Mercury 5000, start at home, won’t start at lake.

[Nandy]

Mercury 5000 - 50 H.P. Four <br />4 Stroke<br />Motor s/n 2479050 <br />Motor built somewhere from 1965 - 79 Possibly 1974<br /><br />I had this motor for over 3 years. It always dripped water on the water exhaust port instead of shooting the most common know tattletale stream of water that most of us are use to. I thought it was the water pump. I purchase an impeller kit, installed and it will still just dripped. I researched the net and all I found was one person indicating that this was normal for this motor type and model. Last year next to the end of the season the motor did a very loud noise and stopped. It would not start again. I took it out of the water and realize that the exhaust port did not looked wet. Next time at the water the motor started ok. I look at the water exhaust while running and realized there was no water coming out.<br /><br />I took the outer exhaust plate and the inner exhaust plate out. The grooves on the outer exhaust plate were plugged with some rock like material. There was no way that the water was flowing there and coming out of either water exhaust. Anyway, I scraped the material out, put everything together with new gaskets and fire the motor with the flush attachment. No problem there, it worked like a charm, water coming out of the exhaust port like any other motor. I speed it up for short period of time just to see how it worked. I also put it on gear to make sure the shift’s were working fine. I took it to the lake and there it would not start. I could see some smoke coming so I know there is some combustion. At some time the smoke appeared to come out of the lower carb. After almost draining the battery down the motor started just to die 2 seconds after. Took the motor back home and there it start on the second try. Take it back to the lake and it wont start, take it back home and it starts. Checked all over. Take it to the lake, no start. Checked there and keep trying to started. It started only when the motor was out of the water with only the prop and the water pump ports under water. It ran for about a minute or so and when I tried to accelerate it the motor died. Did this number a few times, took it home and there with the flush attachment it worked great, it will not die if I accelerate it and will not stop running.<br /><br />I am at a lost. While working on the motor initially I had it upside down for a while. I am wondering if I messed up the carburetor float but this will not explain why it won’t run at the lake. Maybe it is the reed valves but I never touch them. I am using new gas and I am adding the gas stabilizer like always. There is spark on all plugs. If I check the plugs when it fails to start the plugs at the top are wet and the ones at the bottom are dry. However the lower carburetor seems to “spit” gas out when running. Any help will be appreciated. Sorry for the long post.

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Did I post too much information or too little. Let me know if I need to change the original post. I really need the help.

 

[Virago85]

Re: Mercury 5000, start at home, won’t start at lake.

Sounds like your geting water in to some of you cylnders when you back the bout in to the water <br /><br />I would try this raise motor all way up back in water slow then i would lower moter all the way down but dont let your exust ports go under and try to start motor

 

[robnik1]

Re: Mercury 5000, start at home, won’t start at lake.

what kind of compression do you have? When you run it on the muffs at home you have no back pressure, when at the lake and in the water you will have back pressure, not to mention loud noises and hot motors usally mean bad things, hope not but just a thought. <br />Good Luck

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Virago85, thanks for the input. I though about that and made sure the motor was high enough to avoid water comming in. Any other idea?<br /><br />Robnik1, I have not checked the preasure. I probably need to. I have been partial to think it might be the reed valves. It is easier to check the cylinder preasure.<br /><br />Any more ideas will be welcome.

 

[robnik1]

Re: Mercury 5000, start at home, won’t start at lake.

Think we would see fuel mix spitting out carbs if reeds bad, but maybe not, guess it would depend how bad?

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Well, actually the lower carb does seems to spit some gas. It's probably been doing this for quite some time since I always saw some fuel under the carb. I notice the tiny dropplets when working this "new" problem. I hate to take this motor appart again. I was hoping it would not be the reeds, but it looks like they need attention anyway... Will try to get a tool from advance autoparts to check the pressure of the cylinders. BTW, I could not find the pressure value that I should be reading. The book only mention that the difference between the cylinders should not exceed 15 psi. Anybody has the actual psi that I should be reading?

 

[papasage]

Re: Mercury 5000, start at home, won’t start at lake.

i dont have a manuel here but the 65 i have is a 1974the comp. is 125 lbs on each cylinder . i think 100 or moore not to have a difference of 15 lbs. papasage

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Thanks Papasage. I am checking the prices for the parts on these motors. I might also need to check if I can find this same motor on a marina. Just to have some options open...

