1979 Mercury 40 HP

[TheChad]

Hey All,<br /><br />We just bought a 1978 Rinkerbuilt 15' fiberglass boat w/ 1979 Mercury 40HP Motor..<br /><br />It does start, but only runs for about 30 seconds... The owner said it ran just fine last year. We got the whole boat/motor/trailer for $650.<br /><br />Anyway, right off I have noticed 2 things that may or may not be part of the problem...<br /><br />#1: There are 2 different Spark plugs installed, NGK & Champion. I doubt that would cause too much problem, but to make sure, i have purchase 2 new Champion spark plugs to install.<br /><br />#2: Check out the picture below... The hose that is circled in the picture has has split in 2. I don't know what this hose does, but it i believe fuel has come out this hose.. So weather or not it is the problem, it is definitly A problem..<br /><br />

<br /><br />What is this hose for?<br /><br />I will be attempting to fix this hose tomarrow (08/30/2005). I will post any updates as i work on things..<br /><br />Any suggestions from anyone as to what else i should check?<br /><br />Thanks!<br /><br />-TheChad

 

[stan_deezy]

Re: 1979 Mercury 40 HP

Fuel? Is it the old stuff that came with the boat/engine or have you bought and mixed nice new stuff?<br />Try pumping the primer bulb to keep it running; might be fuel pump.<br /><br />Just a couple of easy hits.....

 

[TheChad]

Re: 1979 Mercury 40 HP

Originally posted by Bro:<br /> Fuel? Is it the old stuff that came with the boat/engine or have you bought and mixed nice new stuff?<br />Try pumping the primer bulb to keep it running; might be fuel pump.<br /><br />Just a couple of easy hits.....

Yeah, the fuel is what came with it, I just got it today, so i havent done anything with the fuel..<br /><br />You are the 3rd person today to suggest it could be a fuel pump.. The battery is charging tonight, tomarrow, I will try the primer bulb...<br /><br />-TheChad

 

[stan_deezy]

Re: 1979 Mercury 40 HP

CHANGE THE FUEL <br /><br />outboard fuel has a life of 90 days approx after that consider it US (as in useless)

 

[stan_deezy]

Re: 1979 Mercury 40 HP

meant to add: you wouldn't believe the number of great outboard engines I have bought for a few pennies and the line is always the same.......<br /><br />"...dunno what's wrong with it, ran great last year but now it cuts out all the time" and it's nearly always "sor fuel" that it is the problem: replace the fuel and away she goes purring like a kitten.

 

[TheChad]

Re: 1979 Mercury 40 HP

Alright, I will definitly change the fuel.<br /><br />Do you, or anyone know what that hose in the picture is?<br /><br />Thanks,<br /><br />-TheChad

 

[joblo33]

Re: 1979 Mercury 40 HP

Looks like the cylinder block to fuel pump hose. If so that's your problem, the fuel pump wont pump correctly until it's replaced. You might be able to replace it with hose from an automotive store instead of buying the part from Merc.<br />Eric

 

[TheChad]

Re: 1979 Mercury 40 HP

Originally posted by Eric B:<br /> Looks like the cylinder block to fuel pump hose. If so that's your problem, the fuel pump wont pump correctly until it's replaced. You might be able to replace it with hose from an automotive store instead of buying the part from Merc.<br />Eric

I hope that's all it is! That would be great.<br /><br />Where might I find the serial Number on this motor?<br /><br />Thanks,<br /><br />-TheChad

 

[joblo33]

Re: 1979 Mercury 40 HP

On the plate between the transom clamps up high, just below the front chrome emlem you take off to remove the cowling.

 

[TheChad]

Re: 1979 Mercury 40 HP

Okay, Here's the update:<br /><br />I replaced the hose that was broken, the Spark Plugs, the fuel line (From the tank to the engine), and the fuel inside the tank.<br /><br />The running problem is still unaffected... It will start, run for about 15 seconds, and die.<br /><br />However, we did some testing... Once started, if we pump the primer bulb, or spray squrts of carb cleaner into the carb, the engine doesn't die...<br /><br />If i am correct, this tells us that the fuel pump has gone bad.. Can anyone confirm this? If not, what else could be the problem?<br /><br />Thanks for the help,<br /><br />-TheChad

 

[joblo33]

Re: 1979 Mercury 40 HP

Sounds like the fuel pump. Get a fuel pump kit, clean out the pump, and replace the gaskets and diaphragms with those from the kit.<br />Eric

 

[stan_deezy]

Re: 1979 Mercury 40 HP

Sounds like fuel pump.

 

[TheChad]

Re: 1979 Mercury 40 HP

Since I don't know the history of this engine, is there any other parts i should service/replace?<br /><br />The engine spits plenty of water, so i can assume the water pump system is working good.<br /><br />Should I take the engine in and have a checkup service performed? Or if it runs good after replacing the fuel pump, is it safe to assume the engine is in good working condition?<br /><br />Thanks for the help,<br /><br />-TheChad

 

[andy6374]

Re: 1979 Mercury 40 HP

If it ain' broke, don't fix it. If it has compression, fuel, and spark you are good to go. My biggest concern with buying an engine of which I know nothing about is making sure the water pump is good. If it has a good stream out the tell tale, you're fine.<br /><br />Just my opinion-<br />andy

 

[TheChad]

Re: 1979 Mercury 40 HP

Originally posted by andy6374:<br /> If it ain' broke, don't fix it. If it has compression, fuel, and spark you are good to go. My biggest concern with buying an engine of which I know nothing about is making sure the water pump is good. If it has a good stream out the tell tale, you're fine.<br /><br />Just my opinion-<br />andy

Is there a way to test compression with out buying a compression tester/gauge?<br /><br />I know of the Compression tester/gauge, but have never used one, I assume you just screw it into the spark plug hole, and turn the flywheel?<br /><br />I've worked on many 2-stroke engines before, but none bigger than 400cc, and none were marine engines, so I'm still learning about thease..<br /><br />Thanks for the help,<br /><br />-TheChad

 

[stan_deezy]

Re: 1979 Mercury 40 HP

I'd change the gear oil out too but apart from that I wouldn't do much else: I agree that "if ain't broke it soon will be" is a good saying <br /><br />let us know how you get on with the fuel pump.

 

[stan_deezy]

Re: 1979 Mercury 40 HP

meant to say: if it's running then don't bother looking at the compressions unless you are really keen or looking for a fault. I only look at them when I first get an engine as it means I have an easy "check-back" to see if there has been a change when something does go wrong. Compression testers are cheap and I use an automotive one picked up for a few pounds (approx $10) in a local motor factors.

 

[Nos4r2]

Re: 1979 Mercury 40 HP

If it's been stood up for a year I'd change the impeller as a matter of course. It isn't expensive and it could save your engine.<br /><br />You never know when it was last changed or how perished it is.

 

[TheChad]

Re: 1979 Mercury 40 HP

Well, I am having a hell of a time just checking to see if the local dealer can even order the fuel pump kit, because he needs the serial number, which i can NOT find. This engine is 26 years old, it may very well just not be there anymore..<br /><br />Do any of you happen to know the part number for the fuel pump kit I need?<br /><br />Thanks,<br /><br />-TheChad

 

[stan_deezy]

Re: 1979 Mercury 40 HP

serial number is sometimes punched on a welch plug on the side of the engine block: I think right hand side (looking from behind the engine) I think I can see it in your picture although my eyesight may be playing tricks on me