Logo
FULL SITE MENU

BF20 overheating

T

Tedmarx38

Member
Starts fine, overheats in ten minutes. Suppose I’ve verified that the thermostat’s fine, the impeller is too and no chunks or debris from it in the system. What else remains as a possible cause?
 
Hi,

Not much info provided.

Is this actually a post 2002 BF20D or an old pre 1997 BF20?

How long have you owned it? Bought new? Used?

Did this just suddenly start happening?

What does "thermostat's fine".mean? You tested that it opens fully in 140°f to 150°f water?

Did you replace impeller or just look at it? How did the other pump parts...ie: housing, liner (cup) and cover (wiper plate) look?

Many,.many problems like this stem from poor pump efficiency because those parts are worn or damaged but "look ok" to alot of people if not closely inspected. They have fooled me before when I didn't look carefully

Sometimes using a complete kit instead of just an impeller can cure the problem.

Other possibilities...

Debris like paper or moss in water intakes.

Mis-aligned water tube

Torn/damaged/missing water tube grommet or water tube seal ring.

Good luck.
 
Fresh water. It is post 2002. The impeller was brand new last spring and only used once - overheated. Sat all summer and the test run in water yielded the siren. I took it apart and reinstalled the impeller as I’ve had these in wrong prior. I can’t tell it is was in wrong because when I took the assembly apart yesterday it fell out before I could inspect it. Looks fine and I reinstalled it and repeated the test, after first flushing through the hose adapter. This time it ran 14 mins under idle and higher rpm’s for 14 minutes. The telltale stayed steady and never exceeded 80 degrees or so and the engine block never got above 120. The next test is running it with prop removed under the load of turning the gears, and then onto the water we go.

i mentioned thermostat as “assume it’s fine” as I wanted to avoid respondents focusing on that. Should it fail again I will take it out and fully flush with system with hose water and Compressed air.

It’s done this many times over the years and the thermostat has never been a problem. There’s no leaves or filth in the screens or system but I flushed it in case an old impeller part was maybe left over from before (I doubt it though as I’ve never removed one that was missing a chunk).

My guess is if it still fails that it’s some sort of blockage. I’m curious though about other rare causes, hence the way I worded it.

Thanks as always for insights.
 
Fresh water. It is post 2002, bought used from the original owner who kept it in excellent condition. Motor runs fine. Everything does except the overheating. I think it’s a 2007.

The impeller was brand new last spring and only used once - overheated. Sat all summer this year and the test run in water yielded the siren. I took it apart and reinstalled the impeller as I’ve had these in wrong prior. I can’t tell it is was in wrong because when I took the assembly apart yesterday it fell out before I could inspect it. Looks fine and I reinstalled it and repeated the test, after first flushing through the hose adapter. This time it ran 14 mins most under under idle but also at higher rpm’s.

The telltale stayed steady and never exceeded 80 degrees or so and the engine block never got above 120. The next test is running it with prop removed under the load of turning the gears, and then onto the water we go.

i mentioned thermostat as “assume it’s fine” as I wanted to avoid respondents focusing on that. Should it fail again I will take it out to test (it’s never failed the test) and fully flush with system with hose water and Compressed air.

It’s done this many times over the years and the thermostat has never been a problem when tested in hot water after removal. There’s no leaves or filth in the screens or system but I flushed it in case an old impeller part was maybe left over from before (I doubt it though as I’ve never removed one that was missing a chunk).

My guess is if it still fails that it’s some sort of blockage. I’m curious though about other rare causes, hence the way I worded it.

Thanks as always for insights
 
If the telltale is strong not likely a blockage. Have you checked the actual sensor. I’m pretty sure if you take out the sensor and check the resistance while cold it should show an open circuit and when hot the resistance should be low. You can just replace it for under $50. When out on the water and the alarm sounds does it go into limp mode?
 
No limp mode as I don’t recall it ever being left running for more than a few seconds once the buzzer rings.

By sensor do you mean thermostat? Thanks as always.
 
The sensor is what makes the alarm go off. It detects that your engine is getting too hot and then the alarm sounds. This has nothing to do with the thermostat. Find where the overheating sensor is on your engine and see if it’s operating correctly. You should be able to test it or just replace it.Things don’t last forever especially $50 parts. The reason I suspect the sensor is you said the water coming from the telltale was 80. So the engine block seems cool so why would the sensor close to produce the alarm. Maybe it’s reached its eol and needs replacing. An idea anyway.
 
weathered said:
The sensor is what makes the alarm go off. It detects that your engine is getting too hot and then the alarm sounds. This has nothing to do with the thermostat. Find where the overheating sensor is on your engine and see if it’s operating correctly. You should be able to test it or just replace it.Things don’t last forever especially $50 parts. The reason I suspect the sensor is you said the water coming from the telltale was 80. So the engine block seems cool so why would the sensor close to produce the alarm. Maybe it’s reached its eol and needs replacing. An idea anyway.
Click to expand...
Thanks. To clarify it was the time before when it squealed. The test run you’ve referenced was after I removed and reinstalled the impeller. I’m hopeful it’s all working properly since nothing overheated but the real test will be with the gears engaged and then on the water.
 
Back
Top