New 8.1 496 Engine overheating!

Last fall I bought a 2018 8.1 496 Ho engine from authorized Mercury dealer. The ad said that someone installed it in a boat and used it for 1 hour and decided to upgrade to a larger engine. They removed it, flushed it with fresh water and put it back in the factory crate.

They replaced the fuel filters, changed the engine oil/filter, and water pump impeller. Since it was never warranty registered it carries a 1 year warranty and is certified pre owned.

I had engine installed and started it at the shop and it ran perfectly and sounded great. I just put the boat in last week and ran it 1/4 mile (5 mph) and saw the temp rise and alarm go off. I called my mechanic who came to look at it and the thermostat had a gelled anti freeze on it. In testing it at the dock he is not hearing water spin when he's circulating the water and when he throttled the engine he said it should have shot water out.

He changed the thermostat and it's not circulating water. He took the belt off and spun it by hand. Took the hose off that goes to the throttle and spun it. It's not moving anti freeze at all so he believes it's the water pump. He said he knows for a fact that when you spin the water pump it should be moving anti freeze. Also he was reviving it and the manifold and elbows were cold at 80 degrees so it's getting plenty of salt water in.

My mechanic has been working on engines for over 30 years but it's the first time he installed this particular one. Just wondering if there's anything else that it can be and is there reason to be concerned about this engine? My mechanic mentioned that it had been sitting for 4 years but I didn't think it would be an issue since filter and impeller were changed and stored in crate. Not only that it's certified pre owned with a warranty. Having Mercruiser repair it is another issue (availability in Rhode Island during boating season) so I believe that my mechanic will need to.

Any ideas or help would be appreciated!

Thanks,

Scott

Sounds like you're doing all you can. Too bad your first go was a disappointment, but at least you caught it early.

o2batsea said:

Sounds like you're doing all you can. Too bad your first go was a disappointment, but at least you caught it early.

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Thanks Im trying. Do you think theres anything else that it could be besides the water pump?

My only question is how long the new impeller was in there. Did they do it just before handing it over to you or 4 years ago?

o2batsea said:

My only question is how long the new impeller was in there. Did they do it just before handing it over to you or 4 years ago?

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I was trying to find out that same question but they haven't gotten back to me. Also per Mercruiser when something is certified pre owned it supposed to be throughly inspected as new and usually under 10 hours. I wouldnt think Mercruiser would want to warranty something that is likely to have issues and end up costing them in the long run. The downside to the warranty is the waiting period though.