1979 or 1980 Merc 70 hp fuel pump?

Hello to all, First off let me say these forums have been a life saver for my family and I, We are fairly new to boating , and recently moved to sunny SW Florida after my last deployment to Afghanistan. While deployed the MRS. decided to take on a little project so that we could take our little Towelbans! out and enjoy the GULF!!. Long story short, New decking, Stringers and a little rehab and I was welcomed home to a sweet little Open bow! so now the dilemma. It has been almost imposible to get this puppy started. I have replaced everything from the tank, new fuel lines, Plugs wires, new prop, fresh impeller, and certinly new gear oil. After my son and I spent an entire day swapping everything out we were all ready to go and she just wont start. I am unsure of the year of the motor but looking at the inspection plate and using the handy dandy search bar up top weve determenid that she is either a 79 or 80 70hp merc, with power trim. I have read countless threads from everyone on here trying to help figure out what ever i can try and I believe my research has led me to a fuel pump. so I removed the ol gas sucker and this is what I have found. Please understand that I have been a grunt on the ground for the past 11 years and now spend my days full time finishing up Nursing school, Besides growing up with dads 14' tiller sea arc my boat knowledge is very slim. I have a pretty good knowledge about 2-stroke dirt bike engines and four wheelers but this seems to be a whole new world. I am ready to order the service and repair manual as research on Iboats has led me to believe it is vital. The few questions I have are as follows:
How can i determine if this pump is bad? are there any hidden fuel system parts I am missing that do need replacing ? This is my first post here on Iboats so I am sorry if I havent explained my self but I am willing to post any pictures or videos I need to get this fixed. SW florida is beautifull and we cant wait to get on the water. (even if we have to use the trolling motor) Thank you to anyone in advance that can help.

Very respectfully,
Tony

Re: 1979 or 1980 Merc 70 hp fuel pump?

your diaphragm is shot and needs replacing, as well as the gaskets. There should also be 2 check valves in the pump. You can tell when the diaphragm is worn out when it is all wrinkled like yours is. That is normal and happens over time. A new diaphragm can make worlds of difference. My advice: Go to your local merc dealer, give them your serial number and tell them you want a fuel pump rebuild kit for your motor. They can look it all up and get you the right parts. I think my kit was 6 dollars. No big deal. Then go get a gallon of Chem-Dip from your local auto store. About 20 bucks. take all plastic off the pump and unscrew the fittings that can be removed. Should be two fittings and one screw. put the pump and the hose fittings in the chem dip for a few hours, then rinse them out with water and let them dry. Then reassemble using the new parts, and back on the motor. This is the process I just completed on my 79 merc 40, and along with the carb rebuild, my motor is running like it's brand new. You may also want to do a carb rebuild. If you decide to do this, do the same thing with the carb. take it completely apart, and soak it in the chem dip. Take all plastic off the carbs before you soak them. and make sure you count how many turns are on your idle adjustment screws when you take them out. A new needle and seat and new floats as well as clean jets can make significantly improve how your motor runs.

Re: 1979 or 1980 Merc 70 hp fuel pump?

Mac, I went this afternoon and ordered the kit for 4 bucks , I will go ahead and do the same for the carbs, parts should be in on Thursday according to the guys at west marine, ill go ahead and remove the carbs tonight and see what i can find Thank you so much for the help

Re: 1979 or 1980 Merc 70 hp fuel pump?

Ok guru's Fuel pump rebuilt, carbs cleaned and rebuilt, still cant get the ol'girl running. After an afternoon of cursing the mercury gods, I checked spark on all cylinders. 2 out of 3 were getting bright blue spark. The bottom cylinder im guessing #3 was the culprit. I removed what I believe is the coil packs (stack of 3) ran down the the marine supply and luckily the mechanic had one laying around. So I replaced the top coil hooked everything back up, and I still have nothing. So I am now completely lost, and still on land! Im really thinking this is an electrical problem but why wont she start with 2 plugs getting spark? I have tried to take pictures of everything I think is important and hopefully the awesomeness of Iboats forum can help me out. Like I said before I am by no means an outboard mechanic but I am pretty mechanically inclined. I also noticed, and y'all can see in the photos there is a wire that looks as though it is not connected and from forum research I located a wiring diagram, and I think it goes to the trigger. I am not sure why this isnt hooked up, Is it needed? My wife called the PO and asked if he had these problems, and he never called back so here we are now, and hopefully we can get this fixed. Thank you for any help you guys can.
Respectfully,
Tony

Re: 1979 or 1980 Merc 70 hp fuel pump?

Here is the diagram I was referring to.

Re: 1979 or 1980 Merc 70 hp fuel pump?

The wiring diagram is correct. That top left-most wire shoud have 'Bias' or 'Wt' imprinted below the terminal, this is no longer used on your model and should not connect to anything.

Download the free Ignition Troubleshooting Guide from the Support page at CDIElectronics.com

Follow the detailed directions to troubleshoot your 'no spark' on one cyl.

It could be a bad plug wire, bad coil, poor coil ground, bad trigger, or bad switchbox. Clean ALL connections.

Check here and see if the factory service manual is still available for free download,

http://forums.iboats.com/showthread.php?t=309079

You will neede a decompression utility like WinRAR and remember the passwprd 'ribforum'