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470 Merc I/O


Roughrider IV

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I can tell you the two engines I will never own again... Newer model, mid range, Merc outboards and this 3.7 liter I/O.

I don't have much experience with them, since we just bought the boat this spring. Since we bought it though I've only had it out twice, been chasing gremlins all summer. I did about the same research you did. Mercrusier had a good idea, make a motor that was between the 3.0 and 4.3. Problem is they designed the motor. The one thing I am concerned about in motors is the maintenance/repairs. Not only is it dificult to access a lot of the components, the only place you can get the parts from is Mercruiser, so bend over. So far this summer we've replaced: Exaust manifold and riser(knew that was bad when we purchased but we got a deal because of it), carb, entire ignition system, and we should replace the water pump, as it is leaking out the weep hole, but that entails pulling the whole motor. At this point we decided to run it, and when the inner seal goes, throw a remand' motor in it(since we'd have to pull the motor either way).

To give a true example of how I feel about this motor... I found a boat localy for sale that was junk, needed a transom and stringers, but the 4.3 V6 and outdrive were fine. For $1500 I was thinking about buying the boat, ripping the motor and outdrive off and scrapping the rest and instlling the motor in our boat.

I'm sure there are people out there that have never had a problem with their motor and think they are great. For my money though I'll avoid them like the plague from now on. Just another example of good idea, bad execution.

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I just bought a new to me boat this spring. I looked at some really nice Grady White walk arounds that I fell in love with but they had the 470 or 490 in them. I stayed away from that motor. It is a Mercruiser aluminum block with a head from a Ford 460 (1/2 or one out of 2 heads from the 460. That part may not be bad and performed well but most or maybe all use a closed cooling system. Early models had a 3 inch heat excahnger which was undersized. So check if it has the newer 4 " round exchanger. The other problem is due to the closed cooling there are 2 water pumps on the motor double stacked on the front. They arr notorious for leaking seals and expensive to fix as it requires the motor to be lifted to get the pumps off and seals changed. Check for antifreeze in the bilge or bottom of the pumps at the front of the motor. The 3 problem is they use some kind of generac to make 12 volts instead of an alternator. They are also very expensive to fix and you can buy a kit to convert to a regular alternator.

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The 470 was Mercruisers response in the mid 70's to the thought that they were not going to have access to automotive engine blocks in the future. It also appeared as the 485. Had the closed cooling to prevent issues from the mix of different alloys when used in salt water. The above post is correct, because it was a Mercruiser design some parts are only available through Mercruiser and as the years go on, parts become less available.

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