I Got Me a Mercury !!!

[GA_Boater]

Re: I Got Me a Mercury !!!

If it takes 4-5 pulls to get her started, the unburned fuel from the first few yanks will end up in the water. Is there some extra smoke when she starts?

 

[tpenfield]

Re: I Got Me a Mercury !!!

If it takes 4-5 pulls to get her started, the unburned fuel from the first few yanks will end up in the water. Is there some extra smoke when she starts?

No real extra smoke or anything noticeable. Just pukes a 'sheen' on the water once it fires up . . . does it for a second or two, then seems normal.

I'm thinking that I will do some carb cleaning and maybe have a look at the spark plugs, run a compression test, etc. If the compression is low, that maybe why it takes a little bit to get it going.

 

[tpenfield]

Re: I Got Me a Mercury !!!

Quick Update:

I did some test running and diagnostics on the engine tonight to see if I can ID and remedy the oil slick when starting issue.

I ran the engine for about 20 minutes, then pulled the plugs.

Compression is 95 and 97 psi

Spark plugs look good, no fouling

I ran a heavy concentration of carb cleaner in the fuel.

After a while the engine would not stay running . . . seems to stall out after about 5 minutes of running.

I think that I should clean all of the electrical connections, etc. It may be an ignition problem that accounts for the hard starting and stalling.

 

[jbjennings]

Re: I Got Me a Mercury !!!

If I recall correctly, the fuel pump is integral to the carb in those motors. The little check valves in the pump can easily get clogged with particles of rubber that are rotted out by the ethanol in today's fuel. That may be the problem with it dying. THe bowl may not be staying full of fuel due to a clogged fuel pump. I also would clean the carb for sure. Your idea about cleaning all the connections is right on---it could save some of your electrical parts from increased resistance even if it's firing presently. Also, be careful the wiring is all good. The wires can look good on the outside, but the copper could be rotten on the inside.
Good luck,
JBJ

 

[tpenfield]

Re: I Got Me a Mercury !!!

I *think* that I found the problem . . . or at least a problem. As I was cleaning up the wiring connections this morning, I noticed that the harness to the shut-off switch was really deteriorated . . . kind of crumbly. Probably shorting out the ignition. . . .



So, I am making a new wiring harness and will probably need to replace the shut-off switch as well. Looks like I'll be rowing for the next few days.

 

[GA_Boater]

Re: I Got Me a Mercury !!!

Vintage Merc wiring - Gotta love it. Use plenty of heat shrink tubing and liquid electrical tape.

 

[tpenfield]

Re: I Got Me a Mercury !!!

I made a new cable harness today and replaced the push button kill switch with a toggle switch.

The engine seems to run fine now . . . I will be testing it in the water tomorrow to see if it remedies the oil slick issue.

Here are a couple pic of the new cable harness and kill switch. I soldered the connections . . . still gotta do the liquid electrical tape.

New cable harness that I made from some spare marine wire that I had lying around. . .



Here is a view of the new kill switch . . .

 

[GA_Boater]

Re: I Got Me a Mercury !!!

I see it's been evaluated and approved.

[URL=http://s1184.photobucket.com/user/sv29n/media/Cheap%20boats/tpwiring.jpg.html] [/URL]

 

[tpenfield]

Re: I Got Me a Mercury !!!

Yup, the engine seemed to run better now that the wiring has been replaced, and the ignition shut-off works much better too :thumb:

Still seeing some oil/fuel at start-up . . . does not quite seem as much, so I will monitor it over the next week or so. If it persists, then I will probably take a closer look at the lower unit.

 

[tpenfield]

Re: I Got Me a Mercury !!!

A few more thoughts regarding my 1969 Mercury 7.5 hp engine in terms of the oil/fuel discharge/slick issue . . .

Just trying to think of various possibilities that could be contributing to the brief, but noticeable discharge of oil/fuel when the engine is starting:

I noticed that the plug gap seems a bit small. I did not measure it, but it looked to be under 0.030" If it were too small of a gap, I am thinking that the spark might be too small.

I am wondering if the engine crank shaft seals are getting worm (or drive shaft seals) is there a path where oil would drain from the engine into the exhaust duct or water intake?

I am also thinking that if the carb bowl was overflowing a bit during priming, that may be discharging through vents in the engine cowling.

Also, still considering lower unit/prop shaft seal issues. I notice that if I the engine sits for a while tilted up, it discharges more. If I leave the engine down in the water not so much. Also, the longer it sits, the more discharge during the starting process.

the funny thing is that I do not notice much of a slick when I have run it at home in my trash barrel. Could it be a salt water versus fresh water thing?

