Idle speed and tach

BRIELLY · #1 07-15-2008, 06:21 PM

Well I finally got the bottom of my engine troubles. Upon rebuilding the carbs I found the bottom one was completely gummed up. I got them back together fired it up and it was idling very high. I turned the speed screw and got it down but now its running rough. I may need to mess with mixture next but the real problem is I have no idea what rpm's its currently idling at. I tried a multimeter with tach attachment but got no reading. I have an older style automotive tach with alligator clips but I have no idea what to hook it up to to get a reading. Can anyone tell me where to connect it? Thanks!

spareparts · #2 07-15-2008, 06:43 PM

I/O OR OB? what kind of motor?

BRIELLY · #3 07-15-2008, 07:17 PM

91 merc

35 ob

spareparts · #4 07-15-2008, 08:26 PM

you're going to have to back that thing in the water to get the idle right, the back pressure of being in the water makes a major difference in the way it idles

BRIELLY · #5 07-15-2008, 08:43 PM

I have it in a a very large garbage can filled with water. Would that be enough?

spareparts · #6 07-16-2008, 09:33 AM

it needs to be pretty high, it should simulate teh water level that the boat will be setting in whenits in the water. I would recomend carring it to the ramp(when the ramp isn't busy). You can set all the idle adjustemnts, and then check the adjustemnts after you put it in gear idling. If you can get it to idle in gear(550-700) without the rpm getting too high in nuetral(generally not over 900 rpm) you'll have it right

drbarbara · #7 07-16-2008, 09:52 AM

I have kind of the same problem. I have a "truck" ford 302 engine and I am having trouble adjusting the idling speed. What should be the correct procedure to adjust the idling speed. Should I put the boat in the water, start the engine and adjust it in neutral to idle at around 900 RPM and then try it in gear or should I start by adjusting it in gear and then hope it does not idle to fast in neutral.

BRIELLY · #8 07-16-2008, 12:37 PM

I was able to get the idle adjusted pretty well but I'm still having the same problem that caused me to rebuild the carbs and fuel pump. When i give it gas it pretty much bogs down and want to stall. There seems to be some gas sitting just inside the carbs. Is this normal or is it an indication that the rebuild went wrong.

tsubaki · #9 07-17-2008, 01:50 PM

Don't know nothin about Merc's but I purchased an old 18hp Evinrude, when they rebuilt the carb they left out the washer between the bowl and upper carb.
It would idle fine but try to flood and generally run like crap when trying to run wide open.
Gas sitting in the carbs sounds like bad or incorrect float setup or something drawing or letting the gas in.
FERM where you at??

Aaww hell.
He's still on that roadtrip to Indiana.

macojoe · #10 07-17-2008, 05:59 PM

I had the same problem years ago, it would bog down the take off, and the plugs would foul out. It was the points.