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Bf225a overheating at low RPM

T

Tomasga26

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Hello!!!!I have a 05 Honda BF225aAt low rpm about 1500-2200k for extended periods the overheated warning lights up.I just changed all plugs, oil, both thermostats, vertical shaft and bushing, and all related seals.Not sure what else could be causing this issue. Any advice? Motors have 450hrs +/-ThanksT
 
First of all, are you testing the engine on muffs? If so, you will get an overheat because the muffs on a garden hose cannot deliver enough water to cool the engine.

Make sure that you are really overheating. Get your hands on a heat gun, run the motor until the alarm goes off, and check the manifolds with the heat gun. If all is well, they should be about 160 F. If it is not really overheating, then one of your heat sensor may be going bad. There is a procedure for determining that, but let's first flush the engine.

Did you change the impeller yourself? If so, were there any fins missing. If so, that could clog up a water passage and cause the overheat. Drop the lower unit and check for any blockages around the water fittings. Then, with the lower unit off, remove each thermostat one at a time and seal in the end of a garden hose into the opening using a rag or duct tape and try backward flushing from each thermostat opening. Do this on concrete or use a large bucket so you can see if anything dislodged and came out.
 
Hello everyone sorry for the delay, been working too much. Finally got the new temp sensors in and also replaced the waning buzzer since I noticed it was defective.

took her out last night and the red light started to illuminate again. Check the pee hole and all looked good, very strong. Ran her for a while the buzzer dos not go off although I can hear the self test when I turn the key.

Used an IR temp and reading was 143F on both sides, compared it with my other outboard. Both read the same. Aside from this light she's running perfect.

now I'm really stumped! Maybe a ground issue on the block? Any ideas.

as walkways thanks for your help!!!!!!!
 
Let me make sure we all understand the situation and let us know if I am correct. When you first turn on the key switch, you see all four lights flash and the warning buzzer beeps twice, correct? When you start up the engine, the three red lights go out, and the green oil pressure light goes on, correct? You run the engine for awhile, and the red overheat light comes on, and the green oil pressure light is still on, but no warning buzzer, correct?
 
I see several possibilities. Hope others will chime in...

1. The wiring from one of your heat sensors to the ECU is faulty, breaking down when it heats up.
2. The pin from one of your heat sensors where it plugs into the ECU is corroded and is breaking down when the ECU heats up.
3. The pin out of the ECU to the wiring harness, to the warning light is corroded or loose and is breaking contact when the ECU warms up. Unfortunately, I do not have my shop manual with me to tell you which pin it may be. If you can get your hands on a Helm shop manual you can look at the wiring diagrams in the back and figure it out.
4. You have a bad connection where the wiring harness plugs into the key switch console.
5. You have a faulty ECU. The only way to test that is to swap it out with a known good ECU.

Items 1-4 above should be explored before going to item 5. I would start by shunting the service connector and pulling any fault codes. If it is wiring between the sensor and the ECU, you should get a fault code 24 for heat sensor 1, or a code 25 for heat sensor 2. If you get no codes, concentrate on the wiring and connections from the ECU to the key switch. If you have access to the Helm shop manual, go to page 5-56 for the detailed test procedure.

If you need the procedure for pulling fault codes off the ECU send me an e-mail at [email protected].
 
OK. If no codes then the problem is likely somewhere in the wiring harness or more likely in the key switch panel itself. I'm not sure how the light is activated, but I suspect that normally the ECU sends a low voltage signal up through the wiring harness to the light. Find and mark the connector to the overheat light from the wiring harness. (Sorry I don't have my shop manual with me to tell you the color of the wire.) Anyway, run the boat until the light comes on, then unplug the connector and measure for any voltage coming through the harness. That should isolate whether the problem is in the harness of the key switch.
 
I had a Yamaha 225 Four stroke that did this and it is common. The problem is the cooling pressure relief valve is corroded and stuck open allowing the cooling water to bypass. During high RPMs the pump can overcome the loss of cooling water thru the relief, but at idle or low RPMs the pump volume is less and starving the motor from cooling water. On the Yamaha you can pull the relief valve and clean it or replace. It should be obvious when you pull it and see salt crystals and deposits.
 
Looking at the picture in the manual, it is under a cap that has two bolts and a small tube attached. it says to remove tube and two bolts, remove relief valve cover. looks like a five minute job. A lot easier than the Yamaha.
 
It is item 15 and associated parts on diagram attached
 

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Well I'm happy to report that after two long outings I have not seen the light anymore. I unplugged the harness on both temp sensors and sprays with silicone. While that seems to have worked I'm unsure how as I did not see anytype of corrosion on the plug(harness) but figured I'd try it anyways so there must have been some.

thank you all for your help on this; it is greatly appreciated
 
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