mercruiser 3.0 1987 not starting

Mattdade · Sep 8, 2011

I have an 87 3.0 that wont start. at first the spark seemed too weak.I think I have that fixed.It doesn't seem to be getting any gas to the cylinders.I rebuilt the carb and the gas is flowing like it should.there doesn't seem to be very much suction at the intake. checked the compression and got 110 in the first three cylinders and 90 in #4.could a valve be sticking open? keep checking plugs never see any gas or anything on them they are new. any help would be great!

86 century · Sep 8, 2011

Re: mercruiser 3.0 1987 not starting

The compretion is high enough to run. If you have fuel and spark the only thing left is timeing.
Is the fuel good.

Mattdade · Sep 8, 2011

Re: mercruiser 3.0 1987 not starting

I put fresh gas in this morning,also changed the points and condensor.the boat had been sitting for 5 years before I purchased it this week .the spark may still be too weak.I also put a new coil on it today.

jimbo_jwc · Sep 8, 2011

Re: mercruiser 3.0 1987 not starting

My 1987 3.0l 130 HP Mercruiser had 30 hrs on when I bought . Points need filed cleaned and set , new plugs ,Fuel pump rebuild ,Carb rebuilt , Choke fuse holder fixed , Antisiphon valve cleaned, Lower unit pulled and universals greased and it runs like new and oil and filter original . Thermostat and oil change nextyear .
Love my I/O . Have ran about 10hrs and dumped 5gal of gas and bought $18.76 worth of gas . Mounted 4.5hp Johnson Seahorse Twin as kicker /trolling motor and I am im heaven w/Boat. Always Tested in Drum with hose on and drum on kicker filled plumbed to lower with vacuume cleaner hose to Lower unit Mercruiser lost pump impeller first it was able to WOT to 5000 rpm .

Pikey23 · Sep 8, 2011

Re: mercruiser 3.0 1987 not starting

jimbo, isn't 5000 rpm a little high for that motor? my 1985 merc 3.0 is only rated to run 4200 to 4600 max

glennj3 · Sep 8, 2011

Re: mercruiser 3.0 1987 not starting

Mattdale, first make sure you do have spark at the points with the keys on. Of course if you have plugs firing then skip that part. Then with the engine turning over, put your hand over the carb (to create more suction than the choke does). Look inside to make sure you got gass in there. If so, you should be getting gas into the plugs although it could be flooded.
When Mine sat up all winter it would not crank. Did this did that just would not crank up. I must have flooded it, after sitting several hours she fired right up. Pushed the throttle full forward, then back about 1/4 open, water on the intake and turned her over. She always runs rough for about a 1/2 minute then smooths out. Starting fluid would not even help start her.

Mattdade · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Thanks Glenn,I will try your tips..It sounds like what mine is doing.Im still wondering about the weak looking spark .i have 13.5 volts on the pos side of the coil and have changed the points and condensor,spark plugs and coil.the only thing left is the cap and rotor,do you think it will help to change them out?

jimbo_jwc · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Yes but in neutral and after running trimed up this little motor has exceeded max WOT with load running down lake but not for long . I like the feeling I got a little more and can pitch to 19" . Posted a question about overreving and blow ups from this and got no replies so don't know how much of a danger it is ?

Mattdade · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Mine has a 17" pitch but i have not tried it yet because it wont start.hopefully its the right prop.

Pikey23 · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

matt, I am sure you have already done this. But, have you tried starting fluid directly into the carb? I know you said that you rebuilt the carb and have fuel, but is it enough fuel? Another thought that is kinda out there, My manifold had a small crack and I had a small amount of water getting sucked into the cylinders on the intake stroke. The plugs where getting wet and not firing. Just a thought.

Mattdade · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Well I got it to start finally the dist was 180 degrees off .previous owner took it out didnt put it back right.it is idleing rough.cant get to the idle screws they still have caps on them.should I drill them out?Had to change the water pump impellar in the foot.can anyone tell me where and how much oil to add in the drive unit. Thanks

jimbo_jwc · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Used gear oil container full of gas with hose to prim the found out you can pour gas thru carb to fill float boal area and would run after opening points . Choke was way off fixed and rebuilt carb and fuel pump only to find out antisiphon valve not opening enough ,after cleaning every thing run right , used half of starters life but am now sure of engine .

jimbo_jwc · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Mine has mercruiser carb , one idle screw , Changed Impeller by leaving in fwd gear unbolting removing lower half ,screw under allen removable anode for hidden bolt , bought 2 qts and pump to fill after done still have alot left from second qt when comes out top plug .

Pikey23 · Sep 9, 2011

Re: mercruiser 3.0 1987 not starting

Mattdade said:
Well I got it to start finally the dist was 180 degrees off .previous owner took it out didnt put it back right.it is idleing rough.cant get to the idle screws they still have caps on them.should I drill them out?Had to change the water pump impellar in the foot.can anyone tell me where and how much oil to add in the drive unit. Thanks

The drive takes a little more then one quart. Take the bottom plug out of the lower unit and the top vent plug out of the upper. Pump the oil in from the bottom until it comes out of the top vent hole. Do not put it in from the top. Make sure the drive is trimmed all the way down. My merc 2 barrel carb only has one idle adjustment screw also.

Mattdade · Sep 10, 2011

Re: mercruiser 3.0 1987 not starting

My problems are over for now,I hope.I changed the impeller and the starter solenoid and she fired right up!I timed it and it runs so smooth I couldn't believe it.Not too bad for an 87 that sat up for 5 or 6 years.I spotted a crack on the shifter bellows ,I guess that's my next project.and the carb only has one idle screw.DUH!Thanks for the support from everyone.maybe I will get to use it for the last couple of weeks of scallop season after all!!

mercruiser 3.0 1987 not starting

Cadet

Ensign

Cadet

Ship Happens

Petty Officer 3rd Class

Petty Officer 1st Class

Cadet

Ship Happens

Cadet

Petty Officer 3rd Class

Cadet

Ship Happens

Ship Happens

Petty Officer 3rd Class

Cadet