Motor-tone changes at wot

[Big Jay]

Talking about my '58 Johnson FD-12 again, maybe this is normal, I don't know....

The only way I can describe it is if you voiced a flat vowel "Aaaa" and held it, this would represent the normal "tone" of the motor at WOT. Now, if while holding the "Aaaa" you changed it to an "Oooo" and voiced it audibly louder, that is what's happening. It will continue to hold the "Oooo" until I slow right down, then goes back to normal. It almost sounds like the exhuast is lifting out of the water and is no longer muffled by being submerged...

Also, it doesn't happen all the time... no pattern, just once in a while, enough to scare the hell out of you :watermelon:. The performance doesn't seem to affected, nor the rpm's.

If you tell me this is normal, I'll go with it I guess.... just seems wrong.


Thank you again for sharing your experience with me

 

[Big Jay]

Re: Motor-tone changes at wot

Has anyone ever had this happen?

 

[RSchendel]

Re: Motor-tone changes at wot

I had a similar experience with my '58 Evinrude 18 a couple of weeks ago. The problem was the impeller slowly failing. It was noisier as it got hotter at WOT. The brass hub on the impeller spun as the bond failed.

 

[Big Jay]

Re: Motor-tone changes at wot

I thought the impeller was held in place by a pin in the drive shaft, what "bond" are you referring too?

I feel like I should know this lol

 

[kenadian]

Re: Motor-tone changes at wot

I have the same thing happen on a 1959 Evinrude 10 HP. I've been running it for 3 years now like this and have had no problems.When the motor sound changed( like you described). I checked impellar water floe,temperature etc. and found nothing out of the ordinary. I decided to run it til it blows up (then I'd know what it was) but the thing just keeps running great different sounds and all.

 

[Big Jay]

Re: Motor-tone changes at wot

I have the same thing happen on a 1959 Evinrude 10 HP. I've been running it for 3 years now like this and have had no problems.When the motor sound changed( like you described). I checked impellar water floe,temperature etc. and found nothing out of the ordinary. I decided to run it til it blows up (then I'd know what it was) but the thing just keeps running great different sounds and all.

Ya... I'd rather not let it get to the point of blowing it up , I plan on running this thing for years to come.

Thanks for the reply just the same tho

 

[kfa4303]

Re: Motor-tone changes at wot

Hi Big Jay. Is the motor in the locked position while underway? If not, the leg may in fact be lifting out of the water slightly as you gain speed. Make sure that the motor is set to the right height on the transom too. You want the anti-vent plate, found just above the prop, to be level, or slightly higher than the keel. However, as long as the motor is pumping plenty of water and responds normally to throttle, you should be fine. Do a search on youtube for vids of motors similar to your own running WOT for comparison.

 

[Big Jay]

Re: Motor-tone changes at wot

Hi again KFA, thank you for the reply.

Forgive me if I'm wrong, but is the leg of the motor not more prone to lift out of the water while in reverse as opposed to forward gear? I figured the forward thrust would keep the leg tight against the transom... Either way, it's done it in both the locked and released position. I keep it unlocked once I'm trolling in case I hit an obstruction in the water, but it's always locked to pull away from the dock in reverse and usually stays that way till I get to my desired zone on the lake.

 

[RSchendel]

Re: Motor-tone changes at wot

The impeller slippage I found was not between the driveshaft and the brass hub of the impeller, but the brass inner hub and the rubber portion. The pin was just fine. The impeller visually looked fine until I noticed that I could spin the inner hub with no rubber part movement.

 

[Big Jay]

Re: Motor-tone changes at wot

Ah ok!!

I get it now, I will disassemble, check and post my findings... Thanks RSchendel

 

[aerobat]

Re: Motor-tone changes at wot

The only way I can describe it is if you voiced a flat vowel "Aaaa" and held it, this would represent the normal "tone" of the motor at WOT. Now, if while holding the "Aaaa" you changed it to an "Oooo" and voiced it audibly louder, that is what's happening. It will continue to hold the "Oooo" until I slow right down, then goes back to normal.

the engine is trying to tell you something and you should hear to it .

at part load its telling you "aaaa"-r you kidding me ? give me more !!!
when you then give WOT the engine tells you "oooo"- yer baby , thats how i like it !

:laugh:

 

[1NewBoatGuy]

Re: Motor-tone changes at wot

the engine is trying to tell you something and you should hear to it .

at part load its telling you "aaaa"-r you kidding me ? give me more !!!
when you then give WOT the engine tells you "oooo"- yer baby , thats how i like it !

:laugh:

THat's what I was thinking too... Keep given her, she enjoys it. Old ladies make the same noises when you give it all you got

 

[Big Jay]

Re: Motor-tone changes at wot

I agree she's telling me something lol....:lol:

But this happening "while" at WOT... not on the way up

 

[bbstacker1]

Re: Motor-tone changes at wot

Big Jay, I know the exact sound you are talking about. I have a 61 FD-15 that I run on a 21 ft Scott Hudson Bay canoe that does the same thing. I have noticed if I gradually slow down after it starts doing it, the sound will change back at a certain point, I think it has something to do with water flow in or around the lower exhaust port. At any case it doesn't seem to affect the operation of the motor (speaking for my engine only).

 

[Big Jay]

Re: Motor-tone changes at wot

Big Jay, I know the exact sound you are talking about. I have a 61 FD-15 that I run on a 21 ft Scott Hudson Bay canoe that does the same thing. I have noticed if I gradually slow down after it starts doing it, the sound will change back at a certain point, I think it has something to do with water flow in or around the lower exhaust port. At any case it doesn't seem to affect the operation of the motor (speaking for my engine only).

This sounds exactly like my problem bbstacker1, if I slow it goes back to normal too and I sometimes don't need to slow much. I had originally suspected a flow issue in the exhaust port too, but thought maybe that was too simple... maybe wrongly so. It's almost like the port on the foot is coming out of the water just enough to no longer muffle the engine, and slowing down it covers it up again...


This is my relationship between my transom and cavitation plate, a little off but enough to cause this issue I wonder?

 

[Watermann]

Re: Motor-tone changes at wot

Hey that's a sweet little motor you have there. After reading the posts and looking at your pics, I was wondering if you have an adjustable thrust bar that you could move up or down a notch and see if she still makes the ahhh oOOo sounds. I know my Johnny changes tone when I trim it up at WOT.

 

[Big Jay]

Re: Motor-tone changes at wot

G'Day Waterman...

If you mean the trim adjuster pin, I've thought of that too... But it happens so intermittently that it would hard to tell if it worked.
I know it's happened on the both the closest setting to the transom and the second closest, but it was adjusted to 2 different loads. One with my 10 year old daughter in the bow, and one for my wife... basically to keep the angle right for planing and speed for their weight difference, so it's possible the engine was at the same angle in both positions .... hee hee...

 

[Watermann]

Re: Motor-tone changes at wot

You know I looked again at your set up and wonder if it's just a back pressure issue with the water flow, causing the exhaust to expel from the top port rather than the lower, which would surely change the sound. That's one of the main reasons manufacturers went to the through the prop hub exhaust set up so the water flow would help evacuate the gasses more efficiently and not have them back up to the top port.

 

[Big Jay]

Re: Motor-tone changes at wot

Hmm, that would make sense wouldn't it...

I might still heed RSchendel's advice just to be on the safe side and have a quick look @ the impeller to rule it out... but I think if it looks good, I'll be safe to chalk it up to the back-flow issue like you suggested. It sounds right and makes sense with what's happening...

 

[nwcove]

Re: Motor-tone changes at wot

are you sure the moaning and groaning isnt coming from the carb?