does anyone actually have spark on a 3.7?

[ecupir8]

I have a 3.7 Mercruiser I/O, it has been sitting up for 5 years, and it would not run when it was put up. I can not get spark, from what I have researched the problem of no spark is very common on the 3.7, and from want I gather it always seems to be something different.

I have already...
change the oil
got the motor turning freely by oiling the cylinders, and removed the valve cover to oil the valves, cam, lifters and etc.
installed a new marine battery
turned the motor over a few times to blow the oil out of the cylinders without the plugs in
unhooked the gas tank from the fuel pump (it is full of old fuel)

as far as ignition goes I...
ran jumper wire from the battery,
tested the coil,
inspected the rotor, points, cap and plugs,
inspected all fuses and wires

now, im going to...
replace the condenser (i read of them going out multiple times on some people)
remove or disable the neutal what ever start switch (temporarily)
check the actual ignition switch(i *think* the purple wire on the coil runs to the ignition switch for keyed power)

then if none of this works,
replace the points, rotor and cap

and when ever i get spark, im going to check/adjust the timing, address the fuel problems and adjust the carb, then move on to the cooling system, and lastly the hydraulics.

any other suggestions, especially with the no spark issue?

 

[Don S]

Re: does anyone actually have spark on a 3.7?

Every 3.7 that runs has spark. NO spark usually means the points need replace. Besides that, a full tuneup on a boat should be done every spring for commisioning. Turn the ignition to run, and check the voltage at the coil + terminal. If you have 8+ volts you are fine.
Do a full tune up points, condenser, cap, rotor and plugs. (include setting the dwell, reset timing, and check advance timing)
Hook up to a remote fuel tank with fresh gas and start it up.

 

[ecupir8]

Re: does anyone actually have spark on a 3.7?

Every 3.7 that runs has spark. NO spark usually means the points need replace. Besides that, a full tuneup on a boat should be done every spring for commisioning. Turn the ignition to run, and check the voltage at the coil + terminal. If you have 8+ volts you are fine.
Do a full tune up points, condenser, cap, rotor and plugs. (include setting the dwell, reset timing, and check advance timing)
Hook up to a remote fuel tank with fresh gas and start it up.

the no spark thing was sarcasm.
it just seems odd to me how often I read or hear of a 3.7 without spark, is there a higher quality ignition system for these motors out there?
I guess for now I am going to finish a full tuneup with the standard replacement parts. I am going to start with the condenser and go from there.

and a question, are these motors ford or gm based?

 

[Don S]

Re: does anyone actually have spark on a 3.7?

You don't start by replacing a condenser. You start by doing the points, and condenser. as a set. The most common problem with points in boats is they corrode and glaze over and cause high resistance.
It's not a GM or Ford based engine. It's a failed attempt by Mercruiser to build their own engine. It's an alum. block with a Ford 460 head, Delco ignition system, a rotor/stator charging system similar to that used on outboards.

 

[ecupir8]

Re: does anyone actually have spark on a 3.7?

well i got it running tonight, it ran really good too, i ran it and started it a few times for a while, then i couldnt start it anymore, sounded like an ignition problem (duh).

anyway, i cleaned off the points(it was corroded shut) , and changed the spark plugs, sprayed some ether, and ran the fuel line into a small gas can with some new fuel.
i am going to order all the tuneup parts on thursday, then im going to move on to the cooling system.

where is the best place for mercruiser parts? i have looked at mercruiserparts.com, they seem a little high.

also, a lot of rust and dust was comming out of the alternator at the front of the motor, are there any good ways to clean it out or is it toast?

 

[roadrash]

Re: does anyone actually have spark on a 3.7?

your probally looking at a stator not a alternater. If its bottom dead center= stater. the conversion kit alternater I believe is top left+belt. I would get the boat started first and c if u have to deal with it further. if ya got a alternater conversion kit, your already one up in my book

 

[ecupir8]

Re: does anyone actually have spark on a 3.7?

yeah its the stator, I didn't know the proper name.

I did not know there was an alternator conversion, this is exactly what I would like to do.