Merc 1075 Overheating
 

My stbd engine is overheating in high RPM only. In Idle its fine it could run all day at about 150. I just replaced all 3 impellers in the raw water pump and im getting great water pressure but it still gets hot when running hard. I'm guesssing I probably have some seaweed or sand that passed through the strainers. Anyone experienced this and had good results?

Maybe backflushing the system? Possibly inside the oil cooler? What would be the easiest way to backflush the system where to start and finish? Or any other suggestions.

One this engine, did you manage to destroy the impeller or did you just change it due to the over heat problem? Do you have water pressure gauges? It definetly sounds like a restriction issue... oil cooler is where I would look especially if you lost an impeller... Good Luck

Todd

Does that motor have a power steering cooler?

teamsynergy,
No the impeller came out perfect they were just already bent to position and getting hard when inspected also stamped 08'. I have smartcraft vessel view race edition and analog gauges water preassure is even on both engines at high RPM I beleave somehwere in the rage of 20-25psi. To flush the oil cooler do I need to pull the raw water pump out to get to the inlet hose or is there an easier way?

JoeD,
Not sure on the power steering cooler I dont think it does.

if you have equal water pressure and the overheating is at high RPM sounds like it's leaning out driving temps up..

If your engines were working fine before you changed the water pump impellers, then you may have torn and broke off your new ones. Sometimes it takes a while to prime your water pump after new impellers are installed. If this is not done correctly, you can destory your new impellers. After you changed your impellers, did you start your engines in the water for the first time or on the trailer with a water hose. Hopefully you have a seperate water hose connection on your boat and you do not have to rely on those water clamps that attach to your stern drive. If you started up your motor in the water for the first time and left it at idle, you may not had enough RPM to prime your water pump. Result is broken impeller blades.

The Mercury maintence book that came with your engines gives you step by step procedures for flushing coolers. That seagrass is a ***** !!

Might check the seals on your strainers too. If the rubber gasket around the top is not sealing properly, you can pull air into the system which reduces cooling efficiency. At low RPM's the suction from the raw water pumps isn't much so it stays cool, but at higher RPM's those pumps really start sucking and could be pulling air in. Just another thought.

In the maintenance manual it shows how to clean the transmission/ power steering cooler. Could this be part of the over heat or just the oil coolers. I just got my service manual for my engines and it looks like I would have to drain the oil in the lines and bellhousing to access the oil coolers. Any one can help bbefore I go on this mission and find out I didnt have to. In the trouble shooting guide it says to check charge air cooler for foreign material, would I have to pull off superchargers to get to that cooler? Also I checked the seals around strainers and there perfect. Its annoying I can run the boat all day as long as I dont push it hard. I know it has to have some seaweed its running around 10-12 degrees hotter than the other at any given speed.

A couple of other possibilities, are you pulling water thru the outdrives? I had a similiar overheat, caused by the hose fitting on the intermediated housing. It became corroded with salt around the inside of the fitting , causing the hose to close down, to approximately 1/8 of an inch , no problem at idle but once up above 3500 temp starts to creep up. Could not figure it out until I was hanging off of the transome and noticed I was getting less water out of the exhaust, from the motor that was running hot.
Are your guages both accurate?
Good luck post your findings, so we all know what the cause was.

Big Boys Toys,
No I have #6 drives my pickups are on the transom on my Nortech Cat. Yet to pull off any coolers hopefully this week I can get to it and let you guys know unless anyone else has a solution

nsxpert, I'm having the exact same problem with my starboard motor. Have you resolved your problem? What was the problem?

Tsunami LC,
I noticed my water pump was leaking thru the wheep hole in the front so I rebuilt the pump hoping it was airating and overheating. Took her out this weekend and it ran fin never really pushed it past 110 but still noticed the temp was like 5-8 degrees warmer. Not 100% sure it it solved my problem. Hoping I can figure it out before the Keywest poker run in a few weeks. If you find anything else as the culpret with yours let me know.

nsxpert,
I have my boat out for the winter with other projects (paint, drives, etc), but I will let you know what if anything I find when I run it again in the spring. Thanks and good luck in Key West

Could this be running lean? I am not very familiar with these engines but I do allot with turbocharged and N/A car engines.

Many times when we see a part throttle over heating issue it ends up being a lean spot in the throttle posistion. That can account for highway overheating at a set RPM like 3500 where it doesnt over heat if it stays under 3000 etc.

Do you have O2 sensors of anykind on it?

Just a tip I always pack my impellers with vasaline or something that will lubricate them for a few minutes while they prime it will also creat more suction with the better seal which can help prime them better in the first place.

anyone else do that?

:eek::eek::eek: No, I was always told petroleum jelly causes a shorter life span.

I use non petroleum lube found at most pool stores for pool orings http://www.intheswim.com/Pool-Equipm...mula-327-Lube/

Do you have harden marine sea stainers? And PSI blow off valves? Some times the valves go bad or get crap in them and then let airation happen. We will be going to KW and be down in S Florida before the poker run. Let us know if you need any assistance.

856 425 1474

Soap works well also. Standard liquid dish soap.

I dont leave it in there and I have taken it apart after 1 day out before and there was no trace of the vaseline so I am not sure theres any differnce but good info just in case.


I have been doing this for many many years with no ill effects so far.

I will look into that further

Dish soap here as well.

PIT ,
I do have the Hardin marine strainers, I checked my seal and its in good shape so no air getting in thru there. Not sure where the PSI blowoff valve is? That could be the issue cuz I tried to backflush some hoses and didnt find anything. When will you be in MIA?