Temperature Question!!

[hg849]

my M, ercruiser 305 5.0L runs at about 140 degrees while at 2800 RPMs , When i take it up to 3500 RPMs the temp starts to rise to 165-175 degrees ......IS THIS NORMAL OPERATING TEMPERATURE AT FOR THIS ENGINE???

it is carbs and RWC

 

[Bondo]

Re: Temperature Question!!

Ayuh,.... It seems to be climbin',... How old is the Impeller,..??

saltwater runnin' I assume,..??

 

[cr2k]

Re: Temperature Question!!

If your impeller is 2 years old or older it should be replaced. What you describe is one of the first signs of needing attention.
If it's been recently replaced check your manifolds, they may be getting plugged with rust/scale.

 

[hg849]

Re: Temperature Question!!

i dont know the age of the impeller , just got this boat. n yes guys saltwater operation . i read some threads where others operate between 160-180 cuz the thermostat wont open till 160 any feedback??????????

 

[Bondo]

Re: Temperature Question!!

Ayuh,.... saltwater, raw water cooled should have 140? T-stats...

 

[paultjohnson]

Re: Temperature Question!!

My 86 4.3 has a 143 deg stat in it. It doesnt matter if the water temp is 50 deg or 80 deg, WOT or at idle, the temp gauge stays in the low 140s. [ once I get it to operating temp or course ]

 

[ENSIGN]

Re: Temperature Question!!

Since you just got the boat and don't know about the impeller I would suggest replacing it. It's cheap insurance.

 

[tpenfield]

Re: Temperature Question!!

my M, ercruiser 305 5.0L runs at about 140 degrees while at 2800 RPMs , When i take it up to 3500 RPMs the temp starts to rise to 165-175 degrees ......IS THIS NORMAL OPERATING TEMPERATURE AT FOR THIS ENGINE???

it is carbs and RWC

I had a similar problem that developed last year on my mercruiser. It turned out to be related to some marine growth that worked its way up the out drive inlet and became lodged in the narrower passage tube leading to the transom assembly.

At lower speeds/rpm it maintained temp and then at cruising speeds it went up into the 175 range. It took a while to find it as I checked a lot more 'obvious' stuff first.

 

[hg849]

Re: Temperature Question!!

yeah but the factory specs says thermostat opens at 160 .......thanks but i cruise at 2800-3000 n it does fine there the problem is when i go past 3100 rpms n start picking up speed

 

[Bondo]

Re: Temperature Question!!

yeah but the factory specs says thermostat opens at 160 .......thanks but i cruise at 2800-3000 n it does fine there the problem is when i go past 3100 rpms n start picking up speed

Ayuh,.... 160? is Not for Saltwater, but freshwater run....

Yer gettin' overheat, at higher loads.... pretty normal for a Bad impeller, or clogged risers....

 

[achris]

Re: Temperature Question!!

Since you just got the boat and don't know about the impeller I would suggest replacing it. It's cheap insurance.

I'd suggest a FULL service... As you have no knowledge of the service history, assume nothing. Service the drive (Water pump, oil change, grease the unis), engine service (New spark plugs, oil and filter, fuel filter, ignition system checks, timing, carb adjustments) AND GREASE THE COUPLER!!! especially if you'll be doing a lot of low engine speed work .... (I'm a bad ***** cat... )

For any futher advice we need to know the year of the engine/drive (this may or may not be the same as the boat).. Serial numbers are better. Look for 3 different (but similar) numbers. Will be either 7 digits, or a '0', then a letter, then 6 digits.... One on the engine, one on the drive, one on the transom assembly. With those 3 numbers you'll be able to get anything you need for the engine/drive.... (post up the numbers and I'll give you a link to the manuals you'll need...)

Chris....

 

[hg849]

Re: Temperature Question!!

I'd suggest a FULL service... As you have no knowledge of the service history, assume nothing. Service the drive (Water pump, oil change, grease the unis), engine service (New spark plugs, oil and filter, fuel filter, ignition system checks, timing, carb adjustments) AND GREASE THE COUPLER!!! especially if you'll be doing a lot of low engine speed work .... (I'm a bad ***** cat... )

For any futher advice we need to know the year of the engine/drive (this may or may not be the same as the boat).. Serial numbers are better. Look for 3 different (but similar) numbers. Will be either 7 digits, or a '0', then a letter, then 6 digits.... One on the engine, one on the drive, one on the transom assembly. With those 3 numbers you'll be able to get anything you need for the engine/drive.... (post up the numbers and I'll give you a link to the manuals you'll need...)

Chris....

I don't know the year of the engine the serial number is not visible the outdrive is a SE116 installed brand new in 2009.

 

[hg849]

Re: Temperature Question!!

Ayuh,.... 160? is Not for Saltwater, but freshwater run....

Yer gettin' overheat, at higher loads.... pretty normal for a Bad impeller, or clogged risers....

Manual says 160 for RWC and FWC

 

[Friscoboater]

Re: Temperature Question!!

I am on my second boat and both ( one was a brand new 350, and the other is a 454) and both in 110 degree weather and 98 degree water temp, run right at 170 degrees. In the early season or late season when the water temp was in the 80s, they both ran much cooler.

 

[Don S]

Re: Temperature Question!!

I don't know the year of the engine the serial number is not visible the outdrive is a SE116 installed brand new in 2009.

If you plan on getting any real help with a question, you are going to have to come up with some information. There is a tag on the back of the block just above the starter that has the Mercruiser serial number on. A digital camera and a trouble light usually gets the info within a few shots, even if you can't see in there.
A year of your boat would help give us a rough idea. Right now we don't know if you are talking about a 1977 or a 2007 engine.

 

[ktbarrentine]

Re: Temperature Question!!

Manual says 160 for RWC and FWC

Hmmm... which manual? Really need the year manuf of the engine. My 1990 5.0L MCM (mercruiser service manual #15) only specifies 143 for the T-stat. Sounds like you have a 143 t-stat and the basic prob is not enough water flow at the higher rpms. (I'm still very new at this and am learning a great deal from these threads). I actually had the opposite prob that was related to an old impeller. Temps rose during low rpm in no-wake zones, and then came back down at higher rpms when I got more flow from the degraded impeller.

 

[achris]

Re: Temperature Question!!

I don't know the year of the engine the serial number is not visible the outdrive is a SE116 installed brand new in 2009.

That helps a little ...... SE116 is a Gen II, so we know it's 1991 or later. (that's still a 20 year span!)...

 

[hg849]

Re: Temperature Question!!

That helps a little ...... SE116 is a Gen II, so we know it's 1991 or later. (that's still a 20 year span!)...

actually it was purchased brand new in 2009

 

[achris]

Re: Temperature Question!!

actually it was purchased brand new in 2009

SE116 is an SEI drive, not Mercruiser factory. That drive was installed to REPLACE the original. The fact that the SEI drive was new in 2009 doesn't make the engine 2009.... From that drive all we now know is that the ORIGINAL drive was an Alpha One Gen II, produced from 1991 and later...

Have you looked at the engine block just above the starter motor, like Don asked?

 

[hg849]

Re: Temperature Question!!

there was a paper sticker there but it got erased is that wat u guys r talking about ? based on the casting number the block is from 76-80ish