Intermittent overheat alarm 225 honda

I have a 2006 225hp outboard with about 1400 hours. A few days ago, about 30 minutes after starting my trip, the alarm goes off, and the red overheat light lights up. I was going at idle speed. I shut off the engine then restarted it and it was perfect for another 15 minutes. This time I was going about 3,000 rpm and when the alarm and light went on, the engine slowed down. I slowed down and the light and alarm went off by itself after about 5 seconds without me stopping the engine.
I went back to the dock and changed the 02 sensor.. (I had to change that a few times and it was similar symptoms but with the check engine light instead of overheat.) I think it helped... I got about 40 minutes out without a problem and it happened again. I shut it down, restarted and was fine to get home.

The engine is peeing -but this engine's pee stream was always weaker than the other engine.
the water pump was changed about 120 hours ago at the beginning of the season but the thermostat was changed 220 hours ago - start of last season.

Any ideas on cause?

Check again thermostat, and go further.when the engine is over heating just open top cover touch both the exhaust manifold and see which one is more hot and you can confirm it is really over heating.

Possibilities of overheating Impeller,thermostat ,but if you sure with those, it can be choked cooling passage with calcium deposit or probably corrosion on the end of water tube,

if you do regular flushing i dnt think it can block the cooling system withing 1400hrs ,but corrosion on the water tube is common for old engine,i have seen many case,

So if other things are perfect slip down the gear box and check water tube end you can see it with light, if you can see bulge rubber grommet,probably oil pan part is corroded,or if you cant see it connect water hose to engine water tube supply pressure water and see whether it is leaking from their.

hope this idea will help.


wajira

Agree with Wajira. But one other quick check is the possibility of clogged intake screens on the bottom of the leg. They are easy to remove, inspect and clean. I would also pull the t-stat covers and clean out any corrosion there and check the t-stats for correct operation. They should be fully open (3 mm) at 160 degrees F.

One other possibility is that a piece of the old impeller or a piece of corrosion broke off and is stuck somewhere in the water system. When you pull out the t-stats, put a garden hose in the openings, seal with a rag, and turn on the water for about 10 minutes. You might get lucky and blow out anything in there that is blocking the water passages. If you want to get fancy, mix a solution of Salt Away and pump it into the water system via the t-stat openings, let it sit for about 30 minutes (or whatever the instructions say) and then flush it all with fresh water as described above.

You were right.. it looks like it was the thermostat. I took the boat to my mechanic and watched as he replaced the thermostats... had a few surprises... 1st - on the bad engine, one thermostat looked perfect the other was very corroded. The inside passageways and hoses both looked pretty clear so he thinks that one of them wasn't changed last time they were supposed to be 1 1/2 years ago (which was with a different marina) and there was enough corrosion to cause some restriction in water flow.
Then he goes to replace the thermostats on the other engine, and found that one was missing. The other looked perfect.
I put about an hour and a half on the engines and no alarms, so I think it is fixed...
Has anyone ever seen a case where one thermostat is so much worse than the other?
Glad I stopped going to the old mechanic

I have noticed minor differences in the level of corrosion in the t-stats. But since I change them out about every 200 - 300 hours, it's never been an issue.

There is a strange quirk in my 225, and I assume in most others. I have external heat sensors connected to my manifolds. At idle, both read exactly 160 F, just as they should. But under power, the right manifold will drop to between 145 F to 150 F, while the left side stays at 160 F. Not one has been able to give me a logical explanation of why that happens.

I have noticed it too, at idle both read 71 c'-72 c' , once loading the engine one manifold temp drop to 61 c' other 68 c'. i identify the manifold with sensor numbers, number 1 is cylinder right bank(cyl 1,2,3) number 2 is cylinder left bank(cyl 4,5,6 with O2 sensor). chawk man can you confirm, is it same manifold did you mentioned left and right ?.

i thought about it, once engine is loaded temperature increase and thermostat will fully open then exhaust manifold get extra water from block, 1,2,3 cylinder position higher than cylinder 4,5,6 so more cool water reach to 4,5,6 cylinder side so that manifold cool bit more than other. any other idea ?

wajira

Wajira - that is exactly the same issue, but opposite sides, if I understand you post correctly. Cylinders 1, 2, and 3 are on the right side, and they are the ones that cool down at higher rpm's. Cylinders 4, 5, & 6 stay at 160 F (i.e. 71 - 72 C.) I'm sure it has something to do with how the cooling water travels through the block and manifolds, but it is not obvious from the water flow diagram I have in my Helm Shop manual.

Funny - I repowered recently with honda 225s. This is the first season for this engine- about 150 hours on the engine and this same problem popped up again. I did a search for it and found this old thread where it happened to me before.. so will be checking the thermostats tomorrow

Looks like it was the thermostat. The engine was new this year. How could something like this happen?

Hard to tell - installed incorrectly, fault in the manufacturing, not seated properly, who knows? At least you found the problem.