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

will I need a special adapter for the presure gauge? Should I crank the motor manually or with the starter?

 

[Backlash]

Re: Mercury 5000, start at home, won’t start at lake.

It sounds like the lower carb is not supplying fuel but I'd run the compression test first. If it checks out OK, pull the carbs and thoroughly clean (soak) and blow out with compressed air. While you've got the carbs off, check the reed valves. The spitting you describe could indicate bad reeds also. Let us know what you find.<br />Backlash

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Thanks Backlash. I am having problem getting the cylinder pressure gauge. Looks like every gauge is already loaned. If I can't get one loaned I will have to buy one.

 

[Fishin4fun]

Re: Mercury 5000, start at home, won’t start at lake.

a compression gauge is a great investment. I have always had one for my outboards and check my compression each spring when I am bringing it out of hibernation, just to make sure things are not going south on me. I was told that often you can see the problem coming before it causes expensive repair bills by monitoring your compression each season, (more often if you use your boat a lot).<br /><br />Only my opinion....

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Well, from the top to the bottom the first 3 measure 130, the fourth is 15. So look like I might have a nasty surprise when I open this motor. Now, can somebody explain me why will that stop me from starting on the water and not stop it from stop out of the water? It just do not makes sense to me.

 

[Old Jarhead]

Re: Mercury 5000, start at home, won’t start at lake.

Just a guess... <br /><br />When you start the engine with muffs there's no back pressure. This may explain why it starts out of water??

 

[schaiss]

Re: Mercury 5000, start at home, won’t start at lake.

When your LU is submerged at the lake, the water pump is capable of delivering pressure at a faster rate. With the low compession you indicate on cylinder #4, it sounds like your pumping water into that cylinder through a head gasket leak ( and these engines we run do need water, but not in there!) Get that head off, find the leaker and fix it, and you should be on your way to your favorite fishing spot!

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

I will start on it probably Sunday, I will be turkey hunting tomorrow. I have a friend that used to fish on my boat with me. He bought a boat this last season and I will be going with him until I am done here. When I fixed the water issue I tried to get the cylinder gasket out to replace it. The bolts were stuck with rust and all. I broke 2 bolts and had to replace them. I am affraid that the same thing will happen to the other bolts. But it has to be done. A lot of rust buster, hammering and heat on the way! Ohhh well.<br />Thanks for the help guys, I will keep you all posted.

 

[emckelvy]

Re: Mercury 5000, start at home, won’t start at lake.

50 HP Mercury does not have a cylinder head. The tops of the combustion chambers are integrally cast-in to the block. The cover you see at the back of the block is just a water jacket cover.<br /><br />Your #4 cyl is shot and you'll have to pull the powerhead, split the crankcase, and remove the entire crank assy to effect a repair. Pay special attention to the bottom seals, as typically a failure in #4 may indicate something going on down there such as a bad seal allowing water to be sucked in.<br /><br />Check all the pistons as you may have problems elsewhere that haven't shown up yet.<br /><br />You can remove the powerhead and take it apart with out the use of special tools, except for pulling off the flywheel. Either use a Mercury flywheel removal tool, or remove (2) bolts opposite of each other on the inner flywheel hub, and use an automotive harmonic balancer puller and Grade 8 or Better bolts to get the flywheel off. Of course don't forget to loosen the crankshaft nut first! Don't remove the crank nut fully, as the flywheel may come off with great force and konk you in the head!!!<br /><br />Best bet would be to purchase a Seloc manual so you'll know what you're up against. Lots of pictures and "Good Words" for the prospective mechanic.<br /><br />HTH and Good Luck...........ed

 

[Nandy]

Re: Mercury 5000, start at home, won’t start at lake.

Thanks for the advise Ed MC. You are right, it is the "cylinder block cover" what I was refering to. I was calling it the other way since my "mechanic" experience is from working on cars. I do have the SELOC manual. It has proven a definite help. Sometimes I find it lacking of information though, but it is a whole lot better than nothing. <br />A lot of people will be surprise how many people will try to get that flywheel out without removing the nut first. LOL. Thanks for your input.