I was rinning my 98 200 OceanPro the other day, and it developed a problem with the gearcase. I was palning along about 3800 rpm and the started to develop a "clunk", then return to running normal, it would do it again about every 40 seconds.
It sounded like the gearcase wanted to lock up, but was running too fast to stop the powerhead.
I backed off the throttle, and it went away. I discovered the motor will plane the boat off and run fine with no issies as along as I stayed below 3300 rpm, above that, the gearcase intermittent "clunking" starts.
I had a 1960's 40 Johnson Big Twin back in high school in the 70's, that did this same thing, and it ended up locking up the gearcase and ringing off the drive shaft, I had to replace the lower unit. This engine hasn't reached that point yet, and I don't want to run it again until I find out what's wrong.
Here are some things I would like your thoughts on:
The prop spins freely, with no grinding or resistance in neutral,
The motor runs and shifts fine at all speeds below 3300 rpm.
I haven't pulled the gearcase plugs yet, becaise I'm waiting on an impact wrench to break them free.
My question is, if there's water in the gearcase (more water than oil), and I change the seals and add fresh oil, do you think this problem will go away?
I am turning a 15 x 15 Rebel propeller which runs beautifully, but do you think I may have overloaded this gearcase with this wheel?
I know I may be looking at a another lower unit. but any triage you could provide would be appriciated. Obviously, I'd like to try and save this gearcase. The motor runs excellent