MidnightR6

Motor: 496 Mag

When I bought my boat, the previous owner told me that he had blocked off the top 3 holes on each side of the lower unit where it draws water in. He told me this was a common mod to prevent air from being sucked in while the trim is up. Has anyone ever heard of this?

I am asking because the last 2 times I have been out and only when I start to run the boat a little bit hard, I am getting a warning beep. I think the beep is because the engine is getting hot. When I back off throttle, the beep goes away and the temp gauge comes back down a little. Could this mod be preventing enough water from getting to my motor during these times?

compedgemarine

do you have a stardard lower or a dual water pickup lower. how high is the drive? usually you only plug the upper hole when you have a dual water pickup and a fairly high X deminsion as the upper hole will pick up air. plugging them with a standard housing could restrict the water flow enough if you dont have the lower pickup holes.

stlliberator

iTrader: (1)

Ya if you x demension is not raised you shouldnt have any need to block off the top three holes. My x is raised 3.5 inches, and I still dont have any of the holes blocked. You might be getting a beep due to heat, when is the last time you changed the impeller? Or it might be a oil issue. All depends on the beep..

Wes Burmark

Midnight, My Fountain came this way. The top several holes are blocked (the boat's in the water at the moment or I would give U the exact #). On the front of the torpedo there is a large opening to increase the flow. The torpedo part of the drive case was cast this way, this is not a modification I did. Check your lower unit to see if you have this. IF you do, then I am unsure of why you would be getting the warning beep and over heating unless your impeller is starting to weaken. Your 496 has the "closed" cooling system which I believe has a 170º thermostat. It should be easy to tell on your water temp gauge if you are overheating at WOT. I'm not sure if going to a 160º thermostat will cause mixture issues with your computer (someone on here will know - many VERY smart people to help us out) but that is an inexpensive option to give you a little margin of safety if it will work.

Good luck, Wes

Wes Burmark

I will take a picture of the low water pickup for you in the next week when I pull my boat out of the water.

Griff

Blocking the top few holes on a DWP lower is fairly common. It helps prevent air from being sucked in.

Wes Burmark

Here are the pix I promised (boat is back on the trailer). After I flush each engine with Salt-Away I back flush the drives for a minute each.