Mercruiser 165 vs GM250 automotive?

Discussion in 'Gas Engines' started by Danielsan, Aug 6, 2021.

  1. Danielsan
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    Danielsan Amateur designer-builder?

    What about the Merc 470 is a 170hp 4 in line, where did they get the same performance as the 165?
     
  2. ondarvr
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    ondarvr Senior Member

    The 470 is not considered a desirable engine for multiple reasons. So don't go that route.
     
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  3. Danielsan
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    Danielsan Amateur designer-builder?

    OK i trust your opinion, for my general interest why?
     
  4. gonzo
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    gonzo Senior Member

    The main problem was the interface between the aluminum block and the cast iron head. If you find one in good condition and fill it with modern antifreeze they are fine. The other issue is that they use an outboard motor charging system that is not very good. The solution is to install an alternator. They sell a kit for it.
     
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  5. Danielsan
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    Danielsan Amateur designer-builder?

    ok nice to know.... wondering why it had more hp than the straight 6 for same technology of engine... les torque for sure....
     
  6. gonzo
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    gonzo Senior Member

    The heads, pistons and rods are out of a Ford 460.
     
  7. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Interesting discussion. My 1972 Sea Ray has the Mercruiser 165. The inline 6 which is the GM 250. Basically they are the same engine. GM made millions of them and put them in pickup trucks for about 20 years. Mercury simply borrowed the blocks and added marine parts. They do have stronger pistons and rods, and valves. But the cam shaft may be the same as the truck cam. I have heard people say it is and others say it isn't. But most of the stuff that hangs off the block are the marinized parts. The water pump uses a slightly higher volume impeller and the impeller is bronze. The previous owner of my boat had an auto impeller in it and it was a pile of rust. The exhaust manifold is made for marine use with a water lift. I got a new manifold and lift made by Barr from an online source. Of course, some had raw water cooling and others had a heat exchanger. The 72 engine in mine was raw water cooled. It died at 47 years old and I replaced it with a 1978 version, from another boat, and that engine has a heat exchanger. The parts are readily available in the US. I have never had a problem finding replacement parts. However, I did change the distributor to an electronic breaker less system and it improved the performance and reliability immediately. Anyway If you need a list of sources I would be happy to put one together. Of course it will cost a lot more to get it from the US. But I don't know sources in Europe. By the way, what has been said before is true, if the rust is just surface rust then the internal parts are probably fine. My boat sat for ten years out in the rain and wet (it rains a bit here) before I bought it, and the engine ran fine after I cleaned it up and replaced a few parts. It still had good compression. It ran for another ten years until the water passages in the head rusted out. But 47 years is not too bad.

    PS: I might add, mine has a Rochester carburetor. Those carbs are readily available from online stores. They are remanufactured and they are marine versions. I don't know if they used Rochesters on engines delivered to Europe but if they did the rebuild kits are available, as well as new Carburetors.

    BTW forget the 470. They are notoriously bad. And if you decide to go to a V8 or an engine with more horsepower and torque you would probably also have to upgrade the sterndrive.
     
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  8. powerabout
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    powerabout Senior Member

    I have never seen a volvo with an inline chev, the inlines were always volvo engines.
     
  9. powerabout
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    powerabout Senior Member

    I would go chev v6 to replace a inline 6, better chance to find one as Volvo used them as well.
     
  10. gonzo
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    gonzo Senior Member

    The 4.3 GM is an easy engine to find. They made millions of them.
     
  11. Danielsan
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    Danielsan Amateur designer-builder?

    Thx for all the comments and advice, I know it seems silly these days to keep hold on these gas slurping engines but i want to bring the small boat project to it's end. Close to me I just found a reman 250 all complete with drive for 2.5k€ the guy had it overdone in a shop because its boat sunk... after reman the engine was in his garage for few years and recently the hull got severe damage after a storm so the guy decided to let the engine go. after reman he filled it up completely with oil so it would stay oiled. All I will have to do is spin it a few times manually, drain the oil, it put new oil in. check the valve clearance, the ignition, prime the oil circuit, cross my fingers and fire it up without the spark plugs to check compression first and then fire it up for real . It came with many spare like alternator, starter exhaust manifold, carb,.... maybe to be sure i could have a camera inspect into the cylinders to be sure all looks ok.....
     
    Last edited: Aug 26, 2021

  12. baeckmo
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    baeckmo Hydrodynamics

    Sounds fair enough, good luck!
     
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