How long to warm up engine?

[tsutter]

Have a 1969 Merc 350 (35hp). Started it up for the first time this season with the muffs on. It took a few cranks of the key, but I finally got the thing going with the neutral throttle lever in the "up" position. I let it run with the neutral throttle lever up for approximately 2 minutes. I then tried to drop the neutral throttle lever, the motor would kill by the time the lever got half way down. It is my understanding that the lever needs to be down in order to shift gears, so does anyone have any suggestion as to why the motor is dying before I get the neutral throttle lever down?<br /><br />Could it be that the motor wasn't warmed up enough? Someone told me, I believe in an older post, that these old mercs may take 5+ minutes to warm up before being able to get going.<br /><br />Or, could there be carb / linkage problems?<br /><br />Thanks in advance.

 

[tsutter]

Re: How long to warm up engine?

bump up

 

[rickdb1boat]

Re: How long to warm up engine?

I would lean toward dirty or varnished carbs and recommend that you remove them and clean them. Make sure the fuel is good and fresh, also. I would doubt that just sitting over the winter would change linkage adjustment. It should not take 5 minutes for the motor to warm up, although those motors are cold blooded and require a bit more time before they smooth out at idle. Perhaps a minute or so, at most. What you are explaining is typical of clogged carbs and/or a float needle problem...

 

[jim dozier]

Re: How long to warm up engine?

Does this engine have a thermostat and if so is it operating properly. While I live in Florida and you are in Minnesota I would think you could get going in less than 2 minutes. I'm thinking that your fuel system needs a tuneup. Your engine may be running too lean and as a result can't handle the cold startup as well.

 

[tsutter]

Re: How long to warm up engine?

I cleaned the carb and it seemed to make a difference. When I disassembled the carb, I noticed a ton of crud in the filter strainer assembly on top of the carb. There also appeared to be a milky white substance (varnish?) on the bottom of the float bowl after the gas was drained out. I cleaned the carb and dried it with canned air. I also blew through the orifices with canned air. I put the carb back together and installed it back in the motor. The only concern I have is that I don't know if I attached the carb adequately to the powerhead. One of the two nuts that hold the carb body to the motor was incredibly hard to get to and unscrew / screw. I had to move a ton of stuff out of the way (choke solenoid, part of the cranking motor), but I think (hope) the carb is secure on that side of the attachment. <br /> <br />Anyway, I tried her out afterwards. Started up and ran it with the neutral throttle lever up, originally all the way up. But, this time, the RPMs were very high compared to pre-carb overhaul. So, I dropped the level to about halfway and let it warm up for about 45 seconds. I then put the lever down and it sputtered hard for a couple of seconds, but then gradually picked up and idled for about 20 seconds until it died out. This idle seemed a little rough. I started it up a second time. This time it started right away, and then I warmed it up with the neutral throttle lever up a bit for about 10 seconds. I then dropped the lever and this time it idled for about 20-30 seconds before I turned the motor off manually. <br /> <br />One other note: The idle mix screw was about 1 turn from seat prior to the carb overhaul. When I put the clean carb back together, I set the idle mix screw to 1.5 turns from seat. <br /> <br />One question: When running with the muffs on, I noticed alot of foamy gas exhaust coming out behind the prop. Is this normal? <br /> <br />Also, if anyone has any comments about the motor operation after the carb overhaul, feel free to voice them. <br /> <br />Thanks in advance.

 

[jim dozier]

Re: How long to warm up engine?

It sounds like you are making progress. Put the engine in the water and put it in gear (don't try to tune an engine on the muffs in the driveway they need backpressure and a load) and warm it up to operating temperature. Adjust the idle mixture (on some engines the idle screw meters fuel so unscrewing it enrichens the mixture, other meter air so unscrewing it leans the mixture, check your manual) for the best idle then enrichen it about 1/8 turn for easier starts and take off from idle. When you start the engine cold, remember to choke it and if its cold weather you may need to continue to choke it some until it warms up a bit. Get going as soon as it runs continuously, don't leave it idling to warm up.

 

[tsutter]

Re: How long to warm up engine?

Thanks for the info.<br /><br />I just did a cylinder drop test to determine if one of the cylinders isn't firing. Top cylinder only - motor starts and runs, albeit roughly; bottom cylinder only - motor won't start. When I checked the plugs - top plug looked OK, bottom plug seemed a bit dry with some black matter (specks) observed.<br /><br />Will use deep creep to decarb. Any other comments or suggestions are very welcome.<br /><br />Thanks in advance.

 

[jim dozier]

Re: How long to warm up engine?

Verify if the bottom cylinder has spark with a spark tester (cheap at an auto parts store). Make sure your spark plug is good. If the spark is good and if it doesn't fire on that cylinder then it is either fuel or compression. Hopefully when you had the carb off you did a thorough cleaning/rebuild with new parts (usually a float valve and gaskets). Did you use any solvent with the canned air? Did you pay particular attention to the idle and main jet orifices? Try squirting some premix into the bottom carb and see if it picks up, if it does you have more work to do on that carb. Good luck.

 

[propwash]

Re: How long to warm up engine?

tsutter,<br />Change them plugs with some new ones also if you have'nt already,a bad plug can cause a lot of headaches if not remedied.<br /><br /> PROPWASH.

 

[tsutter]

Re: How long to warm up engine?

