Engine temp issue

[85Nova2]

I purchased my 85 nova 2 last year, before I take the boat out this year I decided to service everything. I started with thermostats. The starboard side engine gets to 160 at idle and with throttle will go to 200. I bought quicksilver 140 thermostats and installed them the way I installed it in my other boat (other is a 87 196xl) which never goes past 160. I pulled the lower drive and the impeller doesn't look horrible but doesn't look good either. What should I look for? Thank you.

 

[alldodge]

Your saying that you installed a 140 thermostat and it still goes to 200 when throttling up?
Is the drive an Alpha or Bravo? Has the boat been in slat water?

 

[85Nova2]

It's an alpha 1 gen 1. Maybe at some point it was in salt water, boat is 32 years old not sure, but I live in illinois amd bought it in illinois. Yes I bought OEM 140 thermostats from mercruiser.

 

[Bt Doctur]

Always start with a new full pump kit, with just an impeller impeller ,you cant tell by looking at it

 

[tpenfield]

Look for a new impeller kit and a set of manifold/elbow gaskets. You may want to disassemble the riser joint of the exhaust manifold / elbow for inspection to see if the water passages are becoming clogged. Also, if you have any oil coolers in line with the intake hose, check those for any debris that may be clogging them.

Also, what thermostat is supposed to be in those engines? Also, you implied that this is a twin engine boat (?). what does the other engine run at for temp?

What engines are they?

 

[85Nova2]

Always start with a new full pump kit, with just an impeller impeller ,you cant tell by looking at it

I bought a whole kit, waiting to get them, I still haven't re-assembled anything.

 

[85Nova2]

Look for a new impeller kit and a set of manifold/elbow gaskets. You may want to disassemble the riser joint of the exhaust manifold / elbow for inspection to see if the water passages are becoming clogged. Also, if you have any oil coolers in line with the intake hose, check those for any debris that may be clogging them.

Also, what thermostat is supposed to be in those engines? Also, you implied that this is a twin engine boat (?). what does the other engine run at for temp?

What engines are they?

It is twin engine they are 5.7's. I didn't run the port side yet because of the temp issue with the starboard side. All the thermostat kits I've looked at for that year and engine have all been 140.

 

[Bt Doctur]

A 140 stat will give you a bit more time to see and respond to a overheating condition over the160 stat. If you start to see white condensation you might have to use the 160 . Comes from not getting the engine hot enough to burn off any moisture

 

[Oshkosh1]

Your engines should be running somewhere around a VERIFIED 210?. 160? is too low. Most ICE's run at their peak performance/efficiency in a 20? range between 200? and 220? or so. Look at the temp gauge on your modern truck/car. THAT is what you want to see on your boat at speed. Use an IRT to verify the gauge reading at the sender. Add about 10-15? to the shown external temp to get the true water temp(gauge temp)

A T-Stat regulates the lower temp and it's only function is to allow the engine to come up to operating temp quicker. It does not regulate or manage the upper temp. That is a water flow/volume/injection water temp(in raw water cooled boats)

 

[Bt Doctur]

Your engines should be running somewhere around a VERIFIED 210?. 160? is too low. Most ICE's run at their peak performance/efficiency in a 20? range between 200? and 220? or so. Look at the temp gauge on your modern truck/car. THAT is what you want to see on your boat at speed. Use an IRT to verify the gauge reading at the sender. Add about 10-15? to the shown external temp to get the true water temp(gauge temp)

A T-Stat regulates the lower temp and it's only function is to allow the engine to come up to operating temp quicker. It does not regulate or manage the upper temp. That is a water flow/volume/injection water temp(in raw water cooled boats)

Think again, NEVER that high in a boat even with fresh water cooling.Might try reading the manual for your engine

 

[tpenfield]

Your engines should be running somewhere around a VERIFIED 210?. 160? is too low. Most ICE's run at their peak performance/efficiency in a 20? range between 200? and 220? or so. Look at the temp gauge on your modern truck/car. THAT is what you want to see on your boat at speed. Use an IRT to verify the gauge reading at the sender. Add about 10-15? to the shown external temp to get the true water temp(gauge temp)

A T-Stat regulates the lower temp and it's only function is to allow the engine to come up to operating temp quicker. It does not regulate or manage the upper temp. That is a water flow/volume/injection water temp(in raw water cooled boats)

Not sure where you would be getting that information . . . but . . . in an open cooling system 210 would be right around the boiling point of water so the engine 's cooling system would essentially be boiling over. A closed cooling system could tolerate temps that high, based on pressure/temperature relationships, but still would be considered too hot.

 

[2fishy4u]

Yeah, my car runs at 210. My boat runs at 160. It has gone up to 210 before, and I paid the price with a new headgasket. 2 different worlds I think

 

[Oshkosh1]

Yep. You guys are correct.

Marine blocks should run much cooler.

Too much time thinking auto/truck heads.

I was just out today and my water temp never got over 140...even running at close to WOT. Injection temp was about 65deg. The block was about 30deg hotter but I never saw over 175deg on the IRT.

Auto heads use heat tabs which melt at 260, Diesels melt at 230 and Marine head tabs melt at 195.

Disregard my previous blather regarding the temps...