1977 Mercury 115 rebuilt and video for idle run, suggestions please

[tavacska]

https://youtu.be/14KXTDQXjQE

Hi, I posted a video for the idle run of the 1977 mercury 1150.

I have concerns about the motor.

1. The water tail used to be very good. A very strong water stream. However after taking off the lower unit and put back again. It runs poorly as the video shows.
After seeing that, I took off the lower unit again. I made sure the water line to the engine is tight. And the I blow the water tail line and confirmed it is not blocked.
The water pump was rebuilt a month ago and worked perfect.

2. Is there any water in the exhaust part. I didn't touch the exhaust part so not sure and don'd know the symptoms of water leakage.

3. Never own an outboard before. So I don's know if the motor runs strong in the video. It can not start at the idle speed below 1000 rpm. I have to stretch the throttle cable to start it and then move back to idle speed. It can idle at 800 rmp for quite a while. But it vibrates a little bit and I really don't know if it's normal.
Should I have a visit to the mechanic because I really don't know what does the tuned motor runs like.

Thanks again for the help from the forum.
You are the best.

 

[merc850]

Replace that rotted wire that runs from the starter to the front support frame. You use the cold start lever/button on the control box to raise the idle to start then put it down to run, the motor has to have the low speed needles adjusted running in water in F at 900 rpm start at 1 1/2 turns out then adjust each one in or out to achieve smooth running. That screw with the red cover that the dist. is hitting is the adjustment for the idle speed you turn it in or out to change the setting. It sounds pretty good so far.

 

[tavacska]

Thanks for the advice.

As for the control box, I saw many videos about the cold start lever. My control box doesn't have that lever, but a button which engage only the throttle cable without the gear cable. In that case, how do I "cold start" with that control box?

 

[flyingscott]

The button replaces the second lever. Push the button in so you get throttle only function then push the throttle forward a little and start the motor. Use the choke normally. It will take a little trial and error to set the throttle correctly for starting without revving the motor to much.

 

[tavacska]

Got it. Thank you.
Is this "cold start" a very normal situation for the mercury inline 6? I read someone says it's quite normal for this kind of machine. But others says they shouldn't be unless there is something imperfect with the motor.

 

[racerone]

???-----Not sure where your advice is coming from.--------------You must advance the throttle slightly so that throttle plates open a bit.------Then you must engage choke during cranking until motor fires.----If motor falters then you bump the choke button momentarily untill motor warms.-----Do not let motor rev wildly in nuetral.------Make sure those plastic choke plates are not warped and that they seal properly.------If you continue to have starting problems I would install an OMC electric primer on that Mercury.----That virtually eliminates the " hard to start issue " on that motor.

 

[tavacska]

???-----Not sure where your advice is coming from.--------------You must advance the throttle slightly so that throttle plates open a bit.------Then you must engage choke during cranking until motor fires.----If motor falters then you bump the choke button momentarily untill motor warms.-----Do not let motor rev wildly in nuetral.------Make sure those plastic choke plates are not warped and that they seal properly.------If you continue to have starting problems I would install an OMC electric primer on that Mercury.----That virtually eliminates the " hard to start issue " on that motor.

So much info, thanks.

I will have a look at the electric primer.

But you are saying advance the throttle until the plates open. Does that mean, it passes the max advance position? It already scare me a lot sometimes at max advance position. The motor roars so much when it starts.

The manual says no RPM more than 1000 when water hose connected, it will fly away. So when I open the throttle plate a little, it starts with extreme RPM. Should I pull back to idle right away? Or should I just wait the motor to warm up a little bit?

 

[racerone]

Throttle plates need to open a LITTLE bit and you have to experiment with how much.----It is not good for a motor to roar away in nuetral

 

[Chris1956]

The gratings above the antiventilation plate is the exit for most of the cooling water. Your motor looks to pump water fine. Your telltale maybe clogged. That is very common.

A 1977 motor will have two choke plates on the top two carbs. Those should close when the choke button is pushed.

Using the throttle only button, advance the throttle 1/2" and try to cold start. She can run at 1200-1500 RPM when warming her up.

Idle speed on the flusher with the motor warm, can be 1000RPM. It will be less in the water.

FWIW, I thought she sounded fine. You might check the idle pickup and max spark advance and see what they are. Idle pickup timing should be 4-6* BTDC. Max spark advance is 21*BTDC. I would purchase a service manual before adjusting anything, as link and synch is important and you do not want to mess it up.

 

[tavacska]

Chris,

Thanks a lot. They are the exact and correct info I have learned and followed. I have a book manual dedicated for 1977 the motor. But I thought some specs in the book are too conservative. I need to know the realistic experience ways and numbers that I can follow. Like the 1200-1500 rpm you mentioned.

Following the service manual, my motor's the primary pickup is 5 BTDC. Max spark advance is 20 BTDC(someone from youtube says 20 BTDC is better for nowadays gasoline, which I am following).

At the idle speed of 800 rpm-1000 rpm with flush, the idle pickup timing is 4-5 BTDC, which troubles me a lot before. This is because some info from youtube says, it should be around the TDC, or 0-2 BTDC. And the manual as I read doesn't mention the idle pickup. I can never reach that point 1 BTDC, before the motor stops. Now I am more confident now that the motor is pretty healthy.

