Starting Mercruiser on Engine Stand **UPDATE**

[Alpheus]

I have rebuilt a Mercruiser engine and I'm trying to get her to fire up. I have tried just adding some jumper wires to the harness instead of using alligator clips to the coil, but I cant get any spark. I just need another set of eyes to confirm if what I'm doing is right.

I put a jumper wire between socket # 1 & #2 for the ground and #5 & #6 for the hot. I have the battery(+) running in to the starter and grounded to the block. I have a remote start switch connected between hot and pin # 7 to activate starter. Am I missing something?

This is a 91 Mercruiser 5.7 and the pic is from the manual on page #396.


Any help would be greatly appreciated. Thanks...

.

 

[Don S]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

Put the jumper wire from the battery positive cable to the coil + terminal. Then crank it over with your remote starter. Should have spark. To shut it off, remove the jumper.

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

Something is wrong. I noticed that the coil is getting extremely hot. I disconnected the battery and started to look for a short. Ohms across the coil = .95, ohms from pin 5 to pin 6 = no continuity (OL) ohms from pin 1 to pin 2 = 1.3k. When I unplug the ignition module from the distributor it = (OL).
Looks like the ground wires are bleeding together in the ignition module. I don't have a schematic of the ignition module itself. Is there a fault isolation manual for the ignition module?

 

[Fun Times]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

I put a jumper wire between socket # 1 & #2 If you did this then this is why it is getting hot and not starting. Un hook this wire you do not need it right now.

All you need to do is jump #'s 5 & 6 Then touch # 6 to number 7 till it starts then pull # 7 when started, And to stop engine pull 5 or 6. your done. Because you should have the batt hooked up to the starter and the ground hooked up to the block, If everything eles is hooked up right to your engine harness it should start and run.

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

I nixed the jumpers and just ran wires to the coil from the battery and the coil got very hot and burned the positive wire I had going to the coil off at the terminal when I turned the engine over. This is a strange situation I got going on here.

 

[havasuboatman]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

Are you using an internally or externally resisted coil? Do you have the coil hooked up correctly? Did you buy the replacement coil yet? Do so.

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

Its the stock Mercruiser coil. I ohmed out the coil and its within spec according to the manual...

 

[havasuboatman]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

So, everything is wired correctly, the coil tests good. It just doesn't work, and gets really hot.
Try this:
Disconnect everything from the coil.
hook up your test light or whatever you are using to verify you have spark
Take a jumper wire and hook it from the battery to the coil +
Take another jumper wire and hook it to the coil - DO NOT TOUCH THE OTHER END OF THIS WIRE WITH YOUR HAND!!! but do touch it to a ground on the engine while looking at you spark verifier.
If you dont get a nice bright spark, your coil is junk.
Just be very careful or you will be lit up like a christmas tree. Hurts like a M F

 

[Bondo]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

Just be very careful or you will be lit up like a christmas tree. Hurts like a M F

Ayuh,....

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

So, everything is wired correctly, the coil tests good. It just doesn't work, and gets really hot.
Try this:
Disconnect everything from the coil.
hook up your test light or whatever you are using to verify you have spark
Take a jumper wire and hook it from the battery to the coil +
Take another jumper wire and hook it to the coil - DO NOT TOUCH THE OTHER END OF THIS WIRE WITH YOUR HAND!!! but do touch it to a ground on the engine while looking at you spark verifier.
If you dont get a nice bright spark, your coil is junk.
Just be very careful or you will be lit up like a christmas tree. Hurts like a M F

I will give that a try...

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

I got it running!!!

I thought that a separate ground had to be going to the coil, but I was wrong. It looks like in the schematic that the grey wires for the coil ground were not connected, but they are through the ignition amplifier. Jumper between 5 & 6 and a hot to pin 7 to activate starter was all that it needed. Thanks for all the help...

 

[Bt Doctur]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

The grey wire is main harness is the tach feed ,not a ground.,the grey wire from the amp is the neg side of the coil . No additional grounds required

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

The grey wire is main harness is the tach feed ,not a ground.,the grey wire from the amp is the neg side of the coil . No additional grounds required

Gotcha. Thanks allot...

 

[betayv]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

hi there hey if is posible for you to take pics or video of what are you doing I whant to start a marine engine prior to installation for my wellcraft restoration.

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand

Re: Starting Mercruiser on Engine Stand

hi there hey if is posible for you to take pics or video of what are you doing I whant to start a marine engine prior to installation for my wellcraft restoration.

Ya I can do that. Give me a day or two and Ill put one together...

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand **UPDATE**

I ran the engine for a little bit yesterday and made a little video of what I do to start it. This is a crude method of activating the starter so I don't recommend it. I lost my remote starter or I would have used that. You could also use a screwdriver and jump the terminals across the starter, but that marks up the threads on the terminals, so I don't recommend that either. But to each is own...

First is connect a jumper wire from pin #5 to pin #6. I then use a hot wire to insert into pin #7 to activate starter. I used a multimeter to confirm that I had oil pressure buy checking the resistance from the oil sending unit to ground...

You could also run a hot wire directly from a battery to the positive of the coil...

http://www.youtube.com/watch?v=NUoXFIo2Ab8

 

[Don S]

Re: Starting Mercruiser on Engine Stand **UPDATE**

One thing I would suggest, is NOT to use the jumpers like that in the plug. Especially with the starter. If you arc and get buldup or a bump on the plug, you may have problems making a connection with the other half.
Instead, just a jumper lead from the battery positive cable to the + terminal on the coil.
For starting, a jumper on the slave solenoid would be a lot safer.

One other thing I do on engines when started like that is to hook up a mechanical oil pressure gauge so I can see what it's really doing, then compare that info with what the electrical gauge says when I put the engines in a boat. Especially if they are new engines

 

[Alpheus]

Re: Starting Mercruiser on Engine Stand **UPDATE**

One thing I would suggest, is NOT to use the jumpers like that in the plug. Especially with the starter. If you arc and get buldup or a bump on the plug, you may have problems making a connection with the other half.

That's a good point, because I know that the coil uses 14 amps and that could make a good arc. OK so just run a hot lead from battery to + terminal on the coil.

One other thing I do on engines when started like that is to hook up a mechanical oil pressure gauge so I can see what it's really doing, then compare that info with what the electrical gauge says when I put the engines in a boat. Especially if they are new engines

Another good point.
I know the conversion for what ohms = oil psi, but that doesn't mean squat if the sending unit is bad. I will be putting a mechanical gauge on it today...

You learn something new every day...

 

[betayv]

Re: Starting Mercruiser on Engine Stand **UPDATE**

hey man thank you very much for the video and thank you very much to the other on the forum explaining how to do it.

 

[Speakrdude]

Re: Starting Mercruiser on Engine Stand **UPDATE**

Great video. A couple of things though.

If the engine runs rough, like they usually will at first untill you get em dialed in. If the engine is not bolted down, it could fall off those stands. And, if your gonna run for an hour, during the initial break in, you'll want to run the RPM's around 1500 to get a good cam break in. Does this agree with the rebuilding pro's or do you still break in the cam and others this way?

Whenever I try to run like that with the water hose, the raw water pump sucks the hose flat.

I saw a video from Michigan Motors on "You Tube", and they had a big water trough at the end of exhaust tubes that served dual purpose. Not only did it serve as a water supply for the Raw Water Pump to suck from, it provided a place for the exhaust water mix to return so the flooding issue was minimized.

And yes, Oil Ps and temp gauge a must. Also a good time to make sure alternator is working before dropping in and changing out afterwards. Do ask me how I know.