Mercury 115 Option to switch from oil auto blend to mix in

n8ve1

Cadet
Joined
Aug 22, 2012
Messages
14
Hello, I am farily new to boating, going on my second year now. I have a 1991 Sea Ray 160 OB with a Mercury 115 with the auto oil mixing on the engine. To make a long story short I took my boat in for a preseaon and was told that #4 has only 30# in it, bad news right? So it comes down to a $1600 to $1800 rebuild and replace of that piston with unknown cost of what they may find. I got my boat back and spoke to another shop and they have a few older merc 115s, said one was recently rebuilt. They also told me I may be better off with an older mix it ur-self engine, since the auto ones tend to burn out pistions usualy the #1.

So the question is rebuild my current 115 or retro to an older 115? Need some input on this. Are some years better then others on the older Mercs? Will the controls, tilt & trim be an issue?

Thanks.
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Mercury 115 Option to switch from oil auto blend to mix in

The 115 is a great engine the older ones are prone to insulation falling off the wires so make sure the engine they are trying to sell has ADI ign.(6 coils)the auto blend was so bad I can't believe there are any left out there running as the destroyed everything they were on.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Mercury 115 Option to switch from oil auto blend to mix in

The automixer mixes oil into the fuel for all cylinders. There is no way would deprive one cylinder of oil. More likely you have a clogged carb or an overheat issue. Whether you decide to premix is a personal decision, but donj't blame the automixer.

Older 115HP motors tend to be inline sixes. Althought they are/were a good design, they are pretty outdated now. You will want to go newer.

Throttle and shift cables will work. Elec wiring may need to be adapted....
 

n8ve1

Cadet
Joined
Aug 22, 2012
Messages
14
Re: Mercury 115 Option to switch from oil auto blend to mix in

Thanks for the input from both of you! If I decide to go a bit newer, what years should I be looking to start at?
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Mercury 115 Option to switch from oil auto blend to mix in

1978 or newer
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Mercury 115 Option to switch from oil auto blend to mix in

Go to a newer Merc that has the PTT between the transom brackets. At this point, stick with a mid-90s or newer motor.
 
Top