1999 Mercury 115 two stroke - 200 hrs. - Any opionons

[Mscanon99]

Hi All,

I am looking at a boat with a 1999 Mercury 115 two stroke, about 200 hours on it. It was used in fresh water and appears to be well maintained, the dealer checked the engine out, all looks good...compression, lower unit, spark.

I am seeking opionions of this motor, good/bad or average?

I have posted before, I was very close to buying a few boats and on the final inspection, they had problems of one sort or another....so the search goes on. This engine is on a Sea Ray, 18 foot, about 2000 lbs (I think including the motor).

I am looking to use this for some spring/fall striped bass fishing in the bays/inlets and to cruise/tube/ski with my younger kids in the summer.

Any thoughts, opinions or first hand user knowledge of this set up would be appreciated.

Thanks.....

 

[MercGuy]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

I have a 1998 115 two stroke on an 18 foot Sea Ray. I bought the boat and the engine as a package, brand new. I now have over 700 hours on the engine and I have never had a single problem with it.

However, to be fair, this is not a universally loved engine.

It is called a 2+2 engine because at speeds below 2000 RPM it runs on 2 cylinders, at speeds over 2K rpm it runs on all 4 cylinders. The engine can tend to miss and studder if you run it at the transition point, as it can't figure out how many cylinders to run on.

I believe that when setup properly these engines run very well, when setup poorly they can be annoying.

Personally, I understand it's design and I've tweaked it so that it runs fine for me. Others hate the design.

If at all possible I would suggest that you take it for a test run so that you can make your own decision.

Cheers !!

 

[Mscanon99]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

Thanks for the first hand review, I sent you a PM to ask a few more questions. I will use the boat for some tubing and my son might try some ski-ing, guess we will have to work around the 2/4 thing. I am more interested in Fishing for striped bass in the spring/fall.

What should the compression on this motor be? Any other area's to look out for on this motor?

Lastly, any reviews on how the 18 foot Sea Ray handles the water? I want to use the boat in the bays/inlets of Central/South Jersey. During the summer I will just use it on the area lakes for some fun with the younger kids.

Thanks

 

[MercGuy]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

I don't know exactly what the compression should be, I'm guessing around 125 PSI, others will probably chime in with better numbers.

I've always been lead to believe that consistancy between the cylinders is more important that the actual number.

 

[CharlieB]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

Another 2+2 owner, works fine.

Most misunderstood system to date, Idles on the top 2 cyls only, no idle circuit in the bottom two carbs.

Ignition is ALWAYS on with the motor running,

Adjusted correctly, OFF-IDLE ALL cyl's get fuel and fire burns. Period.

There you have it. Whatever the idle speed is set at (adjusted by timing advance) THAT is the only time the lower cyl's do not receive fuel and do not fire. When the throttle plates are closed/idle.

The momemt the throttle is moved off the idle position the transistion circuits are uncovered in ALL CARBS, they all get fuel and it is a running 4 cyl motor.

 

[MercGuy]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

Another 2+2 owner, works fine.

There you have it. Whatever the idle speed is set at (adjusted by timing advance) THAT is the only time the lower cyl's do not receive fuel and do not fire. When the throttle plates are closed/idle.

The momemt the throttle is moved off the idle position the transistion circuits are uncovered in ALL CARBS, they all get fuel and it is a running 4 cyl motor.

Charlie,

At the risk of splitting hairs, I'm going to disagree on the finer points of this. Actually, the engine runs on 2 cylinders upto around 2000 RPM, excepting when the driver slams the hammer down.

3 & 4 have a high speed jet, but as you state, no low speed jet. During constant running those cylinders don't fire until enough air flows through the carb to pull a "burnable" amount of fuel out of the high speed jet. That happens at around 2K rpm.

If the throttle is opened quickly (like when pulling a skier up), the acceleration pump shoots fuel into 3 & 4 to fire them until the RPMs get over 2K.

I only mention this so that Mike understands that during times of sustained low speed operation (such as trolling) he will only be running on 2 cylinders, and thereby saving fuel.


No dis-respect intended,

-Steve

 

[Mscanon99]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

Hi Guys....and anyone else that would like to comment.

If two of the cylinders are not running at idle, are they still moving? This is where I am confused on the motor...understanding that its a two stroke motor, is there a potential for the 2 cylinders not running to get scorched because they are not being fed oil with the gas?

Thanks

 

[MercFan]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

Mscanon99, I always had the same question and assumed that these engines must thus be 4 strokes.

 

[MercGuy]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

All 4 cylinders are moving all the time.

During slow RPMs when 3 & 4 aren't firing, enough fuel & oil mix is pulled through the high speed jet to provide lubrication, but not enough to fire.

It's a very, very simple system, with nothing to go wrong.

But, as CharlieB stated, a very mis-understood system.

 

[shes a keeper]

Re: 1999 Mercury 115 two stroke - 200 hrs. - Any opionons

All 4 cylinders are moving all the time.

During slow RPMs when 3 & 4 aren't firing, enough fuel & oil mix is pulled through the high speed jet to provide lubrication, but not enough to fire.

It's a very, very simple system, with nothing to go wrong.

But, as CharlieB stated, a very mis-understood system.

ihave a 1999 and thanks for explaining the 2 4 running.Did anyone ever have a knocking sound she runs 5000 rpm but makes noise between 3000 and 5000 rpm, thanks mark