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Noise Alarm when under power 2002 50 hp

C

captb

Contributing Member
"i've been lurking a while, but this is my first post.
the question i have is for a 2002 bf 50 tiller model.
i recently changed the impellar out because it was not pumping a very strong stream. the new impellar has fixed that, but the trip before i replaced the impellar i noticed a noise, it could be an alarm, don't know what it's supposed to sound like. motor never slowed up, no attempt at a "safe" mode that i could tell.
either way, if it's an alarm, i can't figure what it would be for. good water, no warning lights, nothing else wrong that i know of.

maybe thermostat? anyone have any ideas.

thanks, brandon"
 
"I know this is tough to do in

"I know this is tough to do in print, but can you describe the noise? It might help others here help you.

Also, include throttle setting, ie: idle, high cruise, low cruise, all three. And, do you hear it in gear-nuetral-both or forward-reverse-both?


Do you know what it sounds like up against the rev limiter and is it anywhere close to that noise?

Also, did the noise go away after the impeller was changed? It's not clear in your post if you still hear the noise."
 
"well the noise is almost like

"well the noise is almost like something is vibrating under the cowl, but it's too consistant to be just that i think. it's almost like a buzz. i don't know what the alarm sounds like, but this is an interrmittent buzz (sort of). i don't know what it sounds like at the rev limiter. i have a feeling this isn't it, since it does it from anywhere above an idle on through.

idling, no noise, as it picks up rpm's i notice it more. not that it gets louder or faster really, just that it doesn't go away.

no, apparently, the impellar did not make the noise go away. and i don't know if the noise started because of the impellar or not.

just don't know alot about this motor. i've had 2 stroke yamaha's for years. this is my first foray into the 4 stroke world (on my duck skiff. it appears to be a good, (super) strong motor.

just can't figure this out"
 
anybody out there?

could it

anybody out there?

could it be the thermostat not functioning properly so it could cause some sort of alarm?
 
"I don't work with anythin

"I don't work with anything but the 20 horse on down so I can't tell you if there is an audible alarm on your tiller 50. The 20's I work with are silent but they are electric start with remote control and the alarm is in the remote. Overheat on the tillers cause a power down and low oil pressure causes power down and green light not to function. Have you checked all the screws in the side covers for being loose/missing? These motors do create a good deal of harmonic vibration and will cause just about anything to shake that isn't held solid. As an example, I've needed to change out several throttle and shift cable quick release clips due to vibration deterioration.

Another thing that comes to mind is; have you changed the way you've loaded the boat lately, possibly bringing the motor up in the water some? Because exhaust noises can be less muffled if the motor is raised, you might notice them more.

Have you run the motor on the rabbit ears and listened for the noise? With the cover off, you could watch for movement associated with the sound. Just watch out for that flywheel spinning and don't have any fingers, neckties, long hair or kids nearby when you do it. Keep looking, you'll find it."
 
"Right on Jimmy!

Brandon, u

"Right on Jimmy!

Brandon, use a short hose to your ear to help locate the origin of the noise.

Some of the 50's had a key switch to start, others just a buttom. If you have the key switch, the alarm is with the key switch assy. If you have the button start, the alarm is located under the hood in the center front of the motor.

If you run it on rabbit ears, be sure to tape up the intake that is located on underside of the cavitation plate just above the prop. Otherwise, you may be changing your impeller again.

Do you hear the noise in and out of gear?

A couple of thoughts...

1. If it is heard only in gear, if you have a spare prop...change the prop. I have seen some cases if the prop hits something, it can cause a slight vibration that is amplified through the engine and it sounds like there is something wrong with the motor. This seems to occur mostly on 40's and 50's.

2..If you can hear it when it is not in gear...listen for the sound from under the flywheel. Does it increase pitch (not only loudness)as you increase rpm? It could be coils under the flywheel coming loose or the magnets on the flywheel delaminating and hitting the coils.

3..Although you said it started before you changed the impeller...it could be possible that you did not connect the shift shaft up correctly when you put the lower unit back on and the clutch dog in the lower unit could be ratcheting.

Between that and what Jimmy said...should keep you busy for a while.

Good luck!!!"
 
