Mercury 115hp inline 6 newcomer

[smike26]

Just got a boat with a '78 Merc inline 6 115hp. I've been reading through the forums and am pleased with all the positive things I've read about this motor. I'm a mechanic by trade but boat motors are new to me, so any tips, tricks, comments (positive or negative) would be greatly appreciated. Even things you might consider insignificant go ahead and throw at me, it might help me down the road.<br />thanks alot.

 

[Franki]

Re: Mercury 115hp inline 6 newcomer

1. Change your water pump impeller if you just got the motor, and check it again a year from now.<br />2. Get a manual, very handy..<br />3. Run it at 50:1 premix.<br />4. Decarb it once a year.<br />5. Go fishing.....<br />6. enjoy.<br /><br />rgds<br /><br />Frank

 

[Gold Bear]

Re: Mercury 115hp inline 6 newcomer

smike26 <br /><br />Actually, your particular engine will last longer if you will mix the fuel / oil at 40:1, ie. 5 gallons of gas per bottle of oil versus 6 gallons.<br /><br />Your engine is very susceptable to damage from preignition. Make sure the total timing does not exceed 21 degrees. You should also consider using mid-grade or premium fuel. <br /><br />As already mentioned, get a manual (the factory service manual is by far the best) and check the lync & snych adjustments of the throttle mechanism.<br /><br />Never use starting fluid. If the engine is difficult to start (often first time in the morning) carefully use a squirt bottle of pre-mixed fuel to prime each carb. First make sure the choke mechanism is working the best it can, and hopefully you will not have any cold start problems.<br /><br />If you don't already have one, install a glass in-line fuel filter so you can make sure there is no trash in the fuel line.<br /><br />Pull the bottom oil drain screw in the foot and make sure there is no water in the lower unit. Just pull this screw long enough to see if the oil is clean. After you confirm it is ok, pull the top (vent) screw and make sure both have good gaskets so they will seal properly.<br /><br />Always visually check the tell-tale spray from the water pump when you first start the engine to make sure it is ok. On occasion, when operating the boat, look back and make sure it is pumping ok.<br /><br />It is important for your engine to operate at close to 5,400 rpm's at wide open throttle. The WOT will depend on you boat, and the load it is carrying. Get a tach, put a normal load in the boat and test the WOT rpm's. If it is not in this range you will have to consider changing the prop. There are a lot of post here at this forum discussing this procedure in great detail. If you find this is necessary do a "Search" and study up before choosing another prop for your boat.<br /><br />Also, as mentioned, perform a "decarb" about twice a year, your engine will thank you for it in lifespan, and increased performance. Again, that subject is discussed at length.<br /><br />(I have a 1971 model that runs like a top).<br /><br />Welcome to iboats!!!<br /><br />Gold Bear

 

[93bronco]

Re: Mercury 115hp inline 6 newcomer

one of the down sides is the reed valves are on the crank, if they need to be replaced the case has to come apart. the other is <i think> this year is still one that has the cylinderhead is incorporated into the block. if you shed a ring or some thing similar you just cant replace the head. i got rid of a 1975 and 1977 1150 for those reasons. that was just 2 reasons the 3rd was i needed a 25in shaft motor and both 20in. probably would have kept them if the shaft was correct.

 

[smike26]

Re: Mercury 115hp inline 6 newcomer

thanks to all that replied. You people are awesome.