Purchased well maintained 1989 3600 open with 375 3208's. Engines run well and have made some long trips to keys, and savannah ga without any major issues. Just hauled and cleaned gear and did bottom job. Boat seems to cruise easily at 19kts at 2000 rpm would like to cruise above 22kt anyone have experience running this boat at 2300 rpm as cruise speed have read originally cat listed cruise rpm at 2400.
Congratulations on the boat. I am not a 36 owner but will throw my 2 cents in. There is a lot of variables in determining best cruise speed (engine longevity, speed, fuel burn). As you will find reading other posts before locking in on your cruise RPM you need to make sure you are not overloading you engines which will greatly reduce the time before overhaul. I believe the 3208 needs to hit a rated speed of 2800 RPM (WOT under load), ideally between 2800 - 2850 at full gross weight (recommend you verify that number with your Cat dealer). If Cat publishes 2400 as cruising RPM and your props let you get to published rated RPM then have at it. A good prop shop can help you maximize your speed while still achieving rated RPM. From there start measuring your fuel burn numbers so you make informed decisions on how hard to run given the situation. Provided you follow the engine maintenance schedule longevity will not matter much if you operate within those parameters. Hope that helps.
I've got a 94 with the same power. Had several Cat mechanics tell me that a cruise around 2400-2450rpm is just fine for that engine and you will get good life. Depending on fuel and passenger load, that will give me somewhere around 23-24 kts. cruise speed.
The 2400 to 2450 is only fine if the boat reaches the wide open throttle rpm that Cat specified. Otherwise you you overload the engines as the above poster mentioned. Overloading causes overheating which leads to early engine failure.