bf15 HELP HELP!

[coronadojeff]

i went out to do a trial run with my new to me 15hp 4 stroke honda. ran fine for an hour or so, then when i had it up to half throttle for maybe 5min, it made a weird noise, i throttled down and thought that maybe the belt was slipping. i shut it down and it locked up. i removed the plugs and its still locked up. there was a good stream of water coming from the cooling system so i know it wasn't over heating. still has plenty of oil. it just wont turn. where do i start to look for problems? i have a repair manual and am a pretty good wrench, just don't know where to start. thanks

 

[Mas]

Re: bf15 HELP HELP!

Get some penetrating oil down into the cylinders and let it soak. Any chance the wrong oil was used?

I would also check/replace the thermostat. Did you feel the motor? Just because you had a good stream from the tell-tale, it doesn't guarantee it won't overheat.

MAS

 

[Mas]

Re: bf15 HELP HELP!

And also, check to make sure you have the correct spark plugs that are gapped correctly.


MAS

 

[coronadojeff]

Re: bf15 HELP HELP!

i pulled the head off the motor and it looks ok. the pistons are seized to the cylinders but i have them soaking. when i pulled the thermostat housing theres nothing in it. is there supposed to be a thermostat on this motor? i originally was thinking its an oil problem but now im thinking overheating. and does any one know if theres a port to hook up an oil pressure gauge?

 

[kissmywake]

Re: bf15 HELP HELP!

Take out the oil pressure sensor and screw in your gauge there. Was the green light on? What model is the engine? BF15A or BF15D?

 

[coronadojeff]

Re: bf15 HELP HELP!

i think its a bf15a. im not too sure if the light was on or not. im thinking it wasn't. while waiting for responses i went ahead and pulled the powerhead off the motor and pulled it down. i didnt remove the pistons from the cylinders. they are freed up thoe
, and the motor looks pretty good. one of the rods has some gouges out of it where it rests on the crank, but the crank side looks pretty good. its the cylinder closest to the oil pan. i scraped some carbon off the pistons and checked it all out for burnt oil or any sort of discoloring. i think i might have saved it by shutting it down right away. it has to be either a coolant or oil problem but right now i cant tell. i guess i'll weight for some one to chime in or got to the dealer and talk to a mechanic tomorrow.

 

[kissmywake]

Re: bf15 HELP HELP!

Judging by the the fact that the green light may have not been illuminated and the damage to the cylinders and crank, I am thinking lubrication was the cause. When you drained the oil, what did it look like? If it was black and thin, and there truly was no thermostat like there should be, that certainly would have caused the oil to become contaminated with fuel and cause it to be less effective as a lubricant. The easiest way to tell BF15A from a BF15D is the hood. The A will have a squared off hood and the D will have a rounded hood.

 

[coronadojeff]

Re: bf15 HELP HELP!

how would no thermostat cause fuel in the oil? and yea the oil was pretty black and thin. but there wasn't any metal in it. should i rebuild the oil pump? i cleaned out the oil pick up screen and checked the passages, no blockage so im guessing the oil pump was the culprit and the lack of thermostat.

 

[kissmywake]

Re: bf15 HELP HELP!

how would no thermostat cause fuel in the oil?

When a 4-stroke water cooled outboard has no thermostat, there is no heat, actually it pretty much takes on the temp of the surrounding water which can get quite cold. When you don't get an engine warm, the piston rings never expand. When they don't expand, they don't seal. Then when an engine is cold, the fuel doesn't atomize well. When this happens you end up with an excess of fuel running past the piston rings and into the crankcase which contaminates the oil.

 

[coronadojeff]

Re: bf15 HELP HELP!

so i took the motor in to the mechanic and he couldn't tell me indefinably what had happened, so i went ahead and ordered a new rod, oil pump, impeller, thermostat, gaskets, & piston rings, figured while i have it pulled down i might as well replace them. also got some honda oil. should have all the parts by friday and then on to the rebuild, hope fully testing it the sunday after, maybe.