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Honda BF75 Cuting Out

Maynard530

New member
Hello all. My Honda BF75 runs great for about 10-15 minutes. When I have it all the way open, it dies on me. Starts up with one pull immediately after, runs about a minute, then dies. I took the cover off, noticed water dripping from the hose coming out of the thermostat manifold. Could that be the problem?
 
Do you think it may be overheating?

There is a "bypass tube" (#8 in service manual cooling system diagram). If t is leaking, it WILL cause overheating.

If overheat is occurring and the engine is shutting itself down as a result, you could be damaging your engine by continuing to run it.

Repair that leak before running it anymore.

Give us some background on how this came about. Did it run great for a long time and just started doing this?

Or, is this a recent purchase? Those sorts of things.

If you get the water leak repaired and it still wants to quit running, try it with the engine cover off and see if that makes a difference.

But, whatever you do, keep a close eye on the temperature. Buy a cheap, infrared, non contact, thermo gun from Harbor Freight Tools . Well worth the money to protect your motor.

This engine should run at no more than 165 to 175 degrees Fahrenheit.

Let's see if we can get her straightened out.
 
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Do you think it may be overheating?

There is a "bypass tube" (#8 in service manual cooling system diagram). If t is leaking, it WILL cause overheating.

If overheat is occurring and the engine is shutting itself down as a result, you could be damaging your engine by continuing to run it.

Repair that leak before running it anymore.

Give us some background on how this came about. Did it run great for a long time and just started doing this?

Or, is this a recent purchase? Those sorts of things.

If you get the water leak repaired and it still wants to quit running, try it with the engine cover off and see if that makes a difference.

But, whatever you do, keep a close eye on the temperature. Buy a cheap, infrared, non contact, thermo gun from Harbor Freight Tools . Well worth the money to protect your motor.

This engine should run at no more than 165 to 175 degrees Fahrenheit.

Let's see if we can get her straightened out.

I bought it used spring of 2016, it ran great all summer. Over the winter I put a new thermostat and manifold gasket in. On the parts diagram that hose I said was split is listed as a "bypass hose," so that might be my problem. I cut the 1/8" split off the end, put the clamp back on, along with 2 small zip ties. No leak anymore. Ive only run it in a barrel since the problem started, so hopefully next time on the water it will run like a champ!
 
That hose is listed in the parts diagram as a "Bypass Hose" so that might very well be the problem! I snipped off the 1/4" split at the end of the tube, put the clamp back on, along with 2 small zip ties. No more leak. Its only ran in a barrel since the problem occurred, but hopefully it runs like a champ again when I get it back in the water!
 
Ok, keep a close eye on the head temperature. Overheating is the quickest way to turn one of these into a lightweight mooring or a barn decoration that I can think of!

Good luck.
 
Ok, keep a close eye on the head temperature. Overheating is the quickest way to turn one of these into a lightweight mooring or a barn decoration that I can think of!

Good luck.

Will do! Thank you so much! If I was to buy a thermo gun, do I point it at the bypass hose?
 
Well, you would want to point it EVERYWHERE! After all, you have to have fun with your new toy!
But, what you're going to be most interested in is the cylinder head and block temp.

The temp gun shoots a lazer marker and reads the temp that bounces back from that small surface area. Pick several places that are clear and fairly flat for the beam to strike and signal to bounce back from. The temp should be consistent across the surface of the cylinder head and should not exceed about 180 degrees.

There are two thermostat ranges that were available for these engines.
One was 140 to 150 degrees and the other was 158 to 176 degrees f.

If the engine doesn't get up to at least 140 degrees that would indicate a thermostat that is stuck open and it should be replaced.

Good luck.
 
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