240 2006 sea Ray Sundeck overheats at low RPMS

johnsimeone · 2026-10-29T10:51:32-0600

I have a 240 SeaRay Sun deck from 2006. Recently the boat overheats at low RPMs usually at idle speed when let run for 10 minutes or more I have replaced the impeller and the raw water pump. I have inspected all the hoses for the thermostat and the power steering cooler. The boat ones is fine at 1000 RPM or more and only overheats when let idle for a period of time, anybody have any ideas?

alldodge · 2026-10-29T11:25:20-0600

Welcome
Your issue isn't a Sea Ray problem it's a motor problem. What is in your boat and we'll move the thread to that area. If you have a serial number that would be most helpful

johnsimeone · 2026-10-29T11:45:12-0600

alldodge said:
Welcome
Your issue isn't a Sea Ray problem it's a motor problem. What is in your boat and we'll move the thread to that area. If you have a serial number that would be most helpful

Thanks.its a Mercury Bravo III 5.0 engine. Serial number is OW384463

alldodge · 2026-10-29T11:51:30-0600

Moved to the Merc section and thanks for serial number

Looks like your motor can have open or closed cooling and if open can have 3 or 7 point drain system, can you clarify?

johnsimeone · 2026-10-29T12:20:43-0600

I’m not sure, but it is raw water cooled for sure.

johnsimeone · 2026-10-29T12:27:45-0600

3 drain

alldodge · 2026-10-29T13:30:21-0600

Ok THIS should be your motor

This is the open cooling system with 3 point drain

And this shows the check balls that are in the bottom of the exhaust manifolds

The check balls should remain closed when the motor is running, and open up when motor is off. They are used to drain water during winterization when the 3 point drains are opened. If check balls get stuck open they will let to much raw water go to the manifolds and out

Might also be your sucking air but finding out is harder than the 7 point drain. To find out if it's air, get a short piece or clear hose from the hardware store, a double barbed fitting and hose clamps. Disconnect the hose going into the water distribution housing on the front port side of the motor. Install piece of clear hose and run motor at idle and look for bubbles

johnsimeone · 2026-10-29T14:12:15-0600

And what does seeing (or not seeing) bubbles indicate?

alldodge · 2026-10-29T14:20:12-0600

johnsimeone said:
And what does seeing (or not seeing) bubbles indicate?

With boat in the water and not on a hose there should be no bubbles. Seeing bubbles means the impeller is cavitating or there is a hose or connection allowing air to be sucked in. You get air means less water, less water and things get hotter

johnsimeone · 2026-10-29T14:35:27-0600

Understood. So to test this the boat needs to be in the water?

alldodge · 2026-10-29T15:00:20-0600

johnsimeone said:
Understood. So to test this the boat needs to be in the water?

You said it over heats if it idles for a while, I'm assuming you in the water because you also said it doesn't if your above 1000 rpms.

We can only work with what you tell us

So does it over heat on a hose?

johnsimeone · 2026-10-29T15:08:13-0600

Yes/ it overheats on the hose as well.

alldodge · 2026-10-29T15:09:35-0600

Post a few pics of your motor

johnsimeone · 2026-10-29T15:36:40-0600

Bt Doctur · 2026-10-29T15:44:06-0600

Could be a early case of "Bravoitis"

johnsimeone · 2026-10-29T15:45:08-0600

Bt Doctur said:
Could be a early case of "Bravoitis"

?

johnsimeone · 2026-10-29T17:09:08-0600

alldodge said:
Ok THIS should be your motor

This is the open cooling system with 3 point drain
View attachment 420774

And this shows the check balls that are in the bottom of the exhaust manifolds
View attachment 420775

The check balls should remain closed when the motor is running, and open up when motor is off. They are used to drain water during winterization when the 3 point drains are opened. If check balls get stuck open they will let to much raw water go to the manifolds and out

Might also be your sucking air but finding out is harder than the 7 point drain. To find out if it's air, get a short piece or clear hose from the hardware store, a double barbed fitting and hose clamps. Disconnect the hose going into the water distribution housing on the front port side of the motor. Install piece of clear hose and run motor at idle and look for bubbles

Just found out from my mechanic that we already replaced the check ball assemblies

240 2006 sea Ray Sundeck overheats at low RPMS

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

alldodge

Moderator

johnsimeone

Cadet

Attachments

Bt Doctur

Supreme Mariner

johnsimeone

Cadet

johnsimeone

Cadet

Follow Us