Hi,Great forum that has increased my general knowledge of outboards - and been very helpful addressing a couple of specific repairs.Here's one I can't find using the search function (maybe I'm not using the right search criteria).I have a 1987 Mercury 90hp 3-cyl with oil injection. Doing some spring prep work on the boat and motor last weekend, I visually checked the two stroke oil level in the tank (under the cowling) and made a mental note to add oil before taking it out since is was a little less than one-quater full. There was nothing out of the ordinary.Returning from a week long trip out of town, there is now a puddle of two stroke oil beneath the engine - and the two stroke oil tank is empty.There aren't any visible cracks in the oil tank or oil line - in fact the oil line still has oil in it.It seems my two options are adding more oil to the tank to see if I can spot the leak - or - pull the tank and line for a better inspection.Has anyone run into a sudden leak like this? If so, what was the cause? Does anyone have suggestions before I proceed?Thanks.David
By the way, that tank should be full at all times as long as you have some oil in the main resevoir tank in the boat....So it may not be as sudden as you think...
hello that motor has no remote tank. its either a tank leak or the vynil lines. the lines(all of them) should be replaced every 3 or 4 years. they get hard,rot then break. if you fill it to find a leak be ready to catch any leaking oil or drain the tank again. its unwieldy to remove it when its full.
Thanks for the responses.rodbolt is correct...this Mercury outboard (and at least the ones I'm familiar with) does not have a remote two stroke oil resevior/tank. The oil tank is under the cowling.I bought the boat/motor last spring knowing that regular maintenance was not a high priority for the previous owner. A pre-purchase inspection by a good mechanic showed strong and even compression on all three cylinders. As a matter of regular maintenance, I've replaced the lower unit seals, impeller/gaskets on the water pump housing and cleaned all electric connections on the motor and console and applied dialectric grease to the connections. The motor has been a strong and reliable runner.This leak was definitely sudden. It didn't leak...period. Then within a span of a few days the tank (less than 1/4 full) completely drained onto the cement slab where the boat/motor/trailer are always stored. My first thought was the oil was lower unit lube - whew!, it wasn't.Going in, the likely suspects for the source of the leak were the tank, oil lines or the T-fitting on the botom of the tank. I may add a little oil to the tank before removing it to see if that shows the source. Since I had never seen or heard of this sort of situation, I posted to see if anyone else had and what the leak source turned out to be.rodbolt - the suggestion to replace all oil lines every few years is a good one. Who knows when these lines were last - or ever - replaced.Thanks again for responding. The ice is almost completely out and spring is on the way.
I'm not sure about your motor, but on my 135, there is a tank under the floor (remote) and then the tank on top of the motor. That is a pressurized tank. Apparently, the caps are prone to cracking, which mine did, which made it appear as if it had an oil leak (when trimmed up for storage would leave a big puddle of two stroke oil in the driveway).Might want to just check the cap for leaks.
Thanks, Scott.I replaced the old cap and gasket with new ones right after I bought the boat/motor. At that time, when the motor was tilted up with a full oil resevior the cap leaked oil down the inside of the transom. With the engine tilted down, it wasn't a problem. the new cap and gasket took care of that problem.The leak I'm dealing with now occured with a mostly empty tank (less than 1/4 full) and the engine tilted down for storage. The motor hasn't been run since last fall when it was winterized. It has been stored in a tilt down position since then.
To close this out.....A visual inspection of the tank and oil lines showed nothing out of the ordinary. In the process of pulling the tank, one of the oil lines literally fell apart, breaking into several pieces.After the line was removed and all oil residue drained, checking and cracking of the line were clearly visible on each side of the break point. The line itself was very brittle.I have to count myself very lucky the line did not break while under way when it could have resulted in major damage to the block...failure instead occurring while sitting in storage. Go figure.My guess is that oil lines have never been replaced - and a sudden failure like this is something that I've never seen or heard of before. It really drives home the point that rodbolt made about replacing the lines every few years as part of a regular maintenance routine. Another one of those 'cheap and easy to do - but expensive to ignore' items.Thanks again to those who provided input, it was very much appreciated.
yep having played with this for almost 30 years I have seen many a merc go down due to no maint on them cheesy vynil lines. and most techs are scared to spend the customers money. me its not my money so I dont care. however it is my reputation. so when I get a merc in a grab the oil lines and see if I can break them. if they dont break its ok. if they do I replace them all. much easier to change them before the meltdown than after. the V mercs use a remote pressure tank, the inlines did not.so all you merc dudes with oil injection make a habit to grab the oil lines and flex them. if they wont flex or break when flexing you have a problem.
postscrpt...Start to finish, replacing the oil lines took less than 45 minutes - including a parts run. Total cost was less than five bucks using 'expensive' Tygon brand tubing, specifically made for oil and fuel lines, along with new clamps.If the line(s) had broken under power it would have meant at best being dead in the water or at worst facing a rebuild/replacement of the powerhead.Dodged a bullet on this one. If you have vinyl/composite oil injection lines, take rodbolt's advice and check them as soon as possible.
1987 Mercury 90hp oil tank leak
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