1989 50hp Johnson turning 6500 rpm

[Toad Snatcher]

First question is will the high rpms cause my volt meter to read 16v?

Second question is should I change the 11 3/4 x17 prop to a 11 3/4 x 19 to get the rpms back into range?

 

[boobie]

Re: 1989 50hp Johnson turning 6500 rpm

1st ? = yes

2nd ? = Check your tach before you do any prop changing.

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

One more question, would the high rpms and high voltage cause my fly wheel to get really hot? Thanks for the response.

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

Here is a pic while running.

 

[WernerF]

Re: 1989 50hp Johnson turning 6500 rpm

The tach can be checked with any musical instrument. At 5,550 rpms the engine sounds with an F# tone.

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

I know this model does not have a voltage regulator so what voltage output should I see at 5,500 rpms?

 

[WernerF]

Re: 1989 50hp Johnson turning 6500 rpm

16V is not good, but pretty normal for rectifier-only charging system with modern batteries. The old non maintenence-free batteries were able to sink an amount of current, but modern batteries are not.
The quick solution is to observe the voltage and apply an electrical load (e.g. position lights) when the voltage rises above ca. 15V.
Best is to convert to regulator.

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

Do you think this would cause my flywheel to get so hot?

 

[WernerF]

Re: 1989 50hp Johnson turning 6500 rpm

No, I don't think so. The flywheel doesn't touch anything but the crankshaft. How hot does it get?
With a proper working cooling system the engine reaches 140...150F. Under the cowling everything will get a similar temperature after some time.

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

I pulled it out of the water the other day, drove 5 minutes home from the lake pulled the cowling off and it was still almost too hot to keep your hand on.

 

[F_R]

Re: 1989 50hp Johnson turning 6500 rpm

As somebody already said, 16V is pretty normal. In theory, not good, but there are thousands of motors running around that way. Including mine.

I'm not sure of the technical reason, but flywheels do get surprisingly hot.

 

[nwcove]

Re: 1989 50hp Johnson turning 6500 rpm

The tach can be checked with any musical instrument. At 5,550 rpms the engine sounds with an F# tone.

....i can check a tach with a tuba???

 

[WernerF]

Re: 1989 50hp Johnson turning 6500 rpm

Yes you can, not very efficient though. But the tuba has the avantage that the reference tone would be in the right octave and you don't have to make any octave shifts by ear.
I've seen a virtual piano keyboard on an iphone. Or your daughter could play an F# on her recorder flute. Or you can play an E tuned blues harp on the second step. Anything that can give you a tuned F# reference. Or you are blessed with a pefect pitch.
I used a guitar tuner.

 

[nwcove]

Re: 1989 50hp Johnson turning 6500 rpm

Yes you can, not very efficient though. But the tuba has the avantage that the reference tone would be in the right octave and you don't have to make any octave shifts by ear.
I've seen a virtual piano keyboard on an iphone. Or your daughter could play an F# on her recorder flute. Or you can play an E tuned blues harp on the second step. Anything that can give you a tuned F# reference. Or you are blessed with a pefect pitch.
I used a guitar tuner.

with all do respect.....i want some of what yer smokin!!

 

[daydreamer1252]

Re: 1989 50hp Johnson turning 6500 rpm

All very interesting and cutting edge.....for me I'll use the tach....Thanks....

 

[Toad Snatcher]

Re: 1989 50hp Johnson turning 6500 rpm

Seems to me that the high voltage from the charging system could cause wires to get too hot. My mechanic wants me to re-prop to get the rpms down.

 

[fishfeatures]

Re: 1989 50hp Johnson turning 6500 rpm

I have a recent thread here of where all my gauges stopped working one day all of a sudden. I too noticed high volts on the voltmeter of around 16V. Only had a rectifier on my 1990 60hp , but general consensus was to install a regulator instead which I did, i am going to put in new gauges soon so hopefully that's my prob solved. SO i reckon you too need to go to a regulator before any thing bad happens.