Just wondering about idle on 130 BETO

[Speedcop]

Hi All,
My 1999 Yam 130 BETO runs fine, starts first time every time!
A WOT, it runs at 5,700 rpm with a 19’ prop. All seems ok.
I was just wondering, when I start from cold, (choke off as soon as it fires), the idle sits at 800 rpm, but as it warms up to operating temp while idling, it drops to 750 rpm. Just wondering if this is normal, due to electronic management, or could there be something else at play? The idle jets are set at 9/10ths turn from closed.
Just wondering, or should I go with the old saying: “IF IT AIN’T BROKE DON’T FIX IT!”
I would appreciate thoughts or comments from the forum.
Thanks Guys.

[99yam40]

You might monitor the Idle timing at cold start up to see if it advances a little until the motor warms up.
I know my 1999 C40TLRX does, but it is a prime start model not a choke model

[boscoe99]

I vote for "it ain't broke so don't be fixing it".

As noted, if you just want to see if timing is being changed as the motor warms up put a timing light on it and see.

Many would love to have your "problem".

[rodbolt17]

I will third the "aint broke don't fix it.

don't know about the NON US market 130 but the US market 130 had NO provision to electronically alter ign timing based on engine temp.
it could at OVER temp cause an ign misfire and RPM reduction.

most likely its still slightly rich at cold start and leans out a bit once warm.
on a carbed motor its normal.

[Speedcop]

Just wondering.

Hi 99yam40, boscoe99 and rodbolt 17.
I think Rodbolt has the most likely answer…
“Most likely it’s still slightly rich at cold start and leans out a bit once warm.
On a carbed motor its normal”.
I checked the timing with timing light, and there is no change once it warms to operating temp.
The motor is a carbed model and has the manual choke fuel enrichment.
So I guess I’ll stick to:- “IF IT AIN’T BROKE DON’T FIX IT!”
Once again, thanks so much for the valued advice. It is highly appreciated.

[boscoe99]

I be confused.

On a carbureted motor, with the choke not being used, the air/fuel mixture should be on the lean side when the motor is cold. The fuel is not being vaporized sufficiently for the amount of air that is entering the motor for a correct mixture.

So, a choke or a prime start device is used to add extra fuel to richen the air/fuel mixture until the motor warms up.

If it were rich when cold, why would a device be used to supply extra fuel to the motor at that time?

[99yam40]

could be that the original choking procedure dumps extra fuel into the crankcase and just takes time to get it out to normal mixture hitting the cylinder.
Just a thought

[rodbolt17]

contribute the EXTRA fuel a manual choke can dump when bypassing the normal circuits PLUS the unburned oil and fuel from the last shutdown it can remain a tad rich and smoke badly at start up.
both conditions are rather normal.

most tachs wont reliably monitor 50 RPM changes either.

[Speedcop]

Just wondering.

Hi again Guys.
I agree again with Rodbolt. (BTW the revs were measured with a professional meter. Revs ,dwell volts etc etc.)
I normally run the motor dry when finished boating. It does seem to smoke a bit more on start up the next time. I figure this is due to the running dry process as there must be residual oil left in the cylinders.

99yam40, I agree it could also be due to the choke giving excess fuel momentarily.

Boscoe99, why a device would be used to supply extra fuel confuses me as well, but my motor won’t start without momentarily using the choke on cold start.
Anyhow it runs beautifully, so I ain’t gonna fix it cause it ain’t broke.
Thanks to all for your valued input.

[99yam40]

Just one more thought from me,
running a multiple carb motor until it dies after unplugging the fuel line does remove some of the fuel from the carb bowls but it does not remove it all.
Then what is left in the bowls evaporates quicker than a full bowl would, still leaving residue in the bottom on the bowl.

And when running at the last some of the cylinders are running lean due to all of the carbs will not run out of fuel at the same time due to gravity and what is in the lines running to them. Top carbs will run out before the bottom ones.
It is best to drain the bowls via the drain plugs if motors are to be set up for a long period of time to get it all out

[Speedcop]

Just wondering cont...

Hi 99yam40, thanks for that input!
To be honest I have never thought of it like that. You are 100% correct.
A full bowl would be better, and it makes sense to drain the carbs from the drain plugs at the bottom of the floats for long storage.
I guess one should also empty the motor mounted fuel filter as well when the motor is going to stand for a long period. I usually put ‘Ring free’ in the fuel tank.
I always learn something valuable from the experts: yourself, Rodbolt and Boscoe. Thank you all kindly.