1075 overheating
 

Hey guys,

would appreciate any help on this matter.

1075 running good at 65, 70 mph. When I start trimming the boat out I’m getting overheating on the starboard engine and it’s being thrown in guardian.

i have rebuilt the pumps, gone through the complete cooling system and all is well.

water pressure is 18 to 23 psi.

thanks

is this something new?and where do you boat?

I live overseas.

i bought the boat from the us and have been having this issue.

can you post a pic of your water pick ups.what area of the US was the bought from.I'm suspecting corrosion in the water path around the bell housing may be the problem.

miami

attached picture of water pick up. I have gone through everything. My mechanic wants to adjust the pick ups next as he believes due the water density here it’s not biting hard enough


https://cimg8.ibsrv.net/gimg/www.off...bbbaa7e77b.png

Is there enough hose length to swap the inlet hoses from side to side ( at the transom) and see if the problem switches to the other side?

i do not believe so

does this boat have 1 sea strainer.as for the water pick ups,,someone was working on them for more water,,can see the welding.I'd put a groove(more like a triangle groove) in the bottom of the boat in line w/ the water pick ups.if non of these tricks don't work.time to pull the heads,they're probably rotted.
if you have 1 sea strainer,try adding a second one.

Each pick up has its own strainer.

i don’t believe the heads are rotten. I was told the engine was rebuilt 15 hours ago. I have bought it from a very reputable person.

well,go after the thermostat,,let me guess,seller said it never ran hot for him.

Swapped thermostat and still.

You said you went through the cooling system so you back flushed all the hoses and stuck your finger in the end of the oil cooler and felt around for debris? As mentioned above, you should get enough hose to swap pickups between the engines at the transom. Did they rebuild the one engine or both?

I have still not found the problem.

i have gone with a heat gun during a run.

When I put the heat gun on the thermostat housing prior to the thermostat I’m getting 195. After the thermostat around 160.

i have changed strainers, hoses, and gone through the whole cooling system.

would anyone recommend where I look next?

thanks

Post some Pictures front , back, sides and tops of your engine . I would think it has an oil cooler. Replacing it would be a good place to start.

Chris

I’ve cleaned it out. I do not believe that is the problem

There were others back in 2010 with the same problem here on oso. "Merc 1075 Overheating"

Yes I went through all those topics but I’ve done everything that they recommended in them. I am yet to find the culprit

Did you switch the pick-ups with longer hose?

What are the guages reading for temps?

When you follow the raw water path from inlet to outlet...does the temp/flow change from the good engine?

You sure you are overheating and it’s not just a bad guage or sensor?

I had a friend with a similiar problem on a 500EFI.
Chased the problem forever , turned out the salty, rusted block and cooling passages were blocked.
You got it from Miami,it`s probably salty . Is the "reputable" builder Randy from Cobra?

no it isn’t cobra.

I’ve back flushed the block through flow was ok

Open up the Trans cooler. Has a small cover on the end 9/16 bolt. Its the first cooler after the pump. They can get clogged there with sea grass. Happens a lot. Also you really should be running 25-35 psi of water pressure in a 1075. I usually change the thermostat to140 deg on all the rebuilds.

As both headers were not the same I went as far as swapping the motors to see if it was in the headers/tails.

i can confirm it is in one of them as the side (different engine) is now overheating

Does anyone know how I can unclog the tailpipe
or header?

thanks

Take the headers off and back flush them to start

fill the pipes with muriatic acid for a few minutes then flush out with water.don't be surprised if you have pin hole leaks.

I do think you're onto something, but your water pressure around 20PSI seems pretty low. I'm pretty sure on the 1075's, the water pressure sender is located in the port side of the bellhousing, which is before it enters the block. So, in that case, I would assume any blockage in the block or headers would be causing high water pressure, not low water pressure.

Why do you switch to the 140? Are the 1075 thermostats just standard BBC 140 stats like they sell at Hardin?

Yes high flow 140 deg thermostat.

So just and update on this…

I have replaced the tails on the engine as I found a leak in them. The engine is still overheating.

i have taken off the headers as that’s all that’s left. I have found one is leaking but it is not a major leak.

i do not know if that would cause my issue

I don’t think leaky headers would cause an overheat…

your gonna have to take the heads off and have a look.

no.

i have swapped engines and overheating is on the starboard side still with the port engine. I could not swap the headers due to different sizes

Make sure the bypass hoses off the thermostat housing has the water restrictors or a downsized barb fitting inside. Its the hose going to the mid section of the header not the lower water rail of the header. If you have to much water flow there the engine will start to overheat past 4k rpm. Also open up the transmission cooler to confirm there is no sea grass clogged.

im not aware of these water restrictors Would you be able to provide a pic or a link of it?

thanks

doesn’t that mean your problem exists between the water pickup and inlet to engine? Unless I mis-understood

i suppose you could also have a restriction in your headers?

I have swapped those two and removed the ball valve and ran a straight line to test.

the overheating is coming as you gain speed.

over 3k rpm

i am now going through the headers. One has a slight leak and one does not.

I have swapped those two and removed the ball valve and ran a straight line to test.

the overheating is coming as you gain speed.

over 3k rpm

i am now going through the headers. One has a slight leak and one does not.

Dave Wesseldyk has rebuilt many Merc 1075's over the years and he's excellent at trouble shooting the 1075 with trouble codes, etc as the engines sit in the boat.

I've seen several customers bring their boats to Dave's shop with these 1075 engines and he fixes them.

I don't know how much he can help you over the phone, but you can try calling him.
616-308-5119 Wesco Marine in Jenison, Michigan.