"Bryan, so many questions [img
"Bryan, so many questions [img][/img] - will just warn you in advance, my answer may be a little long...
First off, that is a 1985 "XR2" model.
Many parts are still available from a Merc dealer.
Unfortunately, the t/t pump motor (and most of the assembly) has been long discontinued. You could however, retrofit a later model design, but will likely require changing the entire unit, not simply bolting on another trim motor.
Since the motor is about 25 years old you have to assume that at some point over all those years it may have been neglected.
Did you have the motor checked at all before or immediately after purchase?
At minimum I would have a compression and leak down test done on the cylinders. Pressure test the lower unit.
Unless you have "proof" of service, change the spark plugs, the impeller and lower unit gear oil.
The hard starts could simply be old plugs or old gas or could be a warning of a clog developing in the carbs or a fuel pump on the way out.
Oil mix - this model originally had oil injection. Is it still there? is it functioning? a marine tech will also be able to advise on that.
If you don't know, then run it at a 50:1 mix until you can confirm.
Your water pressure sounds ok and if the motor is not overheating your tell tale could simply be blocked (bugs like to make homes in any opening).
Your max rpms is 5500, you need to select a prop that will allow you to get to 5300 rpms (give or take 50 or so) when you are using the boat as you normally will.
That means "loaded" the way you will use it. The prop could be significantly different from what the previous owner required.
You may run heavier or lighter, in different water conditions - may "cruise" more than run flat out. Those and numerous other differences will dictate what you should run so you need to do some trial/error testing.
Each 1" change in pitch will result in a change of approx 200 rpms - so load up and take her out (when the motor issues have been addressed and she is tuned up).
If she will only get to 5000 rpms then go with 1-2" less in pitch - if it gets to 5600, move up 1" in pitch etc...
This was a decent motor in it's day and it could well have many many more years of life in it yet.
The basic design stayed in production for many years finally ending it's lifespan as the 135 Merc (the 135 and some 150 models shared Merc's 2.0 liter powerhead until production ended about 5 years ago) which is why there is still excellent parts support through Merc.
Should it require it, this motor is an excellent candidate for a refurb or rebuild.
That may not be something you considered when you bought it (the requirement for a rebuild) but you have to consider, since it is 25 years old it may be "tired".
If you are mechanically inclined it can be done for about 1000 bucks - a shop will charge about 2500. But when you compare that to the cost of a new 150 (12K or better), that could be a cheap way to get 15-25 more years from the motor...."
A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)