TOPIC: Merc 700 oil in test tank

I need a bit of advice. I started my Merc 700 6 cyl. Gear shift this weekend and after a half hour run there was quite a bit of oil in the water drum, what would cause this? Also a bit of oil seeping at the crankshaft cover joint behind the starter. Otherwise all went well. I don't know how long this motot had been sitting but it started right up and ran well. Water was flowing from the telltale but I am unsure of the intake location.
My G3 is just about finished, just need upholstry and rub rail strip. I a anxious to try it out as soon as the engine is squared away.
Thanks for all your help, Jim

Is it just from oil coming out the exhaust into the water. That doesent alarm me but I'm still new to the Merc monsters.

I wouldn't be concerned about the oil in the water. It is natural for these old girls. Being 2 cycle and thirsty, there is oil and gas that is not all burned. It is more noticeable when running it in a small container like a barrel. As for the oil on the block, is there one of the rubber pressure equalizing tubes near there? They can leak around the connection to the block or they can have a crack. There also is a possibility it may be coming from the top carb, either from the throat or elsewhere.
Bill

If it indeed is coming from the crankcase joint, the correct fix would be to pull the powerhead, remove the crankcase cover, and re-seal.

The original sealer is Permatex or similar and I've seen plenty of them leak after 50+ years!

If you use an anaerobic sealer such as Permatex 518 or OMC Gel-Seal, it'll never leak again.

www.amazon.com/Permatex-51813-Anaerobic-Gasket-Maker/dp/B0002UEONM/ref=sr_1_1?ie=UTF8&qid=1395690108&sr=8-1&keywords=permatex+518

NAPA sells this as well, amongst others.

Mercury also sells what they call a "Master Gasket" kit which contains a tube of 518 plus a primer spray which cleans & speeds cure time.

I've had great results using the 518 sealer by itself. As long as you degrease the flanges the 518 will cure just fine.

Obviously this isn't welcome news after doing so much restoration work, but if you didn't split the cases, it certainly could be the problem.

You might be able to thoroughly degrease & temporarily seal the leaking area with some Permatex Ultra Grey, which will hold up to gasoline a bit longer than standard RTV. But of course that's not something you'd want to leave for long-term.

Anyway, hope the problem is elsewhere, but best to be prepared for the worst-case-scenario.

HTH.........ed

don't use to much a ONLY VERY THIN COAT is what is needed.

Will a crankcase leak affect the performance of the motor or cause damage?

If the leak is pronounced, yes it will. The crankcase must be sealed airtight, and if a leak is present it can lean the mixture in one or more cylinders causing nasty internal damage. I would pull the powerhead and reseal with new O rings, seals, and gaskets. Cheap insurance, and to neglect it is to do so at your peril.

Is the lead seal still on this block ?--Any sign that someone had it apart before ?----My own opinion is why do all the paint work without taking a block apart.---These motors usually do need some internal inspection / work.

Yes, there is a leaded sealing wire thru a stud below the starter. I will going to remove and resealing the motor. I haven't found a gasket set yet so I'll wait till I have it in hand, maybe next week.
Thanks, Jim

Since you're going to do the job, you may as well plan on replacing the lower crankshaft ball bearing; you're gonna have to drive it out of the lower bearing carrier anyway, in order to get at the lower crankshaft seals.

Be sure to check the upper bearing as well, although you can do an R&R on the upper crankshaft seal without pulling the bearing out of the carrier.

Both upper and lower bearings are a common "6206" bearing and as long as you get a name-brand, quality bearing, you don't need to pay big $$$$ for the Merc part number.

NAPA amongst others will probably stock the bearing in a "BCA" or "SKF" flavor. Other good brands would include "FAG" & "NTN".

There are a ton of cheap bearings on eBay, but most of them come from China and are inferior. I've found decent deals on name-brand bearings there, too.

One tip for removal of bearings pressed into the aluminum carrier, take a small torch (propane, MAPP, Presto-lite) and heat the O.D. of the carrier around the bearing; usually the aluminum carrier will expand much faster than the bearing, and the bearing will fall right out. Or, it'll be a much easier to drive out. Be sure to wear leather/heavy gloves!

G'luck with the R&R & keep us posted......ed

Ed, Thanks for the advice. I might try to match the seals also, there's a Motion Industries store near by. Do you reccomend that I remove the exhaust cover. The motor did run good with a good stream of water. There was a little bit of exhaust from the rectangle hole behind motor.
This is the first outboard I've ever owned so your help is greatly appreciated. My experience is with heavy equipment so this is a new game for me.
Thanks, Jim

If there are no external leaks, and you didn't see any moisture on the spark plugs, I'd leave the exhaust cover be.

The 700 has a stainless flat inner exhaust plate which isn't prone to perforation, so unless the gaskets were leaking it might be better to leave well enough alone.

The other issue with pulling the exhaust manifold cover is whether or not the 1/4-20 bolts will come out without breaking. If your motor was a Salty Dog, those bolts are probably stuck in there forever without drastic heating and other extreme measures.

That being said, if the bolts come out easily and you could find a good source for those getting-very-hard-to-find gaskets, it's a good time to do it, since it's darn difficult (if at all possible) to get at those bolts with the powerhead in place.

If you renew those gaskets, they'll go back together dry or with a very thin coating of 518 if you really want to splurge. Spread a thin coating of Permatex No. 3 on the manifold bolts and torque to 70 inch-lb for 1/4-20 bolts.

Glad to help, that's what we're here for!

G'luck with the repairs........ed

Jim;
If you need gaskets for that I have them NOS. Email me This email address is being protected from spambots. You need JavaScript enabled to view it.
Tim

Good evening! I have the motor out and crankcase split in half, not to bad of a job. I did find a few things that didn't seem to be covered in the service manual, I might have removed a few extras but it only goes back to gather one way. I wasn't sure of distributor and drive removal and it was a struggle to get the plug wires thru the bracket on the exhaust cover. Also the fuel line system seems to be built as a unit because the carburetors need to be removed and unscrewed one at a time. I think this is a good time to replace all the lines. I also noticed the top bearing was very dry and "gunked" up with dry fuel mixture. I could not turn it by hand after removal so I cleaned it and it ran free but was a little rough. Again a good time to replace both bearings.

I'm glad I took the advice to repair the leak and get to know these motors, I have a few more get going for use on boats I have gathered up. I'm going to get some parts books to supplement the Service manual as it's would be helpful to see a complete break down.
Thank you all, Jim