Merc 470 Should I Buy? Thoughts and common issues with this motor?

[anderso8623]

I know the common consensus is that this is the worst Mercruiser they made; but is it all that bad? I have a line on a 1984 Sea Ray Sundancer with twin 470's. The boat is in overall great condition and a fair price. It is the style boat I wand but am concerned about the motors. Not that the ones in this particular boat are questionable, more of the reputation.

What are your thoughts on the motor?

What common problems did they have/should I look for?

Any and all advice is appreciated.

 

[tpenfield]

Twin 470's sounds like double trouble

 

[Scott Danforth]

the motor is a poor execution of a good idea

the main issues with the motor are:

• iron head on aluminum block
• floating bores
• soft cam nose
• cam driven water pump
• motor is obsolete

due to the iron head and floating bores, if you overheat by as much as 10 degrees, you can and will spit the head gasket.

you can get aluminum heads for the motor (Ford 460 head) and modify it
you can have a custom bore girdle made and welded in place for the floating bores, however this would only be worth it if you really love the 3.7 motor.
not much you can do about the soft cam nose, except speedy sleeves or have the cam welded and re-ground.

because the motor is narrow, on twins, you most likely can not repower either unless you consider twin 3.0's or small in-line diesels. your motor spacing would need to be over 36" to go to V6's or V8's

being a 34 year old SeaRay, you really should get the hull surveyed. It will not be uncommon for the foam to be water-logged and the wood to be wet/rotten

a rotten hull with twin 470 motors would really be a bad purchase

 

[kenny nunez]

I had a customer that had one of like you are looking at. If the hull is solid repower with a big block package and be done with it. To just remove the port engine you have to remove every thing off the engine except the manifold. Then you will need a transfusion to replace the blood loss! That Searay was built from the engines out.