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Blown merc 470 4 cylinder


ReelWork

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Yeah fresh oil change and new coolant... Had it out other day and the water pump quit on lower unit and over heated about 220.. Changed the water pump and took back out ran good at first then started knocking bad

Captain1466

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from experience from having the same issues sounds like number 4 cylinder is knocking . they are known to have the connecting rod lock up . I replace mine with another 3.7 xl and kept the original motor for parts . I got lucky and found a good motor in a crush boat the owner wanted it gone got it cheap . good luck with repair

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Def. Sounds like a rod knock. Pull it and get a bearing kit and piston ring kit. Have the crank turned or replaced. You'll have less money in it than another motor and you'll know what you have!

Sent from my XT1080 using Lake Ontario United mobile app

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Def. Sounds like a rod knock. Pull it and get a bearing kit and piston ring kit. Have the crank turned or replaced. You'll have less money in it than another motor and you'll know what you have!

Sent from my XT1080 using Lake Ontario United mobile app

X2

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Who does that kind of work around here? I can fix some things but never messed with a motor. I would do more damage than good lol.. Motor was just rebuilt in 2012 and I go out and overheat and she throws a rod wtf!

Captain1466

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Yeah kind of weird it overheated and throws a rod bearing. 220 isn't overheating by a lot most engines run around 200 I would have thought warped head or something. I have a feeling that the rod bearing was already on its way out. Did you own the boat when it was rebuilt the first time? What happened that it needed to be rebuilt?

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I'm still leaning towards a tight wrist pin, 200* isn't motor destroying hot, but if wrist pin was a little tight and she got that hot it could have wiped out the rod bearing. I'd pull the motor, the head and the crank. Like LakeBound said get the crank turned inspect Pistons for a tight wrist pin, they should have no resistance, a wrist pin kit, and insist on Clevite rod & crank bearings. The best bearings, used in the racing world, these marine engines get used hard they are all about making power, and turning rpm's way higher than a automobile engines for longer periods of time. If not doing this yourself at least use the info suggested. That way the shop or whoever gets this prodject doesn't try to snowball ya!! Best of luck.

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The boat normally ran about 130 but went to make a run to a new spot and bam temp jumped up to 180 then spiked out to 220 at one point I think my buddy said it was at 260 and we shut her down to cool.. Tried calling people for tow in but had to limp her back to launch.

Captain1466

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a 3.7 L merc is a aluminium block and a 460 big block head . they do not stand up to a over heat . I would bet its a frozen wrist pin .  dark water is right barrettes all the way fran been with mercury a long time , bring a fat check book tho

Edited by fisherdude
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I researched these motors pretty extensively as we were going to buy a grady i/o with the 460. Good little motor but x2 with what fisherdude said. Heat is the enemy of this engine. Some say that high quality lubricant is important with this power plant too But that of course is opinion. Good luck with your repairs. Hope you are back in action soon.

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 There is one in Canindagua sp ,asking 695.00 was listed on Craigslist Buffalo might be in other areas on CL ,in Boat Parts section. I would go that route before dropping 1500 + for a rebuild. The outdrive water impellers should be religiously changed every two years on those motors. As noted ,aluminum head on cast iron block plus overheating that setup is a disaster waiting to happen. Probaly get it for 550-6 at the most.

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Upon further review I looked it up in Buffalo and it auto searched other areas , so it might be in the Finger Lakes /Syracuse/Rochester listings. If possible you want to run a 4" heat exchanger. They are good motors but cant take overheating like a complete cast iron engine. Convert the points as well to a petronix system if not done already,well worth the 125.00 to be done with points.

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