3.7 merc no spark

[Bobl]

I just got a 1901 starcraft with a 3.7 mercruser. I was told it runs good but not started this season. It cranks great but I get no spark. I did minor test check spark at plugs and from coil but none. checked firing order. I replace the coil and the condensor. The points look in very good shape and I have them gapped to the specs or at least very close. Fuel is not a problem. I am limited as to testing tools and woking on these motors. The saftey neutral switch or gear switch is bypased right now to get that out of the loop for now. I am praying for something I have over looked.
Bob

 

[Fishermark]

Re: 3.7 merc no spark

Hi and welcome aboard!

My first guess would be the points. You say they look good, but the chances are good that they are glazed. They need to be replaced, or at the very least lightly sanded and cleaned.

 

[Bobl]

Re: 3.7 merc no spark

i will try it. I lightly sanded them some. I did very little but didnt want to damage them. I called for parts yesterday and all anyone told me is that I will have to pay big $$ to have an upgrade done

 

[Bt Doctur]

Re: 3.7 merc no spark

Keep the points,forget the upgrade ($$$$$$$$$$$$$$$$$$$$$)
for $6.00 for points you cant go wrong

 

[Bobl]

Re: 3.7 merc no spark

well itried local auto stores with limited boat stock and no lck I will swing by in the am and get points. I did clean these up again and got nothing. What is the chance it might be a bigger problem.

Also you guys are great I was reading through alot of the other post and found many helpfull hits and fixes!!

 

[searay3]

Re: 3.7 merc no spark

Check for voltage at the plus side of the coil. Thats the opposite side that the wire is for the points. If you do have voltage, disconnect the tach. If not, trace back from the pos side of the coil. Couple of things to try.

 

[Bobl]

Re: 3.7 merc no spark

ok it is a great day! I started over and traced my steps and after finding power to the coil and power when cranking I put the old coil in and it sputtered. I was given the wrong part. I adjusted the poins again to be sure and it fired right up. Charging and all. Now I will change all the fluids. and get to the lake. Thank you all!!

 

[searay3]

Re: 3.7 merc no spark

Great things are working again. Basic maintenance. Replace those points and run thru a full tuneup. Cheap insurance for a trouble free season. Do it again in the spring. Boat motors are hard working engines. Cap, rotor, points, using a dwell meter, plugs and carb adjustments. Don't forget the filters. Fuel, water seperator, if you have one, clean the flame arrestor. Costs a little cash, priceless for frustration.

 

[ne7800]

Re: 3.7 merc no spark

i have a 1980 four winns with a 470 (3.7) just a little tip when looking for eletrical parts the cap and rotor points and condencer come from a 1964 chevy 4 cyl at least they did in 1980