Thank you Mike for keeping me

Thank you Mike for keeping me from helping the guy ruin his waterpump! I always use a test tank and never the "ears" so I was ignorant of those intake holes being a problem. Still a rookie in oh-so-many ways!
 
"Thanks guys, i've just ab

"Thanks guys, i've just about figured out i need a new thermostat.

i'll let you know if that's the fix in the next couple of days just as an fyi.

thanks again for the insight."
 
"oh yeah, forgot to ask, as me

"oh yeah, forgot to ask, as mentioned above. is the impeller in these things really that sensitive. i've run yamahas and evinrudes for years and the impeller in those have never been that "touchy" to running without "full flow". i did not know that i should tape up that other pickup, but will from now on, although, i usually just back it overboard.

i have a feeling i'll be replacing the impeller again anyway in the spring after all this cold weather we've had for the last two weeks.

thanks again!"
 
"So I guess it turned out to t

"So I guess it turned out to the the alarm that was going off.
If you find a lot of debris accumulated around the thermostat, it might be good to take your lower unit back off and backflush from the thermstat back through the pickup tube.

Most Yamahas and Evinrudes do not have the extra water pickup so you do not have to worry about it. Each motor is different."
 
"still don't know about th

"still don't know about the alarm thing, but after talking with several mechanics in the area (none of which are CERTIFIED honda mechs.) the conclusion is to replace the thermostat.

the noise is only under power, in gear, above a high idle. can't find the noise if it's just revved up.

either way, i meant is the impeller that fragile, itself. the ones i've had on other motors are just TOUGHER than that. just curious.

thanks, b"
 
"If you are not sure if it is

"If you are not sure if it is the alarm going off, I can not understand how a bad thermostat will make a noise.

I hope that fixes it.

The Honda impeller is not any more fragile than the other brands. Any of them will burn up if you do not have enough water. If the extra intake is not covered up, the impeller will be sucking air. That is not good for any impeller.

Good luck!"
 
"Mate do what they say and hav

"Mate do what they say and have a look under the fly wheel. From my limited experience it is easiest to use a rattle gun to get the four bolts out (after you have removed the plastic covery thingo)

Mine had this whine I thought was an alarm. It was a magnet that had delaminated and was stuck between two other magnets sitting just forward of its usuall position. Under load it made this high pitch whine like some mad alarm system. It was impossible to find until I took it all apart. I was lucky i did look, it was slowly wearing out the covers on my coils!! Nice

I live in the NT of Australia, it is very isolated and everything is a long run in the boat. I use my boat lots. I didnt change my impeller for 3 years. I changed it cause it got full of sand, but although it was a bit stuck in one shape, it was still pretty whole. I think they are pretty good really..

The blokes above give good advice from my experience. Dont get stuck one one course of action, use their knowledge where you can I say"
 
thanks for all the insight eve

thanks for all the insight everyone. the reason i came to the thermostat conclusion is because the noise has to be an alarm. last night i found that to be true after testing the alarm.

probably a combination of a thermostat that needed replacing and an impeller that i guess is somewhat fragile.

i'm crossing my fingers that the alarm is not faulty.

thanks again.
 
"[i]If you run it on rabbit ea

"If you run it on rabbit ears, be sure to tape up the intake that is located on underside of the cavitation plate just above the prop. Otherwise, you may be changing your impeller again.

Mike, curious here .... i've been flushing my bf50 for 5 years with muffs and only just recently heard about taping off the pickup under the cavitation plate.
no harm so far ?? impellor recently changed
and no signs of wear.
Am i missing something ??"
 
"yeah, from what i can tell sc

"yeah, from what i can tell scott has been lucky. new thermostat on the way, another impeller replaced, should be fixed once the thermostats in.

anyone know what the operating temperature for these motors are?"
 
"You should check the marking

"You should check the marking on your thermostat but the thermostat should generally start opening around 126 deg F and should be fully open around 144 deg F. If the engine temperature is around 135 -140 F, that should be good."
 
