Mercruiser 470.

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JTK

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I've got a family member interested in an old project boat with one of these. It's the "190" version with a 4-bbl carb on it. Imagine a 3.7L 4cyl with a Ford 460 head on it and toilet sized carb. Anyway. Over the years, I've read bits and pieces of the inherent deficiencies with this series of engine, such as the belt-less charging system and potential undersized heat exchanger. Thing is, SO many boats in my area seem to have this engine. I guess when they sold them, they sold the heck out of them.

I've not heard too many negatives from those who have owned them long term. Curious to hear of BITOGers experience with this boat anchor.. I mean power-train!
 
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Solid engines, but you need to make sure that the boat has some decent clearance ahead of the engine so you can install a belt driven alternator conversion.

A new heat exchanger is always a good idea with those things. Modern ones can handle that engine.
 
If they end up getting it:

1. Do an alternator conversion if it hasnt been done already. The kits on eBay are pricey, but worth it if you cant fab up your own brackets.

2. Make sure it has the 4-inch heat exchanger, not the early 3-inch. The 3-inch exchanger simply cant keep up. Clean it with muriatic acid every other year or so. This can make a huge difference.

3. If they overheat, they blow the head gasket very easily. Use only a Mercruiser head gasket, not any old Ford 460 head gasket. A 460 head gasket intended for an iron head/iron block engine will fail in short order.

4. The later aluminum exhaust manifold was much better than the earlier cast iron units, as the cast iron ones tend to crack, allowing water into the cylinders, mainly #4.

5. The water pump is an impeller on the end of the camshaft. If its leaking you'll have to pull the front cover and various other bits off the front of the engine to replace the seals. If the cam seal surface is pitted, and it always is, either get a new cam, have the existing one sprayed and remachined, or use speedi sleeves.

6. The 4 bbl carb is similar, but not the same, as the ones used on the 4.3's, 5.0, and 5.7's. If your's needs help, rebuild it yourself, properly. If you get a new one, you'll be given the wrong one, I guarantee it.

Thats my advice after 15 years of ownership. The Breezeworks 470 forum has a wealth of knowledge, but its not a terribly active forum anymore, at least when I was there last (a couple years). If the engine was well maintained and doesnt have any huge problems (water in cylinders, cracked manifold or riser, etc) then it can be a decent engine. Very powerful for its size, and easy on gas. If it was neglected, severly overheated, sitting unused for years on end, or is one of the very early models, I'd look for some other form of entertainment, it will nickle and dime your sanity to death.
 
Thanks for the comments!

Dumb question: Not having owned an I/O powered boat in the family in decades (last was a 1970 OMC dual carb 4cyl), what pumps the 'sea water' through the heat exchanger and out the exhaust on this type of setup? I assume the cam driven water pump on the engine just circulates the antifreeze/coolant?
 
Well in a Mercruiser Alpha, there is a water pump in the lower unit. It runs all the time regardless of F-N-R. It's impeller should be replaced every 2 years or if you run the engine without water cooling/lubricating the impeller.
 
As the others have said above - it needs evaluation. If it's in decent shape and you are a handy back yard mechanic, no problem. If any of these conditions are not met, move along ...
 
Lotta good info there
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^ Some good reading for sure. Thank you. Opinions and experiences are all over the place with this power train. Luckily, my brother lost interest in this particular endeavor for now.
 
Originally Posted By: JTK
^ Some good reading for sure. Thank you. Opinions and experiences are all over the place with this power train. Luckily, my brother lost interest in this particular endeavor for now.


My prayers were answered...Amen
 
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