Runs on muffs, not on water

isnms

Seaman
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May 15, 2004
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51
'70 Mercury 1150, sn: 2840981 <br /><br />On dry land with muffs, I can crank it, and it cranks easy, let it warm up, return the advance lever to normal and it has a nice idle.<br /><br />I take it to the lake and it's difficult to start. It will start eventually, just have to prime the top carb with some fuel. It will not stay running when I return the advance lever to normal.<br /><br />Spark is good and plugs are new, trigger is good, fuel getting to the carbs is good, firm pump bulb<br /><br />I, also, still need to check compression.<br /><br />I had this ready to post then found some related information. I will need to check these things out but I wanted to get my post up anyway.<br />
Clams Canino thread:<br />Timing and Sync of Merc Inlines (to 1988)
Laddies & Clams Canino post:<br />...Usally a motor that will idle on a hose but not in the water needs carb attention first, some have a lower main seal out,...<br /><br />...If it can idle on the muffs the reeds (and blocks) are probably good enough to run right...<br /><br />...If the motor is overpropped for the boat it'll do the same thing, ditto if the carbs are too lean, or the timing and sync is off...<br />...but it's more likely to be mis-adjusted or overpropped as opposed to having worn out reed blocks.<br />
Ed Mc. post:<br />A dyno may not simulate the backpressure of sitting in the water. You can try increasing the idle speed. If there's a mixture adjustment on the carbs, you'd want to adjust the needles to richen the mixture (CCW).<br /><br />How about a compression check, has anyone done that?<br /><br />You also may have issues with the upper or lower crank seals; loss of crankcase vacuum will affect idle quality, especially in the water.<br /><br />Has anyone checked the plugs for water after one of the 'dying' incidents? If you find water on the plugs you could have leaks from the exhaust manifold or gaskets.
Trent post:<br />Time to remove the carbs and install overhaul kits. Clean very well with carb cleaner. And when your done........Clean AGAIN!!<br /><br />Your engine runs good on the "hose" because it does not have back pressure on the exhaust system.
So maybe I already have the answer, once I check these things.
 

tashasdaddy

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Re: Runs on muffs, not on water

you are on the right track.
 

isnms

Seaman
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May 15, 2004
Messages
51
Re: Runs on muffs, not on water

Battery fully charged.<br />Set throttle stop for proper adjustment.<br />Top two carb idle mixture were 1turn out, bottom was ½ turn out. Set all to 1 ½ turn ccw.<br /><br />Compression, warmed up, psi:<br />1 – 120<br />2 – 125<br />3 – 125<br />4 – 120<br />5 – 135<br />6 – 120<br /><br />Starts with one crank on muffs. Tell tale water about 120°F. <br /><br />Took it to the lake. Still will not start on the water. :( <br /><br />Came back and adjusted - throttle pickup 4°, maximum spark advance 21°, and secondary throttle pickup. I don’t know that I changed these since I had to loosen them to set them, but they are set to spec now.<br /><br />The other adjustments – idle stop and idle mixture – have to be adjusted with the engine running on the water.<br /><br />Starting procedure:<br />• motor tucked under<br />• primer bulb firm with a couple extra pumps.<br />• warm up lever up<br />• engage enrichener while starting<br />Works fine on muffs.
 

Gold Bear

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Sep 26, 2001
Messages
224
Re: Runs on muffs, not on water

Isnms,<br /><br />Try this.<br /><br />Set idle speed adjusting screws to 2 turns open, from lightly seated.<br /><br />On the hose, set the idle speed adjusting screw so the engine (after it warms up) runs at a fast idle (say 1,200 rpm's). Take it to the lake, use the "usual" starting proceedure. It should start relatively quickly. If after it warms up at the lake, if you find that it still idles to fast, adjust the idle screw down to at least 1,000 rpm's, 800 is better if it will do that.<br /><br />While at the lake, if it does not want to start right up after steeing a while (setting for 30 minutes or so) then you may have to open the idle screws another 1/4 turn or so.<br /><br />Good Luck,<br /><br />Gold Bear
 

tashasdaddy

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Re: Runs on muffs, not on water

when starting my 1350, i hold the choke until it firsts starts. when real cold i turn it over a couple of times and repump the bulb until completely hard. they like a lot of gas to start cold.
 

isnms

Seaman
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May 15, 2004
Messages
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Re: Runs on muffs, not on water

Gold Bear & tashasdaddy, thanks for the tips.<br />I have some more recent info from Monday to add:<br /><br /><br />Success!! It started on the water. It seemed to run a bit rough. I adjusted the idle mixtures but they are still about 1 1/2 turn out. That's good, right? <br /> <br />What should I adjust to smooth out the idle? <br /> <br />I also adjusted the idle stop. It is about a quarter of an inch in, advanced, from what idle stop was on the muffs. That makes it 700 rpm on the water. On the muffs and quarter inch out it was about 900 rpm. I think it's going to be pretty fast on the muffs now. <br /> <br />So I was going to take it for a run. I put it in reverse and it started trying to climb up on the trailer. I lost reverse when I installed my lower unit. :eek: I will drop the lu this weekend and fix that.<br /> <br /><br />The only things I did since last time out was, set/confirm the timing, and make sure there wasn't a kink in the enrichner hose. The latter was most likely the cause from TMD's post. <br /> <br />
TMD <br />I have seen this before....the choke circuit was not working properly.
I will work on the carbs idle mixture. <br />I think it would help, if I were not starting and idling in gear :) seeing how I have the gears messed up.
 

Gold Bear

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Re: Runs on muffs, not on water

isnms<br /><br />"I adjusted the idle mixtures but they are still about 1 1/2 turn out. That's good, right? "<br /><br />Not necessarily. If you have ever dis-connected the fuel line hose (at the end of the day or end of the season) in order to run the carb float bowls dry, you will notice that right before the engine completely runs out of gas, the engine speeds up, then dies. The reason it "speeds up" is because of the lean mixture. When you have the idle mixture screws turned in to 1-1/2 that is a somewhat lean setting, which in turn means you are compensating for that lean mixture setting with a different amount of ignition timing. The ideal idle mixture is a balancing act between the carb idle mixture screws and the single idle speed screw (which initially affects timing more that it affects the carb butterflys). If the idle mixture screws are to adjusted to far in you will have a hesitation or stumble when you try to get up on a plane, and the engine is also harder to start. As many people have pointed out, these engines love a lot of fuel to get them to start. You really do not have to worry about flooding them. The great majority of time starting problems are directly related to not enough fuel ie. lean mixture.<br /><br />I believe your engine will run better when the carb mixture screws are set at 2 turns from lightly seated. If it runs rough look towards problems with the ignition. There is plenty of good advice in this forum about rough idle problems with the I6 engines.<br /><br />PS - I do not recommend running the carbs dry at the end of the day.<br /><br />Good luck,<br /><br />Gold Bear
 

isnms

Seaman
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May 15, 2004
Messages
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Re: Runs on muffs, not on water

Gold Bear - Thank you, that is great information. I have noticed everything you pointed out; engine speeds up when running carbs dry, hesitation when getting up on plane, hard to start.<br /><br />Two turns out it shall be. Then I can back out my idle stop and retard my idle timing.<br /><br />I will also work on my wiring. The ones coming from the distributor are in poor shape. One had the cover split and corrosion inside. I cut out the corroded part and spliced with a butt connector. Another one looks pretty bad at the ring terminal end.
 
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