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Mercruiser 233 Overheating
Posted: April 16th, 2022, 10:03 pm
by Ctmangrum
My 1976 mercruiser 233 overheats at rpm when i run it with the plunger while its on the hard. Anyone else have that issue just when using the plunger? Just curious if its not getting enough water or if i have a more serious issue. Launching in 2 days so im committed. Thanks.
Re: Mercruiser 233 Overheating
Posted: April 16th, 2022, 10:03 pm
by Ctmangrum
Meant to say higher RPM
Re: Mercruiser 233 Overheating
Posted: April 17th, 2022, 9:02 am
by km1125
My guess is that you're not able to feed it with enough water to satisfy the flow at higher RPM. You really shouldn't running it "at RPM" on a hose.
How old are your impellers? When was the last time you inspected/replaced them?
Re: Mercruiser 233 Overheating
Posted: April 17th, 2022, 9:47 am
by Viper
RPM is the key here. It doesn't take much above idle on a garden hose for you to starve the pump. The true test is how it runs in the water. If we're talking inboard here, the pump can be serviced in the water if you find it still overheats at higher rpm after launch.
Re: Mercruiser 233 Overheating
Posted: April 17th, 2022, 12:06 pm
by Ctmangrum
km1125 wrote:Source of the post My guess is that you're not able to feed it with enough water to satisfy the flow at higher RPM. You really shouldn't running it "at RPM" on a hose.
Impellers are only a couple years old. Makes sense about the hose. Boat never had sea strainers so i wasn't sure what to expect. Appreciate it
How old are your impellers? When was the last time you inspected/replaced them?
Re: Mercruiser 233 Overheating
Posted: April 17th, 2022, 12:10 pm
by km1125
Just as a comparison, the average hose running wide open is about 10 gallons per min(GPM). A long hose or any restrictions will cut into that quite a bit.
At idle a small block raw water pump could pump 5-10 GPM but at 2000 to 3000 RPM that could rise to 40-60GPM. You could easily starve the pump supplying it with just a hose.