Over prop? How to know?

[jlh3rd]

actually, I was responding to dingbat's post....as kindof a question...

so I did....

Nope.....the water creates back pressure in the cylinders.
Search the forum for how many times people say the motor runs "great" (on a hose) until they put them in the water...

Different motor, but mine idles in neutral at spec, ~800-850 in the water and 1200-1250 on a hose. Dropping it in gear reduces another 100 RPM or so

Read the specifics of your motor in the manual.

ok...I did...here it is........doesn't matter...

 

[tywiesz]

so I did....

ok...I did...here it is........doesn't matter...View attachment 374467

I see, good point of yours, my is in the water, so your photo says nothing like idle rpm in a gear

 

[jlh3rd]

there is no idle rpm in gear specification for my engine....those are the only ones.....it doesn't matter for mine....it is ECM controlled...

and..here is an 05-11 merc outboard repair manual.....
the lower hp engines have separate neutral/trolling speeds..they are not ECM controlled..
the higher hp and ECM controlled engines does not matter...one idle setting...

I'm sure your honda is not ecm controlled....

 

[QBhoy]

You’d imagine the IAC controls the idle rpm. The IAC of course, often, is controlled by an ecu.

 

[jlh3rd]

well...yeah...ECM's control engine parameters through modules that operate solenoids that open close, turn on, off valves, switches...and assorted mechanisms.....

 

[dingbat]

well...yeah...ECM's control engine parameters through modules that operate solenoids that open close, turn on, off valves, switches...and assorted mechanisms.....

Please enlighten me on how the ECM adjusts the individual air /fuel mixtures of the carbs?

Back pressure on the exhaust affects the flow of air though the motor. Has direct affect on the air to fuel ratio. Back pressure is not equal in each cylinder, therefore each carb is adjusted separately with the engine in the water to compensate for the back pressure.

In this case, Honda requires the carbs to be synchronized using a vacuum gauge to within plus or minus 0.5Hg or better. Reason why they don’t need idle adjustments in the water

See carb synchronization procedure page 7-12

https://www.virtualware.nl/wp-content/uploads/Honda-carburation-manual.pdf

 

[QBhoy]

Please enlighten me on how the ECM adjusts the individual air /fuel mixtures of the carbs?

Back pressure on the exhaust affects the flow of air though the motor. Has direct affect on the air to fuel ratio. Back pressure is not equal in each cylinder, therefore each carb is adjusted separately with the engine in the water to compensate for the back pressure.

In this case, Honda requires the carbs to be synchronized using a vacuum gauge to within plus or minus 0.5Hg or better. Reason why they don’t need idle adjustments in the water

See carb synchronization procedure page 7-12

https://www.virtualware.nl/wp-content/uploads/Honda-carburation-manual.pdf

I presumed it was a 2011 motor. Might be wrong. But if it is..a Honda 90 that age or anything after 2007/08 will be fuel injected I’m sure.

 

[jlh3rd]

Please enlighten me on how the ECM adjusts the individual air /fuel mixtures of the carbs?

Back pressure on the exhaust affects the flow of air though the motor. Has direct affect on the air to fuel ratio. Back pressure is not equal in each cylinder, therefore each carb is adjusted separately with the engine in the water to compensate for the back pressure.

In this case, Honda requires the carbs to be synchronized using a vacuum gauge to within plus or minus 0.5Hg or better. Reason why they don’t need idle adjustments in the water

See carb synchronization procedure page 7-12

https://www.virtualware.nl/wp-content/uploads/Honda-carburation-manual.pdf

word salad.....
why do people like you get on the internet and just wanna argue..huh?
I did exactly as you said.....went out to my boat.....got my 2021 merc. 115 hp CT's manual......looked up, took pics of, and posted here the official and all idle specifications....there are NO specifications for idle in the water, in gear.....ok?.......maybe your motor is...I don't know, and I dont care.....

and I said I have no idea about his honda!.....

If I have to explain to you how ECM's work....how computer engines work....
and how they are controlled......I....can't.....help......you....

christ!

 

[jlh3rd]

furthermore....I had an '87 Monte Carlo with a rochester 4bbl. carb that was computer controlled using throttle body injection ....CONTROLLED by the ECM.....
that's how ecm's can control a carb......
jesus...

 

[jlh3rd]

not doubting you, just ask'n......I fully understand water exhaust creating back pressure at the exhaust manifold possibly affecting idle....
My motor is a 2021, .computer controlled idle......I have the all the manuals and paperwork that came with the motor....Curious, so I'll see....
I have no idea about his honda.....

tried to be respectful to you....but...nooo...
that didn't work....did it....

