350 Mag Overheating

[dabeav3]

Have a 2006 Crownline 225 LPX with a 350 mag, captains call, with Bravo 1 with the 2 point quick drain that is overheating at idle. Have replaced the thermostat, impeller, engine water pump and finally the whole raw water pump. Starts up, temp rises to 180 and all seems fine. After a minute or two the temp starts to creep up. If I rev it up the temp comes down to around 150. Have hooked a hose directly to the raw water pump inlet with the same results so don't believe its in the outdrive. It has the power steering cooler which is clear and no engine oil cooler so don't believe there is blockage. Have seen a couple of posts which talk about not enough water is going to the engine and some 350 mags need a restrictor installed to force more water through the block. anyone know more about this restrictor or have any ideas? Thanks.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Is this a freshwater boat, or a saltwater boat,....

If run in the brine, pull the risers off the manifolds, 'n see how clogged up they are,.....

 

[Scott Danforth]

check for bravoitis

 

[dabeav3]

Been in fresh water and stored on the trailer all its life. Everyone talks about how great Mercs are but I've had a lot more problems than I did with my previous Volvo and OMC.

 

[alldodge]

2 point quick drain ... temp rises to 180 and all seems fine

Does the motor normally operate at 180 degrees?
If so is it closed cooled?

What is the motor serial number?

 

[dabeav3]

Correct the motor normally operates at 180. After idling it will start to climb. Give it some gas and it comes down to 150-160 again.OW630624.

 

[alldodge]

If you have open cooling you should have a 160 degree thermostat, and have a thermostat housing in like below (item 1)

http://www.mercruiserparts.com/bam/s...1750/11681/220

Give it some gas and it comes down to 150-160 again
Have hooked a hose directly to the raw water pump inlet with the same results so don't believe its in the outdrive

This leads to Bravoits as Scott mentioned. That said you also said it does this on a hose connected directly to the pump. There is no impeller in the drive if you have an Bravo drive (which you should).

The biggest issue is the single and 3 point drain systems. It all has to work correctly or there are issues. Here is your hose routing

http://www.mercruiserparts.com/bam/s...1750/11681/250

Here is the water distribution housing

http://www.mercruiserparts.com/bam/s...1750/11681/300

The issue is water must be restricted going to the exhaust elbows in order to keep the block full of water. The distribution housing should be closed off to restrict the water flow to keep the block full. There is also a Tee (item 20 in first link) which helps restrict water flow.

Get an inferred temp gun to measure temps around the block to see where the higher temps are

 

[rickasbury]

Interesting! I will follow this one.

 

[dabeav3]

In answer to your questions. It is a Bravo 1 with the engine driven raw water pump of which I have replaced the entire assembly. Have removed most of the water hoses and everything looks very clean. Saw a couple of posts which talk about installing a restrictor in one of the water lines in order to force more water thru the engine but couldn't find any specific details related to doing so. Out of curiousity I removed the outdrive lower unit and it is very clean as well. As you suggested it seems that the block is not getting enough water so when I rev it up it fills the block and the temp goes down. Put in a new Merc 160 degree thermostat some time ago with no help.

 

[alldodge]

The place where a restriction is needed with the 3 point drain is item 20 the Tee. The Tee either has restrictors installed or later versions are molded



With being able to rev motor and it cool down some also leads to bravoits as previously mentioned.



Your unable to just looking at where the hose connects to the transom to be able to tell, the hose fitting must be removed. The pic above is an extreme case

 

[QBhoy]

Hi
same exhausts as mine. Pull the exhaust rubber jointings off and check the diverter valve and bypass. Check the flappers going down to the leg too. Sometimes with these exhaust with the constant switching, the flappers get a hard time. They make a hell of a racket at the best of times with the corsa marine exhausts.