TIA for any comments or insights.

 

[matt167]

Re: I Got Me a Mercury !!!

I've heard that the old Mercs will drip from the carbs when they are primed, so you will always make a small fuel slick when starting them.. I wouldn't know personally. I've never ran an old merc and I still have not tried to start my 650

 

[tpenfield]

Re: I Got Me a Mercury !!!

Yea, I'm gonna check out the carb overflow theory and see if I find fuel in the lower cowling.

 

[tpenfield]

Re: I Got Me a Mercury !!!

Quick Update:

I found oil on the leading edge of the lower unit this morning. The engine has been tilted up since Sunday . . .

So, I'm thinking the oil slick issue is more of a lower unit issue rather than and engine issue. I did not see any obvious signs for where the oil could be leaking . . . seems to be very slow. So, I guess I'll re-check the lower unit oil at some point to see if I have water in there. Based on where the oil seems to be originating, it almost looks like it is seeping from the joint where the lower unit mates with the mid-housing (or what ever it is called). Maybe an internal seal issue :noidea:

Thoughts? TIA

BTW - I tweaked the spark plugs a bit and the engine seems to start fine. I got 14 mph out of the thing today, up from the 14 mph I was getting before (gps)

 

[tpenfield]

Re: I Got Me a Mercury !!!

I think I found the source of the oil slick . . . It looks like oil is slowly leaking from the seam where the lower unit mates to the shaft.

Here is a pic of where I found the oil seepage, it tends to travel down the leading edge of the lower unit.



I'm not familiar with what is inside this area . . . all I know is that the impeller was replaced not too long ago. So I am assuming that the lower unit has come off recently.

Thoughts? Advice ? . . . . TIA

 

[matt167]

Re: I Got Me a Mercury !!!

On one of the bigger Mercs, the shift shaft seal is in that area, and it probably is on the little Merc 75.

 

[GA_Boater]

Re: I Got Me a Mercury !!!

Probably item 44 here. Mercury Marine 7.5 HP GEAR HOUSING(PROPELLER SHAFT) Parts

 

[tpenfield]

Re: I Got Me a Mercury !!!

Thanks guys . . . I'll order one and see how I do on taking the lower unit off, etc.

Any pointers ?

 

[GA_Boater]

Re: I Got Me a Mercury !!!

I've always heard to make sure you don't pull the shift shaft out accidentally.

 

[jbjennings]

Re: I Got Me a Mercury !!!

That prop shaft likely has several shims and such on the gears that must go back in the same sequence/position, so be careful to remember where they go. I would put the shifter in forward before I took the lower unit off. It is hard to keep the shift shaft in neutral when reinstalling the lower unit because it tends to rotate into forward. If the shifter is in neutral and the shift shaft is rotated to forward when reinstalling, the lower unit won't shift correctly. The bearing carrier retainer is left handed threaded if I recall correctly. It's been a while since I worked on one. I would NOT mess with that lower unit if the oil inside it looks good. If the oil looks milky or has water in it, you might as well reseal the whole thing while you're at it. Don't do just the prop shaft. The prop shaft and drive shaft could easily have grooves where the oil seals have ridden for so many years. YOu may try to shim the seals where they're not riding in that groove. Hopefully that mild steel drive shaft is not pitted in the seal area like a lot of them are. I've heard you can EZ-sleeve the shafts but I haven't done one myself. I'd think that would be a good idea if the shafts are excessively grooved or pitted. The mercury forum would be super helpful..... several mercury experts that frequent that forum.
Good luck,
JBJ

 

[tpenfield]

Re: I Got Me a Mercury !!!

Update:

The engine really started puking oil yesterday, so I pulled the engine off the boat and brought it back to my house for repair. In a sprint of motivation, I took the lower unit off last night. Seeing how these things come apart and go together is an education. There was a fair amount of oil living inside the casting pockets of the lower unit, and it looks like it could easily discharge through the exhaust port/prop or via the seam where the lower unit mates with the shaft housing.

Anyway, here are a few pics.

Lower unit . . . .


Motor without LU


Closeup of LU . . . pretty decent design for 1969 . . .


I set the lower unit at an angle similar to the 'tilt-up' angle that it would be on the boat and left it over night. There was some oil seepage this morning, but it was hard to tell exactly the source. Probably the shift shaft seal, but not completely obvious at this point.

So, I have now set the LU inverted to see if I can ID and oil drip more precisely.


I'm still searching YouTube for a video of replacing the shift shaft seal. Mostly water pump/impeller replacements that I have found so far. I might have to get a maintenance manual and actually read the instructions