I recently bought a 2013 Nitro Z7 from a local individual. The boat is in great shape and had 56.1 hours on it when i bought it. Previous owner said he had only had it out 5 times in the last 2 seasons and it hadn't been started since the end of March (I bought the boat in the middle of August). I was expecting to see ~5500 to 5800 rpms at WOT with a speed of 58 to 61 mph (gps) with water pressure ~7 to 8 psi. When I first had the boat out my top speed was 51 mph with ~5000 rpm at WOT. As the boat was new to me, I did a bit of low rpm running and a bit of idling. While in the lower rpm range, I got an alarm followed by a reduction in power (Guardian Mode I assume). I got the boat out of the water for the day right after. In the next days, I installed a Vessel View to see what i could find out. The next time I took the boat out, the performance was the same. I verified that my rpm gauge was accurate and it was, and also verified water pressure gauge was accurate and it was. In the low rpm range I could watch the temp going over 170, then 180, then 190, closing in on 200 degrees. I shut the motor down at this point. After waiting a few minutes, I started it back up and drove it in the low rpm range. I looked at the temp and was just over 200 degrees and before I shut the motor down I got an alarm. The Vessel View stated it was over heating and to check the starboard thermostat and sensor. I took the boat home and put a new thermostat w/gasket on the starboard side. I also removed the port side thermostat and checked for debris (I've heard about these getting debris caught in them). I also put a new water pump kit in it (impeller direction matched the old), as well as changed the lower unit oil. Took the boat back out with the only intention being to check to see if these parts fixed it...they didn't. I got another alarm, "Overtemp. Stop engine and check for plugged water inlet. Fault code: 521-20: Engine coolant temperature starboard. A temperature sensor value is higher than normal. Took the boat home and pulled the starboard thermostat and it was clean. Then I replaced the port side thermostat and gasket. I then took the poppet valve off and replaced everything with the exception of the spring (it hasn't arrived at the dealer yet) so I put the original spring back on. Took the boat out the other day and still did not see any real differences. I did not get an alarm as i shut the engine down before it began getting hot.
The boat has:
150 Pro XS
24 Tempest 3-blade SS prop
No jack plate (I am expecting a 6" Manual JP to arrive tomorrow)
PTP is ~4" (Motor mounted in the 3rd hole from top)
I am sure the PTP is too much and the prop is too much as well. I will adjust the motor height once the JP has arrived and is installed. I also plan to get the prop re-worked. However, I am concerned about the operating temperature and water PSI. With the overheating issue coming at low rpms, I know the the motor height and prop really shouldn't effect this issue.
Anyone had this problem, or have a suggestion for these issues?
Reply With Quote