 

[dabeav3]

Thanks for the info guys. I will look at the tee as well as the exhaust flappers. I hope it is not Bravoitis as I think I would have to remove the engine to get to the connection. Every hose I have pulled has been very clean with no build up so I'll keep my fingers crossed.

 

[dabeav3]

Starting with the easy stuff first. Removed the hose from the tee. Hose is 3/4" ID with the tee being about 5/8" ID with no other restrictions. Any ideas on what size restrictor should be installed or what the restricted tee ID should be? If it is Bravoitis, would it be easier to just install a thru hull water intake rather than pulling the entire engine for access for a limited time fix? Have you tried just hooking up an auxiliary hose directly to the raw water intake hose therefor bypassing the outdrive and tossing it overboard to see if that helps identifying whether it has Bravoitis. Just no way I can get the transom fitting off to do a visual inspection without removing the engine. Thanks again, not much of my hair left between pulling it out and stress causing it to fall out.

 

[alldodge]

Hose is 3/4" ID with the tee being about 5/8" ID

Your tee fitting is the right size so don't think that's the issue

Don't see a thru hull fitting as an easy fix but I have not seen your boat. Mine was ruff to get at, but managed to do it.

As for using a hose over the side, I don't see that working very well. The pump has to suck water above the side, but once it did do this it might be OK, don't know. The other side of this issue, is you need hard walled hose 1.25 ID, other wise it could suck it closed. Also could only do this in neutral

 

[dabeav3]

So did your thru hull intake water mod take care of your problem? Would be a lot easier on my boat than removing the engine. I did hook up a hose directly to the raw water pump intake bypassing the outdrive with the same results. I know there is a difference between the volume the pump puts out versus the hose pressure but it makes me wonder. That's why I was hoping for the restrictor issue between exhaust and engine water supply. Also took the exhaust apart and the flappers and everything else look fine. If I could just get to the Bravoitis hose and see one way or the other it would make me feel much better. Don't mind spending the money it is the problem but have spent enought time and money already that was wasted. Do you know the difference between the sizes of the hoses/tee with and without the restrictor? Anyway its Monday and I thank you much for your help.

 

[alldodge]

Guess my comment of

Mine was ruff to get at, but managed to do it.

Might have lead you to believe I installed a thru hull, but I didn't. I managed to get to the transom fitting and remove the fitting which connects the transom hose to the engine pump.

You could use some short sections of clear hose to see if bubbles can be seen. If there is bubbles then trace back to were they stop.

The hoses on the tee should all be the same size, the tee creates the slight restriction

 

[dollar7499]

Hi Dabeav3, I removed my B3 outdrive (six nuts, pulled shaft out) and had Bravoitis to the extreme, but when I pulled the plastic fitting to check the hose in the inside transom assembly, it was squeaky clean. I suggest pulling the intake line from the raw water pump and sticking a hose in the line to see how much water makes it through your transom hose back to your outside bell housing.

I didn't see where you took your elbows off to see if they were clogged with scale, but you might have.

 

[dabeav3]

Sorry but have been gone for a couple of months. Took the outdrive off and inspected the hose installation which was as clean as the motor side.

To recap: Engine tends to overheat at cruise and at idle after extended run times. Have replaced the raw water pump housing/impeller assembly, engine water pump, and thermostat, Have back flushed the lines and installed a 1/2 inch restrictor in the hose leading to the exhaust manifolds before the tee with no help. Every hose and fitting I have removed has been very clean with no scale or build up. Things are better after the raw water assembly replaced but certainly not perfect. Engine has 320 hours and never been in salt water or stored in the lake.

 

[alldodge]

Clear hose to check for bubbles
Tee in a pressure gauge at the water pressure sender or other location (0-30)

 

[dabeav3]

More info. With extended idle the temp will sit around 180 and eventually start to climb from there. Rev it up and the temp goes back down to about 160. Also after cruising and coming to an idle it will put out a white/gray smoke out both pipes for 15-20 seconds. Take off again and the temp again goes from 180 to 160.