Merc's 4 Stroke 20 HP Carbed Motor.-

[Sea Rider]

Came to my hands a clean but neglected F20MLH motor which has been sitting well covered for the last 4 years, has not been winterized nor flushed with fresh water in it's entire life, has low run hours on it, was used to power a medium dinghy as a yacht tender.​

The fuel tank and fuel line are missing, need to get those two before attempting to start the motor. The oil was found very clean sitting right in middle of the min/max deep stick's oil levels, so good to go for some more hours work. Some things that don't quite get as there's no Owner's or Service manual that would like to know are :

(1) What's the black round rubber located at lower pan for, it's a hose that connects directly under the carb's diaphragm cover, when should it be used ?​

(2) Pressing fully in the side throttle only button releases the neutral stop to be able to gear F or R with the throttle, but when doing so the lower shift rod stays in place, doesn't move up or down a bit when tiller gearing, don't know if the long stop has seized in place the rod against the lower rod holder. Or this motor must be running for the shift rod to work ? All for the moment, thanks in advance...​

Happy Boating

 

[bwkre]

When using the throttle only button there should be no movement of the shift rod. It allows you to operate the throttle through its full range while the motor is running, without engaging a direction.

 

[Sea Rider]

When using the throttle only button there should be no movement of the shift rod. It allows you to operate the throttle through its full range while the motor is running, without engaging a direction.

So, in what moment is the shift rod being seen engaging up or down, there isn't a side shift lever on this motor as to engage F or R. The motor isn't running at the moment, need to check several things before first start.

Happy Boating

 

[bwkre]

The tiller rotates in both directions from neutral, depending on what direction you want to go. As you rotate the tiller it will automatically shift into gear and as you rotate further it will increase rpm. Same applies in the other tiller direction except you will engage the opposite direction. Everything is done through the tiller.
The push button allows you to increase rpm without engaging a direction. But doing it with the motor off and rotating the tiller will still operate the accelerator pump, dumping fuel in the carb.

Takes some getting used to but it's a complete one hand operation. You can test this with the motor off but be sure to rotate the prop to allow the lower unit to engage.
Also note that the tilt unlock is automatically done when you shift to fwd. It can not be unlocked manually. So if your racing to shore to beach your boat make sure you keep the motor in fwd when you turn it off, or you won't be able to lift it! Scrape scrape.
I went from a 61 evinrude to a 2021 merc 9.9 tiller shift. Took some getting used to.

 

[Faztbullet]

The rubber button is the carb primer

895124 Mercury Mariner 8-20 Hp 4 Stroke Outboard Priming Pump​

 

[Sea Rider]

Thanks both,

Last time I did so as per your explanation the tiller was very stiff to rotate, should it be a smooth engagement say Forward while throttling ? If, so definitely need to lube all the associated mechanism. This motor has been sitting too darn long unattended as the majority of my boating club's motors. Does anyone has a PDF copy to share ?

Happy Boating​

 

[bwkre]

If you goto the Mercury website, support page, you can download the owners manual for your motor. Or one for the same model of a different year. Explains how the shifter / tiller works. Manual says not to shift reverse unless the motor is running.

 

[Sea Rider]

While throttling from N to F there was No Joy, the shifter mechanism seems way stuck frozen while can throttle all you want till throttle stops.

The Merc's Support Page :

Mercury Marine - A Worldwide Leader in Marine Propulsion | Mercury Marine

Manufacturers of outboard motors and MerCruiser inboard engines, with over 4000 dealers in the United States.

www.mercurymarine.com

Shows no Owner's Manual to download...

Happy Boating​

 

[bwkre]

try this,

| Mercury Marine

Manufacturers of outboard motors and MerCruiser inboard engines, with over 4000 dealers in the United States.

www.mercurymarine.com

 

[bwkre]

edited

 

[Sea Rider]

Thanks,

Merc will charge you for a printed copy of the Owner's Manual : http://publications.brunswick.com/product-p/ob-om.htm is there somewhere a PDF version to download ? Update : Wile the throttle remained at N throttle shifted to F and nothing happened. Must the motor be running in order to gear **** it to F or R from N ?

Happy Boating​

 

[Faztbullet]

https://boatworld.ee/assets/Uploads/PDF/Mercury/Kasutusjuhendid/Mercury-paeramootori-kasutusjuhend-15-20-hj-ENG.pdf

 

[bwkre]

Thanks,

Merc will charge you for a printed copy of the Owner's Manual : http://publications.brunswick.com/product-p/ob-om.htm is there somewhere a PDF version to download ? Update : Wile the throttle remained at N throttle shifted to F and nothing happened. Must the motor be running in order to gear **** it to F or R from N ?

Happy Boating​

Shifting fwd should move the linkage, no need to be running. Manual states NOT to shift in reverse with motor off.
Could be the "throttle only" button stuck. Guess you will have to dig into it further. good luck.

 

[Sea Rider]

Shifting fwd should move the linkage, no need to be running. Manual states NOT to shift in reverse with motor off. Could be the "throttle only" button stuck. Guess you will have to dig into it further. good luck.

The throttle only button works as intended, tomorrow will check with a similar branded motor if the throttle grip and the shift rod works together well... Thanks.

Happy Boating​

 

[Sea Rider]

Checked same with other similar Merc motor and No Joy. While the throttle remained at N was not possible to make it to gear F, when the throttle only button was pushed fully in was possible to throttle to any position, but the shift rod stayed frozen in place. Both similar motors can't possibly have the same issue. Will need to call the local witch doctor to exorcise them both....

Happy Boating​

 

[bwkre]

What do you mean "not possible to make to gear F". Just rotate the tiller, it click and goes in F then you can increase throttle . My 9.9 dose not need to rotate crank or prop to make F. just turn tiller to shift. And it is recommended method to be able to tilt motor when off. Just cant do R unless running.

 

[bwkre]

The way mine works & what the tiller looks like

 

[Sea Rider]

What do you mean "not possible to make to gear F". Just rotate the tiller, it click and goes in F then you can increase throttle .

Yep, tried same as per your description and video, when rotating both grips fron N to F there's no clck whatsoever. Have not tried to rotate both grips that hard, could break something in their shift mechanism and those are not my motors to play with aggressively

Both doesn't have more than 50 run hours on therm from out of the box, throttle grips are impeccable clean. Will try to get a fuel tank and hose to start the motor and check if gears F or R from N while rotating the throttle grip ? Thanks again, highly appreciated!!

Happy Boating​

 

[Sea Rider]

Meanwhile can find a donor portable tank and hose to startup the motor read courtesy of FB the extensive Merc's Owner's Manual twice. The only written indication states to gear F or R from N at idle speed. In most motors while OFF you can attempt to fully engage F or R from R, sometimes will be possible to do so, most times won't unless aggressively forcing the gear lever F-R from N with a high risk of breaking it or even screwing something inside the gearbox. Motors must be geared while ON.

The PDF OM lacks 2 tech important points not stated by the manufacturer such as :​

The Mystery Button (?) which is a primer button isn't mentioned nowhere on the OM literature, so the new owner won't know what's all about for or when to use it properly? No wonder there's a lot owners having startup issues and unwanted delays due to poor startup information available in the Manual.

Doesn't provide a Prop Chart at all, maybe Merc is happy delivering such 4 stroke 15-20 HP motors with over propped 3 blade 10 pitch ones as only alternative...

Happy Boating​

 

[Faztbullet]

Its on page 66 and should have the decal on cowl. Not rocket science, pump up bulb, pull choke. pump primer button 3 or 4 times and rip stater rope. Just like a chainsaw.