offshore Engine Failure

Probably DMMS...

 

[crazyray2]

Re: 1996 Mercury 225 Offshore Engine Failure

what ever route you go be sure to find why #2 ran lean....ie. hole in piston........carb need rebuild etc......

 

[Big Four]

Re: 1996 Mercury 225 Offshore Engine Failure

My guess would be two different reason and possibly a combo of both.<br /><br /> Sounds to me the timing was too far advanced causing detonation(firing to far ahead of TDC) and she was over proped. Over proping is about the nastiest thing you can do to a two stroke. When they can't turn rpms into the top end of the recommended operating range piston and combustion chamber soar right to the point of melting alum pistons.<br /><br /> Before you start figuring on just a one piston rebuild I'd be looking the rest of them over.

 

[Rooster Tail]

Re: 1996 Mercury 225 Offshore Engine Failure

To follow up on the last posting. This boat motor would turn about 5200 RPM at WOT before I started having this problem.<br />How long in hours or years do most 2 stroke outboards last before needing a major overhaul? When I get this engine rebuilt should I disconnect the oil injection and start pre-mixing the oil and gas? I have two 45 gallon tanks, is there a device made to facilitate adding oil to a large amount of gas during refueling or should I just use a large funnel? What happens if you run a little too much oil in the gas?<br />Any information is appreciated.