1971 Mercury 20hp 200 series will not...

Author Message   Troy Littell New member Username: biggamefisherman Post Number: 1 Registered: 05-2008 Posted on Wednesday, May 14, 2008 - 03:17 pm:    This motor was running fine I was going down the water at full speed an it just started acting like it fouled a plug. I changed the plugs an it still sputters an back fires in the carb. I checked to see if it was getting spark an it was. I guess I need to know if its a carb problem or its not getting enough fire. Thanks Troy   JB Advanced Member Username: beckerjs Post Number: 966 Registered: 11-2005 Posted on Wednesday, May 14, 2008 - 03:21 pm:    coughing and sneezing indicate a lean condition, fuel problem. could be anything from fuel pump, lines, tank pick-up, or plugged tank vent, but more than likely trash in the carb. remove and clean carb, or if you get it running pump the fuel bulb to see if it helps. They all sound good in the driveway   Troy Littell New member Username: biggamefisherman Post Number: 2 Registered: 05-2008 Posted on Wednesday, May 14, 2008 - 03:50 pm:    See I was told that these motors don't have a fuel pump. Could it be I mixed the fuel a little to rich with oil this time on accedent. I'm not talking really really rich but just a little so it smokes. One of the plug wires doesn't snap into the coil like the other one so its a little loose could the be a problem? Thanks Troy   JB Advanced Member Username: beckerjs Post Number: 969 Registered: 11-2005 Posted on Wednesday, May 14, 2008 - 04:04 pm:    no and no. On break in of a rebuilt or new engine you run double oil, with no ill effects, maybe a fouled plug once in a while. The coil wire will only effect that one cyl, and won't back fire or cough through the carb. You could bend the tab on the coil wire to make it fit better. If you want to check for spark then hook a timing light up to the plug wires while running. All engine need some type of pump unless the tank is gravity feed, higher then the engine.   JB Advanced Member Username: beckerjs Post Number: 970 Registered: 11-2005 Posted on Wednesday, May 14, 2008 - 04:09 pm:    one more thing can cause the spitting through the carb, bad reeds or debris in the reeds. not uncommon but requires engine tear down for replacement   JB Advanced Member Username: beckerjs Post Number: 971 Registered: 11-2005 Posted on Wednesday, May 14, 2008 - 04:31 pm:    http://www.usboatsupply.com/Mercury_Mercruiser_Parts_Catalog3a.php?mc=01&ms=2050 &si=447 fuel pump   Robert New member Username: starville Post Number: 1 Registered: 05-2008 Posted on Friday, May 16, 2008 - 10:37 am:    1976 Mercury 20 hp. serial#4410261 Starts and idles perfectly, accelerates like a rocket, goes like a bullet for about 2 minutes or maybe a mile. Tried swapping fuel line, tank, then I soaked, blew out and rebuilt the B-Series MerCarb and its integral fuel pump. Later, I took out fuel strainer, found and replaced leaking crankcase bleed line, tried all combinations of pump check valves in carb kit. Was not happy to see new style hollow plastic float with no drop adj.(motor had foam float with brass height and drop tangs) , but put it in anyway, and then again at higher end of spec (higher bowl level, which did prolong good running time) as described by insert sheet in float package. Does not flood. Starts instantly in Michigan 40° water. Does not miss or falter one single bit upon acceleration from idle, in gear. Idles at dead slow indefinitely. Boat will plane at half-throttle and will run a long time that way. Will run forever at full throttle as long as I give primer bulb a squeeze every half-minute or so. While faltering, engine will recover immediately when bulb is squeezed. New tank, new fittings, removed tank vent, 2 new bulbs (last one Merc branded), new Merc silver hose, all steel screw-type hose clamps. Also probed crankcase pulse hole with soft tool and shot aerosol throttle body cleaner through it. New carb base gasket. New plugs, L78V. New inlet strainer, cap and gasket. New fuel crossover hose and clamps (was leaking air, but this did not correct surging). New female fitting on new fuel line, fits snug on engine fitting. Engine fitting smooth and clean, no burrs, bayonet pins not worn. No debris found inside fitting. Are there any other possible pump faults? Is it possible to run the bowl out of gas if the motor is over revving, such as with the wrong prop? Or should the pump be sufficient up to extreme RPM's? I will tach it today anyway. emails welcome, no spam, change ".nut" to ".net" piratebob@webtv.nut   JB Advanced Member Username: beckerjs Post Number: 980 Registered: 11-2005 Posted on Friday, May 16, 2008 - 11:08 am:    check compression   'Bandit Advanced Member Username: timebandit Post Number: 337 Registered: 09-2007 Posted on Friday, May 16, 2008 - 05:46 pm:    What I would do here is remove all the screens and carb filters from the system and try that. Anti-syphon valves also should be removed.   Robert New member Username: starville Post Number: 2 Registered: 05-2008 Posted on Friday, May 16, 2008 - 06:06 pm:    Yes, I did that. No screen in pickup pipe of brand new tank, new Quicksilver primer bulb and line, cut the side out of fuel screen at pump, changed float, new diaphragms and check reeds in pump with new gaskets. Found other leaks and corrected them. I put the boat against a tree and ran it WOT for 15 minutes with no problem, but when it runs free on the river, it only lasts for 1 or 2 minutes before fading. Will run 3/4 thrttle no problem. Squeeze the bulb every 15-30 sec and it will run forever at WOT. I sent prop in for new hub and recondidioning today, thinking it may have been over-revving, but I really doubtit because that was the highest pitch prop available for that engie that year.   'Bandit Advanced Member Username: timebandit Post Number: 338 Registered: 09-2007 Posted on Friday, May 16, 2008 - 06:30 pm:    Would it be possible to enlarge the inlet seat a few thousanth's without messing it up? Some of these era motors had known problems that required a rework of some sort to the carb. This could be the bowl air vent as well.   problem Visitor Posted on Thursday, June 26, 2008 - 11:58 am:    mid 70s merc 20hp sometimes only runs with choke other times no choke but dont idle. carb was rebuilt last yr. has a mind of its own, whats going on

Administration Log Out   Previous Page Next Page

Home / Directory | Engine Manuals | Engine Parts | Discussion Board | Free Classifieds | Orders / Shipping | Contact Us | View Cart

About Us | Terms of Use | Privacy Policy MarineEngine.com, 184 Jones Dr., Brandon, VT 05733 USA Phone: 802-247-4700 FAX: 802-301-1034 info@marineengine.com Copyright © 2000 - 2007 by MarineEngine.com, Inc. All rights reserved

Traduca Traduisez Traduza Traduca Ubersetzen