Re: Mercruiser 470 questions
There are far more experienced members here to pass on their wisdom than I, but I will pass what I know living with twin 470’s in an ‘85 Sea Ray. It is easy to start an argument about these motors.
First, the boat price should be free for the hauling if it has truly sat for 8 years with no activity, winterized or not. Garage rot is insidious and EVERYTHING will need fixing no matter what the appearance. Prepare to spend what the “book” value is this boat at a minimum just to get it dependable. On the other hand you can replace everything and still be money ahead compared to a “new” boat. But still, your neighbor should be paying you to haul it off.
I would still run away from something sitting for 8 years, better to have 1,500 hours on a mid 80’s boat and be well maintained.
Good: 470’s have good power/weight, have good torque and are very fuel efficient and you can still get parts, but sometimes have to hunt for them. When well maintained and watched every time you use it they are good power plants. It has a closed cooling system. They benefit greatly from the electronic (Pertronix) ignition conversion (plus wires and coil) and a 4” diameter heat exchanger, new top notch starter and a well done carb rebuild by some one that knows what they are doing.
Bad: It has a steel Ford cylinder head and Mercrusier aluminum block, not a good combination of materials due to different thermal expansion rates. The engine coolant pump is driven off the camshaft. There is a dual seal that keeps the oil and water separate and this can wear out or groove the shaft and let water in the block, it can be repaired with Speedy Sleeves. It is susceptible to overheating, more so than other motors if all parts of the cooling system are not maintained well. If you overheat it, it will likely ruin the head gasket in very short order and cause all the usual damage. Do the alternator conversion, it is far cheaper than even keeping the coolant cooled voltage regulator.
Check out the Breezeworks site, it is dedicated to the 470. Find a mechanic you trust and has lots of experience for a buyer’s survey, don’t go in blind, the engine is not your only worry.
