496 Hydrolock

Ki
Tomco said:
An update in case anyone else has this problem and follows the thread.

Installed the missing exhaust shutters and that seems to have fixed the problem. Ran the boat on several higher speed runs, pulled the plugs on the offending side and they were dry and burning nicely. We went on a 4 day trip, with several sections on plane and then at idle speed into the locks - no problem. It is not an expensive part (less than $100 for two) and easy to install.
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That's good to know, I think should do the same. I haven't had a problem since but you never know, if it happened once it could happen again. Did your other engine have the shutters? Can you post the part numbers for the shutters?
 
Last edited:
Sorry for not commenting sooner on this one, I just saw it this am. When we had the transom assembly replaced three years ago we also discovered there were no shutter valves in the Y pipe. As everything was coming out for the replacement of the transom assembly it was easy to determine that the shutter valves had never been installed. The service manager called Mercruiser and after a little digging discovered that Sea Ray had spec'd the engine package that way.

I do know from the previous owner's records that shortly after he bought the boat Sea Ray/Merc ran a recall program to replace the risers with taller ones. I also recall hearing at one point that Merc had also raised the idle rpm spec to keep positive pressure in the exhaust system at all times.

Henry


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Tom - glad to hear that resolved the issue. If you haven't, I would also make sure the other engine has the flappers.

I would be curious to know the reasoning behind leaving the shutters out. All I can think is they were trying to reduce back pressure in the exhaust. I think newer engines over 300hp have exhaust tubes instead of exhaust bellows. I know I just replaced my bellows and went with the tube, I'm seeing another 50-100rpm at WOT.
 
Jeremygavin said:
Ki

That's good to know, I think should do the same. I haven't had a problem since but you never know, if it happened once it could happen again. Did your other engine have the shutters? Can you post the part numbers for the shutters?
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Jeremy, I had the marina order the parts. I have asked the Service Manager for the number and will post it when it arrives. I haven't checked the other engine yet - it is working fine but I do plan to take a look.

Henry, we suspected that the shutters were never installed but when the mechanic went to install the new ones he found the rubber end of the shutters still in the slot in the exhaust tube. He is thinking that they were there at one time ... I'm not real sure if it was or was not! Additionally, when I spoke to the Mercury tech he did say that there is a minimum of 13" required between the exhaust shutter and the top of the riser - more is better. I measures mine on the weekend and have close to 16", so i don't plan to add the extensions.
 
Shutter part number was: #80166A1
 
Tomco said:
Shutter part number was: #80166A1
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Great, thanks for the info. I have dealer looking into it as well buy have not heard back from them yet.
 
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