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My 1978 Merc 150 is Hard to start when cold

d4bell

New member
I have a starting problem when cold. I noticed that when I pump up the primer bulb it never get's hard and I can hear gas going threw lower carbs I think. Leaks gas out front of motor by air filter. Do I have a blown seal or something? It has always been hard to start. Have cleaned all starter to Battery connections. Motor turns over fine, with throttle up and choke button pushed it will fire one cylinder and kick out starter. The only way I can get it started is to keep pumping primer. Eventually I can get it started if the battery holds up. any suggestions,Thanx in advance for any help:confused:
 
Sounds like a stuck/clogged/shot float valve (or float).

If (something) won't allow the float valve to close properly and stop the flow of gas, all that pumping effectively floods the carb which in turn can flood which ever cylinders are associated with that particular carb, which would make for a very hard start...
 
thanx for the info. Do I need a carb manifold gasket to remove carbs for cleaning? I would like to clean carbs but want to put them right back on . will order what I need first. What other things or parts will I need?
 
Those motors always started hard. There was an upgrade kit that you had to drill holes in the top of the carbs and add fuel fittings coming from the primer that was included with the kit. Basically it got rid of the chokes shutters and added the fuel primer system instead. I'm not sure if these kits are still available though. I don't have the old books anymore, but maybe some else does.
 
I'm new to the forum and was reading through the old posts and came across this post.I've read a lot of posts on a lot of forums and this is the first I've heard of a primer kit.I would love to see a picture of where the hole was drilled in the carbs as I have been seriously thinking about adding my own manual priming system.Was thinking of using a primer off of a snowmobile engine,but would look into buying the kit if it is still available.
I'm running a 73 150 l6 right now,but have a 150 V6 to install.I wanted to make sure the L6 is working really well before I pull it off of the boat in case I want to sell it later.I have it running pretty well but it is way too hard to start when cold.I'm to the point of spraying fuel/oil mix into the carbs at home on the muffs before I take it to the lake.Even at that I start it on the trailer before launching.Primer would definitely an improvment.
 
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These " fuel primers " were first offered by OMC ( Johnson / Evinrude ) in the early 1980's and later by Mercury.------------Definitely an improvement over choke shutters.------------------So visit a dealer that might have older OMC's in the junk pile and get all the pieces.--------------I have lots of them as well in Southern Ontario.
 
I have installed the OMC electric primer on inline 6 Mercury motors.--------------No more hard to start issues after one of those is in use.
 
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