"Cliff, all in all the XR6 ver
"Cliff, all in all the XR6 version was a decent motor.
That's the 2.5 liter block (about 153 cubes), so much better suited to producing the 150 horses compared to the earlier 2.0 blocks.
They can be a little hard on ignitions. The system is sound but they tend to blow switchboxes (and almost always the pair of them if/when they go). But it is a T4 Merc ignition, so excellent except for that little gremlin.
The 2 hours concerns me however. That means lot's of potential "cooties" in the motor. I would definately baby it at first.
Treat it like a new motor and go through the recommended break-in proceedure for sure.
For the first hour running, keep it under 3000 rpms. Second hour running, keep it in the 4000 rpm range, taking her up to full throttle for a minute or two at a time. Then try to keep her at 3/4 throttle (cruise speed) or less for the next few.
After about 10 hours total run time you can run it how you like - until that point it's best to keep from running "wide open" for extended periods unless you don't have a choice.
Additionally, for the first 2 hours or so, I would mix some gas at 100:1 - just until you confirm that oil system is working properly.
On that note - if the oiler is intact I would leave it alone. Merc's oil system is fine, particularly on this model
Would I hang this on the back of my boat? YES, without a second thought. Either a Merc 135 or 150 (XR6 or XRI models only for the 150) would be the top 2 contenders in that horse class.
But mine is just one opinion. And after all it's an Ev 140 looper that pushes me through the water - so maybe not the best ad for a Merc supporter
Seriously though, all round excellent motor..."