7.4 Liter Merc Operating Temp

E

emlevins

New Member
Sep 27, 2009
77
Lake Erie
Boat Info
2000 260DA
Engines
7.4 w/Bravo III
I have a 2000 260DA with a 7.4 liter Merc. What is the normal operating temp for this model year engine?

I am running 170 degree when warmed up at idle and up to 190 or 195 degrees at 4K rpm or so. This is consistent..

Thanks.
 
Mine operate at 165 and never under normal operation go above 170. 195 is on the warm side I think. Sounds like a new impeller is in your future, when was the last time it was changed. But that increase in temp is an early warning that it's going I would bet...

Or could be a stuck thermostat that is not opening enough. If the T-stat is easy to get at might want to look at that first as I would bet that is a cheaper fix.

Take Care!
 
Last edited:
are you reading the analog temp gauge? If so its probably wrong. If you had someone with a scan tool you would know for sure what its reading. I see allot of boats with the analog temp gauge always read high.
 
My port 7.4 was reading around 195 this weekend. The raw water pumps are new. Cleaned out the transmission cooler, oil cooler, fuel cooler, and heat exchanger on both engines. Same results. Connected the scan tool and both run about 165. I'm good with that. Also both tachs are exactly on the money. :smt001

Having a scan tool is good. Next weekend I'll put an ohm meter on the sensor and see if it's off or the gauge is wrong.

Best regards,
Frank
 
mwph said:
My 98 warms up to 170 & never gets above 175. I'm no expert but 195 sounds awfully warm. On a side note...How long do you run @ "4K rpm or so"?
Click to expand...

I'm not running 4K for long - but the temp clearly increases when running hard and decreases when at lower rpms.

Don't know when the impeller was replaced since I've only had the boat for 2 months.

My mechanic tells me the engine temp is in the range.

So it is possible that it is the gauge reading high?

I'd like to try and get through the season and then have work - if it needs to be done - done over the winter....

Thanks for the replies.
 
My port engine runs around 160 and the starboard runs around 175, but I cruise at about 3,000 - 3,200 rpm. I think the fact that the starboard engine circulates water through the water heater might have some bearing on mine.
 
Mine runs about 175-ish on my analog gauge. I run at about 25-30 MPH on most days which is about 3000-3200 RPM.
 
emlevins said:
I'm not running 4K for long - but the temp clearly increases when running hard and decreases when at lower rpms.

Don't know when the impeller was replaced since I've only had the boat for 2 months.

My mechanic tells me the engine temp is in the range.

So it is possible that it is the gauge reading high?

I'd like to try and get through the season and then have work - if it needs to be done - done over the winter....

Thanks for the replies.
Click to expand...

Well if you are going to wait you will want to know for sure what the temps are. Based on FC3's response the gauges could be wrong.

Here is a cheap IF gun for piece of mind...

http://www.harborfreight.com/review/product/list/id/3503/#customer-reviews
 
Since your temp gauge goes up and down tells me the engine is heating up and cooling down with load demand, regardless weather the gauge is calibrated or not.

Your water temp issues are a sign of a water temperature not being regulated consistently, water pump not keeping up with the engines demand or too much demand on cooling system.

I would check your belt first. Then the thermostat and move to the water pump. You don’t want to go down the last road. I wouldn’t wait till the engine starts running hotter to get your mechanics attention!

My 7.4 warms up to 145* and does not move from there. This weekend I made two 1 hr runs turning 3200 - 4200 rpms and my water temp did not move from 145. ... Last year after 1/2 hr of upper rpm running my water temp would creep up some, not as high as yours. ... Water pump in my Alpha drive was starting to go south with warn end seals.
 
Last edited:
You must log in or register to reply here.

Forum statistics

Threads
113,247
Messages
1,429,248
Members
61,127
Latest member
Ants84245srv
Back
Top