Ran home at lunch to do a cylinder drop test. Tried the top cylinder only and the motor ran, albeit roughly. Tried the bottom cylinder only and it wouldn't even turn over. Checked spark - spark on both cylinders. Would do a decarb after work. <br /> <br />Decarbed the engine after work. I started her up with the muffs on and warmed her up for a minute at high idle. Then sprayed deep creep intermittently into carb throat for about 2 minutes. Then loaded the carb up with deep creep until it choked and died out. Then pulled the plugs and plied the inside of each cylinder with deep creep. Reinstalled the plugs and let sit for one hour. <br /> <br />At end of one hour, I went out and tried to start the motor back up. For about 2 minutes, the motor didn't want to turn over as it was cranking at an extremely slow beat (about once per second). Then it sputtered, then roared to life on the next crank. It idled at higher rpms than prior to the decarb. I idled the motor (medium idle) for about 10 minutes and the most god-awful smoke came out of the prop the whole time. After 10 minutes, I dropped the neutral throttle lever and the motor seemed to idle much better and smoother than it did prior to decarb. <br /> <br />However, I tried another cylinder drop test. Top cylinder - roared to life and high idle was very high rpms - much more than pre-decarb. Bottom cylinder - engine started, but was somewhat sluggish and max idle was thousands of rpms less than the max idle of the top cylinder. Would another deep creep treatment possibly help here? <br /> <br />I know my next step is to check the compression on the bottom cylinder (low compression suspected here), and will do this as soon as I can figure out how to lower my bottom cowl enough to let a comp tester fitting in. <br /> <br />Would another decarb help, or should I start looking at something else? <br /><br />I will also try some premix in the bottom cylinder. If the engine then picks up, I assume I have more cleaning of the carb to do. If that doesn't work, I know it will then be a problem with the piston / cylinder. Is this a safe assumption?<br /> <br />Thanks in advance.

 

[tsutter]

Re: How long to warm up engine?

bump bump

 

[tsutter]

Re: How long to warm up engine?

I will check the compression tonight after work with a comp tester and report the numbers back to y'all.<br /><br />I did a thumb compression check. Took both plugs out and grounded them against the side of the motor. While turning the flywheel, I noticed good blowback of my thumb for each cylinder. <br /><br />I also noticed after the decarb that my top plug was slightly fouled with some sooty black crap - fouled, but not completely covered. The bottom plug had some of that as well, but less than what was seen on the top plug. This small amount on the bottom plug was still much more than what was seen on the same plug prior to the decarb.<br /><br />Thanks again for all your inputs.

 

[tsutter]

Re: How long to warm up engine?

Compression check:<br /><br />Top cylinder = 105 psi<br />bottom cylinder = 100 psi<br /><br />They are close in range, but should they be higher? BTW, the engine was cold when I did the check. 7 turns of the key for each cylinder.<br /><br />Thanks in advance.

 

[jim dozier]

Re: How long to warm up engine?

I vote for another more thorough cleaning/rebuild of the carbs.

 

[i610288]

Re: How long to warm up engine?

I just had the EXACT same problem you have, the not wanting to run in idle, the smoking,running rough, and the ooze coming out of the exhaust.I took the fuel pump diaphram out and it had cracks in it. I rebuilt it yesterday and it roared to life, no more problems.So do that first before rebuilding every thing, it was only 14 dollars for the kit and very easy.The merc mec. said what happens is the engine floods because of the cracks,and he knew that was the problem before I even rebuilt it.Let me know.

 

[jim dozier]

Re: How long to warm up engine?

i610288 is probably on to something. If your fuel pump is connected to the bottom cylinder a leaky fuel diaphragm can inject fuel directly into the intake port and cause the cylinder to which its connected to run rich. Like he says, if it hasnt't been done already its a cheap fix. The crud you found in the carbs might be pieces of the fuel pump diaphragm.

 

[tsutter]

Re: How long to warm up engine?

Thanks for the advice folks:<br /><br />I will definately be looking at the fuel pump. When I cleaned the crap out of the filter strainer on top of the carb, it was red/tan in color. The first thing I thought was fuel tank corrosion, but when I looked at the tank, there wasn't any rust in it. I wondered what it was because there was ALOT of it (about 3/4 tsp). Although it is not idling badly right now, it could probably be better, so I hope this helps (if it is a problem). In any event I'll let you know.<br /><br />Thanks again.

 

[i610288]

Re: How long to warm up engine?

Originally posted by tsutter:<br /> Thanks for the advice folks:<br /><br />I will definately be looking at the fuel pump. When I cleaned the crap out of the filter strainer on top of the carb, it was red/tan in color. The first thing I thought was fuel tank corrosion, but when I looked at the tank, there wasn't any rust in it. I wondered what it was because there was ALOT of it (about 3/4 tsp). Although it is not idling badly right now, it could probably be better, so I hope this helps (if it is a problem). In any event I'll let you know.<br /><br />Thanks again.

you said when you put the high idle lever down it would die.Mine would do the same.It would start in high idle but run like crap and smoke real bad, when I would drop the lever to slow idle it would die every time.

 

[tsutter]

Re: How long to warm up engine?

Before I cleaned the carb, when I started to drop the high idle lever it would die. It smoked to beat all and had gas in the exhaust too. I cleaned the carb, and I was able to drop the lever and it would idle, but roughly. It still smoked too and I still had gas in my exhaust. Then I decarbed with Sea Foam Deep Creep, and I got it to idle even better - actually pretty good now. What's even more noticeable is that it doesn't smoke anywhere near as bad and I hardly noticed any gas in the exhaust water coming out of the prop after running it on the muffs for 5 minutes.<br /><br />I plan on inspecting the fuel pump to see if the diaphragm, check valves or gaskets are plugged / degraded. If so, I will rebuild the fuel pump. I then plan on taking out to the river in a couple of days (if I get the pump rebuild kit) to run her WOT - and maybe land some fish!<br /><br />I hate to sound like I'm making an endorsement here - but that deep creep stuff seemed to make a difference.

 

[i610288]

Re: How long to warm up engine?

Did you try it yet??