Posted: July 18 2006 at 13:04 | IP Logged

Recently replaced one of my Merc 470 engines on my 1983 270 Sundancer ... which is the 3RD engine replacement that I know of.  Have heard good and bad things about the 470 engine ... anyone have comments?  Wondering when the other 470 will FAIL.

Thanks

Posted: August 16 2006 at 04:30 | IP Logged

I had a 1986 19' Sea Ray cuddy with the 470 and I loved that motor. Huge torque, easily pull skiers up with half throttle. It has thousands of hours on it and still running great, the boat is 20 years old this summer and is used regularly and has never had anything but routine maintenance done to it (I had it for 16 years, now owned by a buddy, hope this doesn't jinx him!).

I have heard of the coolant seal issue, in fact when I bought my current boat in '02 (20 bowrider with 250hp 5.0)  the dealer's mechanic seemed suprised I never had this problem with my 470. We debated weather to change the gasket preventively just 'cause it's old, or leave well enough alone...

My understanding is the 470 engine was built because there weren't readily available automotive engines in the 4 liter size range back then. I understand it is aluminum block so closed cooling was required.

The motor was discontinued when similar displacement v-6 blocks became readily available from automotive manufacturers for marinization, and that is what we have today. So it was economics of mass production not equipment problems that did in the 470, or so I'm told.

My concern is short engine life might reflect loading or exhaust water intake issues with your boat that might affect any repower choice you make. Still, I would have to say the current v-6's with 200+hp would be my choice just because they are in production and seem to be pretty solid in performance and reliability. If you can get fuel injection for a reasonable price give it a thought... it makes starting turn key simple.

Doc

Posted: September 01 2006 at 13:34 | IP Logged

The 470 uses a cast aluminum block made by Mercury Marine and a 460 C. U. Ford cast iron cylinder head. (The same head used on the Ford 460 big block V8 only the 470 uses only one of the heads) Early 470's had problems with blowing head gaskets due to these metals expanding and contracting at different rates. This was partly solved later using a better head gasket.

HOWEVER combustion chamber temp is also controled by load. In other words yes the closed cooling system can keep the temp guage reading in the normal range, but if the engine is overloaded or run at near full rpm most of the time it will create overtemp in the combustion chamber and could cause head gasket seapage, or oil washdown by the piston rings.  These were the 2 main failures of this engine in my experience.

I formally owned a boatyard in CA. ofr 15 years and was a Mercury Dealer back then. We replaced many a 470/485 or 3.7L engine under warranty and worked with engineering in Stillwater Oklahoma. Mercury was forced to quit the engine  and move on. Yes some have worked well for people, but a larger portion did not. It appears  that engines used in heavy load application did not fair as well as those in lighter loads.  We rebuilt many of them since, and use the rebuild kit from Mercruy and a local machine shop. I would request a .002" extra piston to cylinder wall clearence over spec. this seemed to help with oil washdown as more oil would be loaded inbetween the piston rings and cylinder wall. Still if the engine ran hot it could be over quick. Also run the engine up to 3000rpm and make sure the timing is set properly both intial at idle and full timing at 3000rpm. I would set the timing back 2 degrees from spec. In other words if spec was 8 dergees at idel I would set our engines up at 6 degrees. This would help avoid detonation that is overtemp in the combustion chamber.

Make sure you are propped to the high end of your RPM range. Meaning if the rated rpm is 4500 to 4900 make sure your engine will get to 4900rpm at full throttle. This was what Mercury wanted us to do as a dealer.  Most of the people that were involved with this engine are no longer available. Now calling Mercury you will probably get someone not truely experienced with this engine, they would be reading out of textbooks.  There might me a guy named Horris in Stilllwater that is  still working there he is very knowledgeable with this model engine.

Good luck