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Hello, I recently ran my boat on muffs in from of my house, I verified they were on correct and that the lower unit was down. It seemed to climb in temp pretty quickly it hit 158 degrees in a few minutes, anyone out there know if this is normal? I’ve never seen the temp that high to my knowledge.
Thanks in advance,

158 doesn't seem that high, depending on the motor it probably has a 140 or 160 degrees thermostat. I know on some drives there is a drain hole you have to cover with duct tape to keep more water flowing through

If it regularly runs too much cooler than that, you may have a sticking thermostat or a gauge issue

On the water I have never noticed it get higher than 140 I don’t think it seems to run really cool. I’ll try it out tomorrow and report back I guess I was more worried about having hurt the water pump or something like that when running the muffs on it.

140 isn’t even up to operating temp and will cause poor economy. 160* thermostat is pretty much standard on marine engines now, so 170 is perfectly fine. 140 used to be the standard and they switched to the 160 back in the mid 80s. What engine do you have?

Pretty sure mine runs just shy of 170 in all conditions.

The engine is a Mercruiser 300HP 6.2 liter. 2017 220s is the boat

Jrader638 wrote: Fri Jul 24, 2020 6:26 pm Hello, I recently ran my boat on muffs in from of my house, I verified they were on correct and that the lower unit was down. It seemed to climb in temp pretty quickly it hit 158 degrees in a few minutes, anyone out there know if this is normal? I’ve never seen the temp that high to my knowledge.
Thanks in advance,

As Lake water temperature plays a role in cooling systems it can attribute to higher or lower temps. Closed cooling not as much but it can be noticeable.

My open systems ran cooler in 65 deg water vs 85 degrees.
No worries.. boat on

FWIW, my 2018 R5 with a 6.2 l VP380 runs mostly at 160-162 degrees.

Was out yesterday and watch closely because of this thread. Mine ran at 170 idling or cruising, and went up to 172-173 when I did short WOT runs. Water temp is high 80s, and my cooling system was fully serviced this spring.

My previous boat had a Merc B3 350 Mag that would do the same in the driveway, I think it was an issue with the muffs and hose not getting enough water to the engine. Never had any issues in the open water, but I'd get that in the driveway as well.

I have an 2017 R3 with 300HP V8 Volvo Penta DP. During 20-30 minute cruises it tops out at high 190's to just over 200 degrees. When I shut it down it normalizes to 150/160. Should it be climbing in temp during these cruises to 190-200? Serviced annually at dealer. Impeller changed every year.

My 300 runs at 162. After a wot run I might see 170 but never for more than90 seconds. I am now boating in 88 degree water so I’ll check to see if that makes a difference. As a reference it was hard to get the engine to 160 on miffs with cold mn water. Think 50 degrees from the hose

akorcovelos wrote: Sat Jul 25, 2020 10:12 am 140 isn’t even up to operating temp and will cause poor economy. 160* thermostat is pretty much standard on marine engines now, so 170 is perfectly fine. 140 used to be the standard and they switched to the 160 back in the mid 80s. What engine do you have?

My 2017 Mercruiser 350HP 6.2L uses a 140°F thermostat. That's also what it runs at on the water. Basically...same engine as the OP

160°F is right on the edge of when salt will deposit in the engine when running in salt water. That's why they still run 140s.

People with newer Volvos have closed cooling so everyone that posts with newer Volvo temps..they don't apply.