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1979 mercury v150 starting issues. please help!!!

C

clrkaw

Member
My dad gave me his old boat for Christmas and it was a complete turd, being its sentimental I am completely rebuilding it and almost done. It has a 1979 mercury v150 on it, here is the details. I have to spray fuel in the plugs to get it to fire up, once started it runs like a champ and for about 15 minutes after you kill it you can just bump the key and it fires up, wait about 30 minutes and back to not starting, obviously I'm getting fire and I took the carbs apart myself and They are squeaky clean, my choke butterflies close completely, bowls are full, getting fire. It seems like its just not pulling fuel to the cylinders when trying to start, compression is 90 on all cylinders. It seems like it could possibly be a vaccuum issue or possibly a fuel air mixture issue but runs perfect once started, any and all help is greatly appreciated.
 
My boat does not have a enrichner valve, I have a solenoid that look similar to that but it just closes my choke butterflies, They close completely while holding the key in. Thanks though.
 
90 PSI is not great but workable. What do the plugs look like; brown, black or what? A SN will help. Does the fuel manual primer bulb get firm when squeezed? You spraying fuel into the cylinders indicates an initial fuel delivery issue.
 
My plugs are brand new, there isn't a gap setting because They are just flat without a prong, never seen that before, it does not have any idle issues, it actually runs perfect once running. Could it be a weak battery? It seems to turn over fast at first but will drain a fully charged battery within 15-20 seconds of trying to start, I have two older maxx batts with 675 cca each and have even tried with my perko switch running both and it still drains them in about 15 seconds. Maybe not enough amps?
 
A proper test for spark uses an adjustable tool, not a sparkplug !-------You set the gap to 7/16 and see hiow strong a spark you have.-------Take the starter apart for inspection.-Sounds to me that the starter is the issue.
 
The bulb does get hard, but it feels like air is trapped in it, I ordered a new one 2 days ago, but if it does have fuel in the bowls wouldn't it start anyways? I pulled the bowl screws and They all were full of fuel.
 
Ok, I thought you meant the spark plug gaps, I will try everything suggested as soon as I get home, thanks to all suggestions.
 
I believe the plug wires are about a year old, the only reason I am more on the side of it being a fuel delivery issue other than fire is because after its warmed up it will fire up with a bump of the key with no hesitation but after about 30 minutes when all of it has cooled off it won't start again, but I am going to try every suggestion, I'm bound to hit the culprit somewhere along the way, I was wondering if it could possibly have anything to do with the small tubes that run from the side of each cylinder to the manifold, I'm assuming They have something to do with vaccuum or possibly just air intake. Not really sure though.
 
Agreed you are not " really sure "----These small hoses are part of the oil / fuel recirculation system.--They are not a " vacuum system " either.----Nave little if anything to do with motor starting.
 
Ok, thanks for eliminating that thought. While I have someone with lots of knowledge about this motor maybe you can answer this, the fuel line from the tank goes into a box that then distributes the three carbs lines, there is not a wire or any kind of mechanical part from the motor that connects, just a bolt on part, I have read that its the fuel pump and it would make since but does not look like it could pump in any way and do not see a fuel pump of anyway, I disconnected my fuel lines from the carbs and squeezed the primer and it shot fuel out like a water hose with no resistance, any thoughts or advise on that?
 
The fuel pump on your motor is operated by negative and positive air pulses from the crancase.----A concept that works very well.----There are no wires needed to operate the pump , none at all.----When you operate the manual pump on the hose the fuel is pumped right through the motor fuel pump with no resistance.----You might want to make a small investment in a repair manual for your motor.--It would be money well spent.
 
Might as well at that price, thanks so much for your help. I'm taking the starter off now, just ordered the check valve kit, ordered a new fuel line and primer bulb, picking up a bigger new battery tomorrow and doing a spark gap test tomorrow, I will deffinately let you know all the results. I have built many car engines and race motors for my bikes, two strokes and 4,strokes but this outboard is much different and whipping my butt.
 
The old V-6 with choke butterflys are a bear to start. 1st you have to have a good starter to get airflow pumping thru block. 2nd the butterflys must stay closed when cranking, a weak starter will draw all the voltage so that the choke flaps wont stay shut during cranking. 3rd is compression is low so will make it that much harder to crank. A old trick for these motors and inlines is to install a kill switch and activate it during cranking/choking. This allows a partial flood of carbs, reactivate and start as usually and they fire up in a few seconds.
 
I would deffinately be interested in a electric primer, an enricher valve or whatever it takes. I put a new battery on this morning and still no start, my starter will spin quickly for a few seconds but does seem to be draining battery quickly, I'm about to go through it in a few minutes.
 
Post # 7 recommends that you take the starter apart.-----------Facts are 1--These starters are easy to burn up.---2-- These starters will crank but not fast enough.--3 they are easy to inspect / repair.---------If the armature is fried you may be able to find a replacement armature.
 
Ok, my brushes look perfect but the sides of the magnet is completely smooth because the grooves are so full of corosion, I'm going to clean out the wraps and wire wheel all the corosion off and hope that help.
 
I cleaned the starter out and wirewheeled it, clea ned all connections, put it together and low and behold, she fired up, thanks to everybody, a dirty starter probably would have cost me 5 hrs at the shop. There are some pretty Sharp mechanics on this site.
 
All the cables are new, I replaced every wire in the boat, its pretty fried inside th starter, it worked great a few times after I cleaned it but its 36 yrs old and a bit worn out, I found some on eBay for around 60 for aftermarket and 175.00 for oem but I'm not too sure if the aftermarket is going to spin as fast or the durability.
 
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