79 115hp mercury help

[mike10gs]

Hey everyone, so I have a 79 merc, 115hp. It came on boat that I bought. 79, 17ft marlin. I bought this last august. It's my first boat so I don't know much on engines. I used it maybe 5 times in salt water and yes I did run water through it after every use. And used it maybe 4 times in freshwater. It ran great, was strong and was going atleast 26mph.
Winter came so it sat for a while. I did go turn it on a few times, so it wouldn't go all winter without turning on. About 2 weeks ago I was taking the boat out on the lake for a spin. Before doing so, put the muffs on and turned it on to see if it was going to run. It turned on easily , spitting water, warmed it then I put it in gear and was going fine. The prop was spinning. Only thing I've realized when turning it on is when I would put it in neutral it would die. Never did that before. But anyways so I went out thinking everything was good.

Got to the launch, turned it on , everything seemed fine, then I put it in reverse and it turns off. Turn it back on try again and turns off. I try going forward and kept turning off. It would start up on choke but as soon as I out it in gear it would die. I tried leaving it in neutral and turning it on since it had been warmed up but nothing. Kept trying then finally it went in reverse, got out enough to turn around put it in forward died again. Turned it on , kept trying finally it went into gear. As I was going I reach out enough to punch it but it wouldn't give me full power. I was doing maybe 8 mph to 10mph top. I could hear it want to slow down so after about 10 min driving around I went in.

Can someone please help to what this may be? Would like to get into working on engine myself. Please if I could get some help I would appreciate it. Sorry I made it long. Thanks again in advance

Mike

 

[Chris1956]

Mike, your description could be several items that are wrong or some combination of them. Take a compression check. See if she has spark on all cylinders. Do you have a single coil distributor ignition or a 6 coils and no distributor? How old is your fuel? Is it mixed at 50::1?

Post back.

 

[racerone]

Was a new waterpump impeller installed after you bought it ??

 

[jimmbo]

Old, unstablized gas from last year? Sounds like the carbs are gummed up

 

[mike10gs]

Thank you guys for replying. Sorry I'm new so how will I check for spark on all. My fuel has been there for a couple months. Maybe 4 or 5. I've turn her on. I did try adding new gas before I went out but not sure if I mixed correctly with oil...

Yes it is 50:1.. I just now bought a bottle that shows me how much oil for amount of gas. Will be changing gas with new and right amount of oil.

No I have not change anything on it since I've bought it.... what would be some things to change on it since I have not done any work on it and he had it sitting for a bit before I bought it.

Guy who I bought it from said he had it checked. Gave me a paper that showed all compression was good. But then again once he had it checked. He got sick and never got it out and sat for few months before i bought it.

I'm thinking of tune up... lower oil change. What else could be done.? Is there any good videos for a motor around my year? Thanks again for all help. Will be checking her out tkmorrow. Will try and start her up with new gas and oil and go from there.

 

[mike10gs]

One more thing. What is single coil distributor ignition, or 6 coils and no ignition ? Again sorry I'm new to outboards but would like to learn to do my own work. Thanks guys.

 

[Chris1956]

In 1979, Merc switched from distributor/coil ignition to ADI ignition. If you have a distributor cap (usually blue) on the port side of the motor with six yellow spark plug wires, you have battery powered CDI Distributor ignition.

On the other hand, if you see short spark plug wires running to individual coils (six in all), you have Alternator Driven Ignition (ADI).

 

[CharlieB]

The most common cause of dying once shifted into gear is a lean idle mixture caused by dirty carbs. This is caused because boats are not used daily like our cars. The gasoline evaporates from the carbs leaving the oil which tries to dry leaving a gummy residue restricting the very small fuel passages.

Verify spark and compression on each cyl to rule out other possible problems. Once you are sure both of those are fine it is safe to assume your problem is with fuel delivery. Do NOT skip this step as it can come back and haunt you later.

Nothing beats a complete disassembly and cleaning, replacing gaskets, setting correct float height, then proper linkage adjustment and final idle mixture setting once on the water. All of these are well covered in many threads here. Learn to use the 'Search feature, 'carb cleaning' then 'link and sync'. You will find detailed instructions for each.

Installation of a in-line spin-on canister fuel-water separating filter looking like a common oil filter can make sure your clean carbs stay clean preventing any particles or drops of water from getting in there. A very wise investment to keep your motor more reliable. These are available at most boating supply sources, here, also some Wal-Marts. Check prices.