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2005 BF225 Overheating at idle

I

im2fast4you33

New member
Hey guys, got kind of a weird issue here.

Bought motor and have it on a stand, wanted to he comfortable with it before I slap it on the back of my boat.

So here goes...

The engine starts up great, but throws the overheat alarm after maybe 2 minutes. Solid continuous beep, no pauses, with the red light on for overheat. Im submerging the lower unit in a tub, about an inch above the intakes

Here are the things I've done...

1. Changed the water pump, looked OK, not great. No fins missing

2. Checked thermostats, they are corroded (green) but open in a pot of water.

3. Ran without thermostats, still overheats.

4. Put thermostat in one head, and left thermostat out in head with the water pressure jacket, pulled hose off of manifold to see of water would flow out of the block. While idling, it does not, but if I rev the engine, it will start to come out. Is this normal?? I would think water should flow out of the thermostat at all times once open (or in this case, removed)


So one thing that's odd here. If you rev the engine some, and don't just let it idle, it won't always overheat. At one point had it running like this, and after maybe 10 minutes it did overheat.

I cycled the motor on 3 times. First 2 alarm came on right away, 3rd time no alarm and ran another 20 minutes. That has me at a loss.

I'm pretty confident I'm overheating, the manifold burns to the touch when the alarm is going off.

Witness seems strong.

What do you guys think?
 
1" above the intakes is nowhere near deep enough. You need to have it submerged at least 4 " above the cavitation plate for the pump to prime and pump water effectively.
 
Good advice above, if that doesn’t work, do a major vinegar or other flush with a cleaner. Replace green thermostats, they are on their way out if already green from rust. A major vinegar flush is at least 4 large jugs of vinegar in a barrel, fill barrel with water, run at 1500-2000 rpm until vinegar/water gets quite hot.
 
Suggest you drop lower unit and slide a hose, can get correct size hose and garden hose attachment from hardware store, hose has have a snug fit over the water pipe and connect to garden hose, turn on faucet and run the engine. If it overheats then there is something definitely going on with the engine and not with the impeller developing cooling pressure in the block. engine not running pull thermostats one at a time and see if water will flow out with hose flowing water. I have seen on the 150s where cooling water is not making it out of the thermostat. If water does flow out then some kind of vinegar or barnacle buster flush might help. But if water isn't flowing out then you might have a open poppet valve or corrosion hole. Check under/behind VST and look for any water coming out of the block this is a location that I have seen Honda V6 outboard engines corrode thru and loose cooling water.
 
Hey guys, so good update..

With lower off, i bought 3 gallons of 30% vinegar with Mayne 2 gallons of water. Tied a bilge pump directly to water intake pipe and flushed for about 2 hours. Making sure all water went back into tub, with thermostats out.

No leaks at all top side, so that's good news.

After 2 hours, saw alot of cloudy gunk. I decided to run the motor to temp, took about 10 minutes, which was good news.
After getting to temp I tapped lightly on the manifold with a hammer to get anything lose.

After I was done, that water was BROWN. I'll take a picture when it settles.

Bolted lower back on, dunked in a barrel I found that I can shove the whole leg into.

Runs like a champ and pisses like a racehorse, no overheats.

Thanks everyone. Looks like I needed a good flush and deeper water!
 
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