MerCruiser 3.7 Starting issues

[DoingTheBestICan]

Hello, I have a MerCruiser 3.7 165 HP serial number is B785307.

I have replaced several parts. Here is what’s been done. new spark plugs and wires, distributor cap, rotor, new fuel pump, newly rebuilt carburetor. Replaced all fluids. Compression is 95 on all 4 cylinders.

the engine with turn like it’s supped to, but won’t actually crank. Not getting any spark when I used a spark tester. I set the point gap to what is specified in the manual. The engine will still not fire. Not sure where to turn to next? Could it be the coil or condenser? Can someone point me in the right direction to get this engine started?

thank you

 

[Bt Doctur]

Check for voltage at the + side of the coil
Do you know how to adjust the points? Set points rubbing block on a high lobe, adjust gap to ,018

 

[DoingTheBestICan]

Check for voltage at the + side of the coil
Do you know how to adjust the points? Set points rubbing block on a high lobe, adjust gap to ,018

I did test the coil and I got a negative number -10. something. When I tested the coil not connected to the engine it seemed fine though.

im not 100% on how to set the point. I’ve got the service manual and I will read up on that but if you have any advice that would be great.

 

[Bt Doctur]

key on, voltmeter red to + coil, black lead to a good ground .should see a bit less than actual battery reading

 

[DoingTheBestICan]

key on, voltmeter red to + coil, black lead to a good ground .should see a bit less than actual battery reading

if I’m not mistaken that’s the way I was testing. I will double check today.

 

[Bt Doctur]

https://www.glenngoodspeed.com/volvo/POINTS.HTM

 

[Scott Danforth]

First,

go back to the ignition and service the points

that means file them, gap them, verify the dwell, then set timing

see links 18, and 19. you dont have spark because you didnt properly service the points.

https://forums.iboats.com/forum/eng...ion-for-diyers-an-work-safe-search-version-of

Next, at 95 psi, the motor is in need of a rebuild. even if it runs, it wont have any power. a good motor will have compression of 150 psi in each cylinder.

so you have a choice, you can bore and sleeve you block, or you can find a replacement or you can swap to a V6

 

[DoingTheBestICan]

Thanks for the info and help. I will start working on these today.

 

[kenny nunez]

Just for kicks take a jumper wire from the + battery connection to the + on the coil, then try to start the engine. If it starts then the problem may be the “bypass” circuit. On the solenoid under the manifold the small stud “I” terminal should have 12 volts when the engine is in cranking mode. This is the way the “bypass “ circuit is powered.

 

[DoingTheBestICan]

I replaced the coil and condenser today. I now have good voltage at the coil. I also used a test light on the negative of the coil and ground of the engine and the light lit up while cranking the engine. Am I correct to say I am now getting spark at the coil? I removed the tach wire from the coil and tried to fire the engine up. No luck again. What should I do or test next ?