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  1. #1
    Join Date
    Oct 2019
    Posts
    1

    Default Mercruiser 4.5L 250hp engine on a 25ft 2007 Crownline 252EX

    I own a 2007 Crownline 252EX bow rider with a Mercruiser 350 MAG engine.

    The engine is dead and needs to be replaced.

    I need some advice on my options regarding the replacement. Keep in mind, I live in Hong Kong and donít have the luxury of having many options.

    Supposedly I have 2 options, get the equivalent new 6.2L 300hp engine by Mercruiser, or perhaps the 4.5L 250hp engine.

    I mostly use the boat for pleasure trips to local beaches etc, I donít use it to wakeboard or the like. I drive in open sea between the small islands, so donít particularly get flat conditions. I typically donít push the engine hard, usually drive at between 2500-3500RPM....hard to exceed that depending on sea conditions.

    I am leaning towards the 4.5L engine, because I donít feel I need the power and prefer (or hope) that I can run it without burning a ton of fuel (which my current one does). My boat has a dry weight of 5100lb and is 25ft long. My concern is this may be too heavy for this engine, but I do see that Searay do sell their SDX250 with that engine and it has a dry weight of 5300lb with similar size.

    Looking for any help or input here. Would be greatly appreciated.

    Another point to note, the 4.5L is in stock, the 6.2L will need to be shipped and will supposedly take at least 3 months. Have to say this definitely is factoring in to the equation.

    Thanks for reading and hopefully can get some replies.

  2. #2
    Join Date
    Dec 2001
    Location
    north ayrshire
    Posts
    461

    Default Re: Mercruiser 4.5L 250hp engine on a 25ft 2007 Crownline 252EX

    Why not replace with a like for like long block engine, probably cheaper, less electronics to go wrong & you know it works with the boat.
    Modern technology isnt always a good thing

  3. #3
    Join Date
    Jun 2005
    Posts
    314

    Default Re: Mercruiser 4.5L 250hp engine on a 25ft 2007 Crownline 252EX

    How badly damaged is the original engine?
    Can you not have it repaired?

  4. #4
    Join Date
    Dec 2001
    Location
    north ayrshire
    Posts
    461

    Default Re: Mercruiser 4.5L 250hp engine on a 25ft 2007 Crownline 252EX

    New 5.7v8s available here:-
    https://repowermarine.com/index.php/...ngine-567.html

    Edit:- hadnt noticed the Hong Kong location, the link above is probably no use but given the popularity of the small block chevy id be surprised if there wasn't a supplier that could supply a direct replacement.
    The downside of going with a mercury manufactured engine is there will be no source of parts outside the dealer network & probably no diagnostic support either. Both would be a cost concern for me
    Last edited by Beamishken; 09-10-19 at 07:42.

  5. #5
    Join Date
    Mar 2016
    Posts
    1,016

    Default Re: Mercruiser 4.5L 250hp engine on a 25ft 2007 Crownline 252EX

    Hi
    I can say with some confidence you should perhaps avoid the 4.5 in that boat. Couple of reasons.
    It really wonít have the guts or torque to get you on plane comfortably. It will be really stressed doing it too.
    Apart from that...Iím going to take a guess that your 350 mpi on that boat will be coupled to a bravo or bravo three drive ?? If so you have further issues to deal with going to a 4.5. May be wrong but I think they are usually only used on an alpha one. The alpha has the water pump in the drive. If you have a bravo...it will be driven off the engine. Youíll need to figure that one out on the 4.5.
    For my money...Iíd be ordering another 350 crate engine and using your existing mpi running gear etc to put onto the new crate Marine 350.
    Iím not certain but if you go to the mercury made new 4.5 or 6.2...the engine mounts you have glassed into the engine bay may need changed too. Perhaps they are the same, but your current engine is a GM v series and the new mercury 4.5 and 6.2 are made in house at mercury now. Good chance they are different.
    Even if your 350 is coupled to an alpha...you may need a serious ratio change or at least a really serious prop change too.
    Just my tuppence worth !

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