One exception about the manual is the synch of the crank and the distributor. I tried to follow the manual, putting the arrow half tooth clockwise ahead. But I didn't find the 4-6 BTDC and 21 BTDC. However, the cover of distributor pulley has a dot at the edge. That dot is aligned with the dot from the cast housing holding the distributor. And I aligned the position pointer to TDC at the same time. The link and synch is perfect by doing that. I guess, since I got the 5 BTDC and 20 BTDC correct. I must have done the right way. Hope I am right. I figure this out myself after trying a lot of times.

I can always start the motor when I set the distributor half way between primary pick up and max spark advance before it could open the throttle. The only thing it scare me is when it starts, it roars and spits out with huge fume. I guess the fume is caused by several cranking failure before it starts. I will try to find the points of 1200- 1500 rpm and start it more smoothly.

Thank you.

 

[tavacska]

Yesterday, I watched a video teaching how to unload the boat by single one person.

The boater has the same kind of remote control. He pushed the button, pushed the throttle, then start, 1-2 sec later, pulled back to upright.
Now I accept that this is a normal regular procedure, but not a sign the motor needs maintenance.

 

[merc850]

I'd like to see a motor run at TDC setting, the plugs would be firing and the piston could go either way or not move at all.

 

[Chris1956]

Tavacska, Idle pickup timing is when the distributor finger is about to open the carb (touching the carb lever and taking up all slack), but the carbs are still closed. That is when the timing should be 4-6* BTDC.

Have you set the timing pointer, using the .464 inches before TDC? That should be the first step. Second step is to make sure pulley on distributor points to dot (maybe motor has 3 dots), and then install the belt. Timing pointer will point nearly or exactly to the TDC mark on the decal.

Next remove spark plugs 2-6 and install them into the wires and ground their bases. Now advance throttle until carbs are ready to open, crank motor by jumpering solenoid, and measure timing. Rotate brass collar (need 5/16" open wrench to loosen set screws) to set idle pickup timing correctly.

Now advance throttle to max and check timing. Use max spark advance set screw to set it to 21*BTDC. Set throttle stop to stop the carb opening just short of their stops.

Now install all spark plugs, install flusher, turn on water and set idle stop screw (may need to adjust throttle cable) until motor idles at about 950-1000 RPM. Do not adjust brass collar. Idle timing is not specified and not important. Only idle pickup timing is specified.

When cold starting motor, you should only need a little bit of throttle. Try to get her to run at 1200-1500 RPM when she starts cold. That is all that should be needed.

 

[tavacska]

Chris,
I misunderstood your meaning of idle pickup. I thought it was the timing when the motor runs idle speed. It was mentioned as primary pick up in the manual. I got you now.

I have the well set timing pointer following the .464 rule.

I tested with a timing light, that the idle pickup is 5 BTDC, and the max spark advance is 20 BTDC.
Actually, I didn't have to adjust the brass collar and max advance screw. Their original setting works good for my settings. So, I think the link and timing syncs is correct.

I didn't care or remember where the pulley arrow points to in detail though. My theory is the pulley has 24 teeth. One teeth miss will be 360/24=15 degree. If I did the timing belt wrong, I can not get the 5 BTDC and 20 BTDC very easy.
Please correct me if I am wrong.
( the above I talked about is, I think the setting of timing of my motor may be correct fortunately)


What always confuses me a lot is the mechanics and theory of the relationship between the timing and RPM.

1. Why you have to push the throttle when cold starting.
2. Why push the throttle before opening the throttle plate can increase the RPM? (since the air inlet every cycle should be the same).
3. Is it timing of ignition or the composition of air and fuel that change the RPM?

For my limited understanding, you push the throttle before opening the throttle plate, the air inlet is the same in each cycle. But, you also changes the ignition timing more advanced. The more advanced, the more moving speed of piston because of more resistance of combustion.(very confusing, just like a spring, the stiffer, the more frequent).
But why and why, the increase of RPM can help the start of the motor? Because the increased RPM can suck in more fuel in each cycle (inlet air the same, I guess)? If in that case, can I just enrich the idle mix for the start as long as it won't affect the running?

I think I may never figure it out by myself.

 

[tavacska]

And one more question.

There is water, easily felt by hand in the upper hole exit.
Is it normal? I remembered, the combustion exhaust and water way at that height should be separated.
I changed the gasket where the power head comes off. But never touch the combustion room.

 

[merc850]

The spark (distributor) advances first to max 20* this increases rpm to a certain level then the collar moves farther to open the butterflies to full open position - this is so the spark will be at the proper time for the air/fuel mixture to ignite; the open butterflies add more energy to the cylinder to increase horsepower. This system gives maximum power with efficient fuel consumption. The cold start advance is to set the idle speed higher to overcome the "cold" cylinders; you use the choke at the same time to give it more fuel to boost the available fuel molecules for ignition.

 

[merc850]

Water cools all the exhaust areas and comes out of the "holes" you are looking at.
Study this cutaway the exhaust goes down the "tube" and water surrounds it.

 

[tavacska]

This picture is awesome.
Thanks.

 

[Chris1956]

Those square holes at the base of the powerhead are idle relief ports. In theory, if the motor is in neutral and in the water, the exhaust may not have enough pressure to push the exhaust out the prop. The square holes relieve that situation.

In practice, water will exit those ports whenever it feels like it. On my motor, water routinely came out on the flusher, in the water in gear, and probably other times. I would not worry about it.