I understand what it's like to trust someone and end up in that situation. It's a hard lesson, you can't just rely on the seller's word. I've been in that situation a couple of times myself, but life has taught me that.
I have recently met a similar situation and concluded that the low compression numbers for the port engine, especially the 150 PSI reading, are a cause for concern. This suggests a potential problem with that cylinder, such as worn piston rings or valve seals. I have done a leakdown test to...
The maximum voltage you can expect to see for a typical 12-volt automotive electrical system is around 14.7 volts. This voltage is produced by the alternator, which is responsible for charging the battery and providing power to the electrical system.
I have found on the Internet the following...
Try disconnecting the battery from the outboard motor, removing the cover from the throttle control, and disconnecting the throttle cable from the throttle drum. Then remove the screws that hold the throttle control in place and carefully remove the throttle control from the outboard motor.
I think the cause is clogged cooling passages in the outboard motor that can become clogged with debris, such as sand, seaweed, or rust. This can prevent the water from flowing properly and cooling the engine. Try checking the cooling passages for any debris that may be clogging them.