Re: mercruiser 165 hp 4 cylinder
Search will help as there are a ton of threads.
There are some here who will trash the motor out of hand and others will tell you it has its issues but they are known by now and are reasonably easy to work around and look out for.
In earlier models the heat exchanger was 3". These tended to run hot and any overheat in a 470 is bad news due to the aluminum block and iron head causing a leak. Mid model on they had 4" heat exchangers which are well regarded.
They also came with an outboard style stator and raw water cooled voltage regulator. This system was prone to failure and expensive to repair. If it has not already been done, you can easily upgrade to an alternator for 100-500 bucks depending on the kit.
They also had a tendency to leak water out of a cam seal in high time motors but there is a 20 buck speedy sleave fix that resolves that.
On the plus side, they have a great power to weight ratio and have a lot of torque and are known for good mileage. They are also about 300 lbs lighter than their modern replacements, the 4.3.
In summation, if you are mechanically competent they have some significant upsides. If I'm missing something, I'm sure others will chime in.