1994/1995 75HP Mercury

[Walleye #1]

I recently bought a used boat which has a 75HP 1995 Mercury Tiller on it. I had the motor tuned up but it still seems to be a cold blooded motor or just doesn't start as well as it should. Does anyone have this motor and have any of the same issues? Advice? Just looking to see if anyone has any good troubleshooting techniques with motors from this time frame of Mercury.

[Whoaru99]

I've got a 95 or 96 90hp, basically the same motor. Sounds like it runs about the same. Mine always has been a bit rough running as well until you get above 2000 rpm then it runs like a champ.

[jac714]

I have the same motor and it is a cold blooded beast. Is the issue a rough idle? If so I have been told by a couple of Merc mechs that that is the usual behavior of the 3 cyl Mercs.

I know mine runs great as soon as it is warmed up but cold it is a bit rough.

[MarkAlm]

I have a 1997 75hp and it is also cold blooded. A couple of things I try to always do is run non-ethonal gas and I try to always have some Seafoam in the tank as I think this help to run smoother. I change the plugs when I think it is not running just right. I bought this boat in 2000 and no problems. Changed the impeller once.

[Northlander]

Try running Amsoil in it.

[Walleye #1]

Northlander which Amsoil product? Is this basically doing the same thing that Stabill would do?

Also what does Seafoam do for me?

Kind of a novice with motors so any input is great.

thanks

Walleye #1

[herefish101]

if it's oil injected, run the amsoil injector oil, if it's a pre-mix system run amsoil sabre outboard. I started running amsoil two years ago, my motor has never run better.

[marine_man]

They are notoriously cold blooded motors... about all you can do is twist the grip so it's in a higher idle at start up, choke it till it starts (after you prime the primer bulb) and then monitor it.. when it seems like it's about to die push the key in again to give it a little shot of gas to keep it running.

Once they're warmed up they usually run very well.

marine_man

[jac714]

So true MM, once it has been running for a few minutes mine runs like a champ. Idles rough but I can understand that with an odd number of cylinders.

[boatfixer]

After new plugs, timing and syncronizing, running half a can of engine tuner through the carbs while warm and letting it set, I have made a few of them start better. Some are however cold blooded just as marine_man said.

If everything has been gone over and it still starts slow, its possible to tune them so they start better but they will be a little too fat once they've warmed up. Id rather let them crank for a couple of seconds and have it run better warm.

[mojoputter]

Where do they sell the Amsoil injector oil..?

[Ralph Wiggum]

Where do they sell the Amsoil injector oil..?

Mill's Fleet Farm.

[Ralph Wiggum]

If so I have been told by a couple of Merc mechs that that is the usual behavior of the 3 cyl Mercs.

I don't know if that's true of all of them. I have a 1993 60 that's a three cylinder and it is quite smooth.

[mojoputter]

OK, went to Fleet Farm and saw they have the HP injector and the Interceptor oil, which one would be best for a Merc, and can I mix synthetic oil and regular oil together..?

[theoilman]

For your outboard, definitely HP Injector. (Interceptor is for power-valve 2-cycle engines - most 2-cycle snowmobiles.)

[Valv]

You mentioned:

it still seems to be a cold blooded motor or just doesn't start as well as it should.

What other motor are you comparing to? Some newer fuel injected and/or 4 stroke motor start with just a touch of the key, some older carburated motors like yours needed a little more "care" to get them started especially when cold.

[Ralph Wiggum]

I've been satisfied with HP Injector in my Merc.

[pulleye16]

Totally agree with everyone else...VERY COLD BLOODED. Mine has a rough idle and very tough to start but I've never had "problems" with it. By tough to start I mean I have to prime the bulb and choke it everytime but It will ALWAYS start right after that. Even If i run all day, I still need to prime or choke it.