"so, i think i've got this

"so, i think i've got this thing whipped, finally!

quick question though, after running it at the ramp yesterday afternoon: should the water from the tell tell be warm? it wasn't hot and never got too warm, but i just don't remember my yamahas or evinrudes ever being anything but cool.

i ran the motor for a good 30 minutes and checked the temp by had after about 15. that's when i discovered the warmth, but i never got any warmer. i ran it through a wide range of rpm's, so i think it's alright, but maybe someone could tell me if i should be concerned.

thanks!"
 
Once the engine warms up the t

Once the engine warms up the telltail will be a little warm depending on the ambient water temperature.

If you are getting no alarm...that is good!
 
"alright, ran it about an hour

"alright, ran it about an hour and half this afternoon and by the end of the run it's just dripping water out of the tell tell.

what's the next move?

alarm did not go off today, though."
 
"It could be a couple of thing

"It could be a couple of things.

Most likely it is just some debris clogged in the outlet of the telltail. The hole there is very small. If it is stopped up, it will not affect the cooling of the engine.

Pull the little hose off the other side of the outlet and stick a paperclip through the hole of the outlet. You will probably see the debris. It may also help to blow back through the little hose that goes into the block,if you have some compressed air. You could also just blow in it with your mouth.

If you just see small pieces of debris, you are probably ok.

I hope you backflushed from the thermostat to the pickup tube (as mentioned in 1/7/10 post) If you did not find all the pieces of the any of the impellers that you changed, you may have a couple of the impeller pieces blocking the passage to the tell tail. Blowing back through it may temporarily fix it or it might even blow back far enough into the system for it to flush through on its own (although not very likely)"
 
"Most likely you have some deb

"Most likely you have some debris that worked it's way into the tell tale circuit. Maybe a small chunk of the old impeller? I find small twigs, shells and various other assorted junk in the ones I work on.

I do NOT like trying to poke anything into the tube to clean it out though. The twigs have taught me to take the tube off and look into the pipe and fish them out. If you poke at stuff in the tube, it usually just comes back and re-clogs the tell tale later. Hope that's all it is anyway."
 
"yeah, i did flush it between

"yeah, i did flush it between impeller changes. i'll keep messing with it and hopefully fix it. it's just frustrating during duck season!

something i just thought of, what if i let it pump water with the fitting removed from the side of the block, just to let it flush that way?

i also, got rid of the nipple at the end of the water hose that connects to the motor cowl. i "straight piped" it with a longer piece of hose and just ran it out the old hole to get rid of that constriction at the nipple. i had done that with all my motors in the past so i did it to this one too.

thanks for all the help and input from everyone!"
 
"I would not just let the wate

"I would not just let the water come out of the block without a hose.

Letting the hose stick out through where the telltail nipple was can work. You may also want to get a slightly bigger hose (even a clean plastic hose to replace the existing hose to minimize debris blockage.

Depending on where you are hunting, you could be picking up some sand and muck and it could be getting plugged at the nipple on the block. Once again, you may be able to clear it with air or a wire into the block. I see this on a lot of work boats with 40hp's that work in shallow water.

If you do not get the water out from under the hood, it could be sucked into the intake and damage your engine.

It sounds like you almost have it licked."
 
i'm just going to drop the

i'm just going to drop the lower unit and take the thermostat back out this weekend and use the compressor to blow back through everything. i have a feeling there's some debris like you described in there somewhere.

i don't run it shallow. where we hunt its just used to get from blind to blind or haul people. rarely use the trim because we're never that shallow.

i did put a little bigger hose on the nipple from the block and fed it out the old hole once i removed the nipple on the outside of the cowl. those things ice up quick and i've always been amazed how long it takes for them to unthaw.

thanks again and i'll let y'all know how this pans out.
 
"alright, no alarm today and g

"alright, no alarm today and good pressure on tell tell.

any chance that a heavier load would cause the engine to heat up more? it makes sense in my mind, but just like to hear what y'all think.

today, had one less person and 4 dozen less decoys and no trouble and decent "pee" stream."
 
"well, i did some deeper diggi

"well, i did some deeper digging and found pieces of gasket stuck behind the nipple on the block that goes to the tell tell.

maybe that info will help someone else out in the future.

good pressure today running it 4 hours total.

thanks for everyone's responses and ideas!"
 
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