75 mercury wont start

Hey guys i am new to this thread and will be doing a lot more asking than answering. I have a fisher 1610 that i bought brand new in 2006 with a 40 horse mercury upgrade.I sold it a couple years later to a guy that paid half the money down on it. He came to try the boat out one weekend took it out and i did not see him again until about 2 weeks ago.Needles to say after a kind exchange of words i got my boat back ragged out. He had taken the original motor off and put a 75 mercury on that i have no clue about. Anyway i have completely redone the whole boat with new carpet seats etc. The motor looks pretty good but i cant get it to start it turns over good but i cant tell if it is missing fuel or fire i am expecting the worst but hoping for the best. Like i said i am no mechanic just basic knowledge. He has had the boat for about 5 years when i ran into him i should have choked information out of him about the boat but i just got it and came home. So hear i am now begging for someone to point me in the right direction. So thank you in advance for any info.

Re: 75 mercury wont start

Do a compression test and see if you get readings around the 90-140 psi range. All cylinders should be close in range to work properly. Take out your spark plugs and look for corrosion or water damage, replace all plugs anyway. Check the coils by checking for spark on each coil wire. You may need to rebuild the fuel pump, which is just a few springs and gaskets. You may need to take off the carburetor(s) and clean them and/or install new floats/needles. You may need a new stator/trigger or power-pack(s). You may simply need a new fuel hose/squeeze bulb. There are threads you can search here for each of these problems.

Note: Once you are up and running again, it is a good idea to use Seafoam in your gas tank several times a year to keep it clean all up in there! Good luck.