www.iFourWinns.com

Replaced the impeller end of year, had the dealer winterize. Put her in on the trailer ran for about 5 minutes and the temp started rising quickly. Shut it down when the guage went over the midway point. Let it cool and installed another new impeller. Runs cool now but there is a terrible knocking noise. The noise only happens under a load (in gear) If you take it up to 2500-3000 rpm in neutral rev it is smooth as silk. The oil is crystal clear, didnt even harm the exhaust baffles but the dealer seems to think it overheated enough to warp a connecting rod, I dont see that this is possible without damage to the exhaust baffles or scorching the oil. It didnt even run for over 5 minutes??? Any ideas? 5.7 Volvo/Penta SX

I wouldn't judge the situation by what DIDN'T happen -- but by what did happen. It sounds to me like the oil got hot enough to thin and you lost a rod/main bearing --

It is surprising that the small overheat you describe would cause this, I have done that and much more to a Mercruiser 5.0 and a 5.7 more than once in the last 20 years I owned those without any KNOCK developing.
(but not to my Volvo 5.7) Given that, there is no doubt it could happen.

I might suggest a second opinion -- if you are that doubtful -- or just want to be that certain before spending money -- but to me the dealer certainly could be correct and probably is.

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DaleG -- West Palm Beach FL
2003 240Horizon -- 5.7Gi -Duoprop

Im going to say that the knocking is just a coincidence and its your u-joints or gimble bearing that sat all winter, the grease dried out, and now the U-joints are "complaining".
If you say your exhaust baffles are still ok, your oil wasnt "burnt" as in it smells burned up, and your temp gauge only went slightly past 1/2 way (which isnt the 1/2 way mark 160F anyways?) then I cannot possible conceive any internal engine damage.
Get the opinion of another marine mechanic, one that is experienced with Volvo.

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1997 Four Winns Vista 278
T - 4.3l EFI
Kohler 4esz Genset
379 hours as of 8/8/21

I still havent heard anything from the dealer, I just find it hard to believe it is a problem with the lower engine, It did overheat once before and I melted a baffle and that was it, since then I have been extremely cautious and at the first sign of overheating I shut it down and checked the water pump. Ill let you know when the dealer gives me a definate answer. Does it really matter if it is a merc or a volvo dont they both use Chevy or Ford engines? It shouldnt matter what out drive it has right!

I'm not a motor head, but if it's a physical defect from the overheat such as what the dealer suggests, shouldn't the noise be heard wether the engine is under load or not, aren;t the rod still pushin'?

Just a thought, did you check the gearlube in the outdrive? Could they have forgotten to refill it? I've seen stupid stuff happen all the time!

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Jvalich
http://www.badcock.com

'04 FW 288 Vista "Mental Floss"

gimbal bearing

Could be a gimbal but the gimbal spins in or out of gear, as does the universals.

_________________
Jvalich
http://www.badcock.com

'04 FW 288 Vista "Mental Floss"