I was out at the river seven days, last day my exhaust manifold(Log) decided to melt down. I have a couple of question for the experts as I am new at having a jet boat.

1. Why did my log break down? I am assuming age but I just wanted to see if the experts agree.

2. I bought a used set of logs, he said they were harmins, not sure how you can tell but I will attach a picture. My old logs have two hose connection in the front of the logs and one connection coming out of the rear of the logs. The new(used) logs I purchased have two set of connections up front and two in the back. I am assuming that they are both outlets for water and they should both be hooked up? Just wanted to get some feedback from the experts before I fix the boat. I am new to jet boats so anything you guys could offer I would appreciate. Thanks Derrick