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2012 BF40D overheat problem

Z

zsam1

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My boat has a 2012 Honda BF40DK2 - LRTA. A test run was conducted with the seller for about 20 minutes from idle to 30+ mph. No problems. Trailered home and got out on a local lake and within 15 min the motor began stalling and eventually quit. It would not start again and the temperature lamp was on. I since replace the thermostat and water pump system in the lower unit from the base to impeller to housing. took the boat to the ramp, sat on the ramp with the motor in the water and ran the motor for 10+ minutes at different rpms and some in gear but mostly in neutral. Stream out the back was good at idle and increased with higher rpms. thought ok i'm good to go. moved out the water, unhooked the tie downs, backed back down the ramp, started the motor and pulled over to the courtesy dock. Motor off, tie to the dock. Parked the car and trailer and back to the dock. untied the boat and started floating away from the dock and the engine would not start. when the key was turned the green oil lamp comes on and the red heat lamp comes on and the alarm buzzes 2 times. then both lamps go off.

1) will using the flushing port above the lower unit push out any possible blockage? and where does the water come out when using the flushing "WASH" port? I assume the pee whole.
2) what exactly is the flow of water in the BF40 anyway? Anyone have a diagram? > intake ports > pump > vertical tube to where
2A) where in the sequence is the thermostat and water jacket?
3) When I pulled the old thermostat it did not look too bad. not much corrosion if any to speak of.
4) Should I pull the water jacket and look?

I'm at a loss at what the next steps should be.. Thanks for suggestions.
 
With a complete new pump, including housing in place, my first move would be to remove the lower unit, pull the water pump, and search below it to look for pieces of old impeller. While apart, if you wanted to back flush, you could do that easily with the lower unit removed. Just remove the thermostat (t-stat) cover and t-stat and pour some water in it. That should have water coming from the pipe that would normally carry to the motor from the pump. At this point, with everything apart, you might want to verify that it has the right t-stat in it. There are 2 that will fit fine, with the one for earlier (carbed) motors opening at a higher temp (80c/180d) than the newer one used for injected motors(60c/140d). As they appear identical without very close inspection, that's an easy mistake to make. Been there.... If all checks out fine, you're going to need to find out if the motor really is getting hot, or does the ECU just think it's hot? Easiest way is with an inexpensive infra red thermometer (20 bucks). Does this motor have a salt water usage history? Best of luck -Al

BTW- note that running these 40 and 50 Honda's on muffs is a bad plan due to the extra water intake right above the prop. You need to have really good flow and pressure available to just run it at an idle! Anything over an idle will very likely smoke that new pump. Water barrel or cut down trash can full of water is a MUCH better plan. If going that route, realize that the water level MUST come up above where the impeller resides.
 
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Those are good suggestions Al and I'll work through them and get back to you. Should I replace the 2 seals between the gears and the water pump? I have had the water base off and replaced already. Thanks.
 
Just over the screen under the cab plate with a bit of duct tape and flush normally. I would clean out the exhaust side water jacket , clean out and replace internal anode at the same time. This is a common area of blockage on saltwater motors
 
zsam1 said:
Those are good suggestions Al and I'll work through them and get back to you. Should I replace the 2 seals between the gears and the water pump? I have had the water base off and replaced already. Thanks.
Click to expand...
Regarding the seals, as we're working on a '12 motor, I have mixed emotions. Likely though, as inexpensive as they are, I'd probably replace them. Regarding water pump removal, I get you have new/good parts. We're removing it again so we can do a good inspection, looking for crap (like old water pump vanes) in the passage UNDER the pump, and above the intake grills on either side of the lower unit. -Al
 
In speaking with the original owner, I don't believe the boat has been in saltwater. I did find some sand in the thermostat area when I replaced the T. I have a water jacket gasket so I'll include that task as well.
 
Hi everyone,
So an update. The problem may not be overheat. A small leak was detected in the biscuit using an air pump. The biscuit, rubber seal between the lower unit gear oil and the impeller housing has been replaced. Along with a new impeller and gaskets. This corrected the lower unit leak. Tested good stream.
Being a newby I mis understood the two beeps that occur when the key is turned. So it was not an overheat problem. when running the green oil light is on but no other lights or alarms occur.
The symptoms are - the motor running at idle for 15-20 minutes then limping, then it dies and will not restart. so we changed the high pressure filter. The old one was brown and looked a bit clogged. We also thought the fuel tank cap was not venting properly, so put on a different fuel tank cap. Surprising after we then let it set for an hour we then backed it down the steep boat ramp and ran the motor in the water while still on the trailer. It ran for 30 min and did not die at various rpms, in gear, out of gear, idle... so I took it to another ramp some 3 hours later and put in the water. Started up, launched and idled over to the courtesy dock and left it idling. Parked the trailer and came back, still running. Then left the dock and not 50 yards later the engine started coughing a bit. I tried to go faster but it bogged down. it died the second time i tried to throttle up. it did restart one time and so Iheaded back to the dock. it would not accept any more throttle and only idle. before it got to the dock it died.
All this to say I'm wondering if, as I have read in previous posts, it might be the grommet in the VST tank? Does anyone think this could cause this problem? Is removing and replacing the part too difficult for a DIY mechanic? Thanks!
 
Regarding that grommet, the tendency is to install it incorrectly. The tendency (for whatever reason, including myself until learning better), is to slide it into the hole, then install the pump. That will almost guaranty the grommet will bunch up as the pump is pushed into it, causing tons of difficult to diagnose issues. Instead of pushing it into the hole, slide the grommet onto the pump outlet, then reinstall the pump. EZPZ. No more issue. -Al
 
Anyone have a video, pictures, or link to one of these showing the removal, repair, and installation of the VST in a honda BF40D or BF50D ?
 
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