Re: Merc 7.5 Carb and Lower End
Originally posted by Axeman:<br /> Hi there.<br /><br />I have a Merc 7.5 and it has been sitting for a year or so. After not being able to start it I took the carb off and looked in the intake.<br /><br />The venturi was twisted around and I am sure that was not helping so I took it out and sure enough the two tabs that normally hold it in place were broken off.<br /><br />I have the new part on order. So my first question is which way does it go in? With the rounded end pointing towards the engine and the flat end pointing towards the air intake? I went to a dealer and looked at their "exploded view" to see if I could tell and I cant.
go to mercruiserparts.com and look at their exploded views. It might show you, although I doubt their graphics are better than the parts guy at your local dealer. You'll need info on your motor such as serial number and maybe the type of carb. If you can't tell, I'd ask the guy in the repair shop of the place you buy the venturi.<br /><br />This and all your questions below will be answered if you buy a service/shop manual for your engine. I recommend it. I have both a Seloc and a Mercury shop manual for my 110/9.8 hp (both also cover the 7.5) and have found both adequate for basic carburetor and lower unit maintenance (see below). You can probably get either or both at your local dealer and there are many on-line sources.<br /><br />
My other question is regarding the lower end. Is it supposed to be full of gear oil or someting? Where would I check the level of fluid and what other tips can anyone give?
There are two screw plugs - one for filling and the other for venting and checking the level of the oil. The shop manual will show you exactly where the screws are. You drain by removing both screws. You fill by pumping oil into the bottom hole until it comes out the top hole. You inspect the old oil for signs of water intrusion and metal flakes. You use marine-grade gear oil which you can pick up at the dealer or at any place marine oils (e.g. the TCW3 50:1 oil you're using) are sold.<br /><br />
I have only had this motor for 3 years. Ran it for 2 summers and then stored it for over a year. So I have no idea what maintenance the old owner did but I want to make sure I am doing everything to keep this sucker runnning. The carb looks very clean and I thing the venturi will solve my starting problem but I want to avoid any others.
To me the most basic maintenance, especially for a motor with unknown history, is to change the water pump impeller, change and check lower unit oil, change and check spark plugs (make sure you get the right ones in there - the ones in there from previous owner might not be the right ones), clean and re-build the carburetor. All covered in the shop manual and easy to do.<br /><br />
When I first got it I ran it in a big bin in the back yard when I changed the sparks etc and the water in the bin got quite the scummy oily layer in it. so I am not sure if it might be leaking etc.<br /><br />any help would be apreciated.<br /><br />Thanks
With a 2 stroke outboard, the exhaust contains alot of fuel/oil mixture residue - and most of the exhaust comes out under water through the prop. Therefore if you run it in a barrel, it's normal to get quite an oil slick on the water, even sludge if you run it enough.
<br /><br />I am hoping that when I put it in, that the hole for the fuel spigott will only line up when it is in one way and not the other. casue that would be easy