 

[QBhoy]

word salad.....
why do people like you get on the internet and just wanna argue..huh?
I did exactly as you said.....went out to my boat.....got my 2021 merc. 115 hp CT's manual......looked up, took pics of, and posted here the official and all idle specifications....there are NO specifications for idle in the water, in gear.....ok?.......maybe your motor is...I don't know, and I dont care.....

and I said I have no idea about his honda!.....

If I have to explain to you how ECM's work....how computer engines work....
and how they are controlled......I....can't.....help......you....

christ!

The 115 merc ct is definitely controlled idle by ecu. No doubt about it. I have one of them. Great engines. Mine sits about 650-700 ish. But they can also raise their idle or in gear idle speed if they need more charge to the battery. Very clever

 

[jlh3rd]

yeah...just trying to help the OP....then things get...twisted.....
it was stated that OB's have specified idles in their manuals for in gear, in water, in neutral, etc....the answer is not necessarily.....that's the truth....

 

[QBhoy]

yeah...just trying to help the OP....then things get...twisted.....
it was stated that OB's have specified idles in their manuals for in gear, in water, in neutral, etc....the answer is not necessarily.....that's the truth....

Would say you’re likely right there. Not as specific to give the various states I’d say.

 

[Scott Danforth]

furthermore....I had an '87 Monte Carlo with a rochester 4bbl. carb that was computer controlled using throttle body injection ....CONTROLLED by the ECM.....
that's how ecm's can control a carb......
jesus...

uh.... carb and TBI are two different things

the 87 G-bodies came with either a TBI V6 or a carbed V8 or TBI V8 depending on sub-model. however there was no computer for the carb'd version

 

[airshot]

My recomendation is to start with checking everything accurately !! This means to stop guessing....you need to have accurate guages or soon you will have a basket of parts from a blown up engine. Start with knowing for surevyour tach is good!! Know for sure what the wot rpms for your motor....know for sure what the idle speed shoukd be ..in the water!! Guessing will cost you big bucks in the end.....

 

[jlh3rd]

uh.... carb and TBI are two different things

the 87 G-bodies came with either a TBI V6 or a carbed V8 or TBI V8 depending on sub-model. however there was no computer for the carb'd version

scott...respectfully...

It was a 1987 chevy Monte carlo SS...with the high output 305....with a rochester 4bbl carb with a mixture control solenoid mounted at the top of the carb....it was considered a hybrid bridge between a real carb and fuel injection...It worked the two idle needles..
I used a rochester carburetor manual to overhaul it....
....the car was OBD1....with a computer.....I don't know the degree of control that the computer had over the two injectors.....but they were not mechanical, they were controlled by the computer.....
Any computer in any car is also know as the ECM......commonly speaking...which is what I am doing......

 

[jlh3rd]

it was electronically controlled and it was a carb...

 

[jlh3rd]

just in case it isn't clear

 

[jimmbo]

scott...respectfully...

It was a 1987 chevy Monte carlo SS...with the high output 305....with a rochester 4bbl carb with a mixture control solenoid mounted at the top of the carb....it was considered a hybrid bridge between a real carb and fuel injection...It worked the two idle needles..
I used a rochester carburetor manual to overhaul it....
....the car was OBD1....with a computer.....I don't know the degree of control that the computer had over the two injectors.....but they were not mechanical, they were controlled by the computer.....
Any computer in any car is also know as the ECM......commonly speaking...which is what I am doing......

You are referring to the E4ME Q-Jet
It had nothing to do with the Idle Needles, those were still on the Throttle Body, usually hidden by covers.
The Computer was controlling the Primary Metering Rods using a Solenoid, in response to what the O2 Sensor(s) was telling it

 

[jlh3rd]

ok... the two primary metering rods.....that was pulled from memory 27 years ago, i'm not perfect...
I said it was computer controlled by an ECM ...It is
I said it was still a carb....it is
I said it has a solenoid that controlled mixture....it does...
I said it was considered a hybrid crossover from a standard carb to a throttle body injection.....it is
It has a throttle body........with fuel entry modulated by pulsed metering rods operated by the mixture solenoid ( 10 times a second). Just like a pintle in a modern fuel injector..except vacuum being used instead of fuel pressure...and much more than 10 times a second.....
...it's a hybrid.....

I've got the manual....I rebuilt the carb....back in the day......
5 outa six from memory....not too bad.......