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Wrong thermostat....

Eric.C

Eric.C

Contributing Member
We have been doing everything we can to maximize our fuel efficiency (FloScan coming soon), and I am not sure if having the 143° t-stats is increasing our fuel consumption. Engine temps hold rock-solid around 145° all day long. I know in a fuel-injected car it can have an effect, but not sure about with carbs. I recently noticed the 143° t-stats are for raw-water-cooled engines. Should I replace them with the recommended 160° t-stats? Or will it not really make a difference?

Thanks in advance!
Eric
 
If you are fresh water cooled, it will help. the newer FI engines typically come with 170 degree stats. (BTW, any gasoline engine will be more efficient with a higher operating temperature, within reason, independent of the fuel delivery method.) You may not notice a huge increase in the fuel economy but the engines will benefit from the small expense.

In terms of economy, if you are serious, you are likely to get a much bigger benefit from redoing the calibration in the carb. It is not very difficult but is very time consuming, especially due to the nature of the marine application.
 
Thanks for the reply. I will probably end up swapping the tstats out then. Any difference is worth it to me. We actually just replaced the quadrabogs this last March, I think it was, with some Holly Marine units. The quadrajets were just too temperamental. It is hard to judge our exact fuel efficiency right now due to the reed switching fuel sending units being far from a good indication of fuel level, but at best guess we are under 1nmpg. It would sure be nice to get better than that. A diesel swap is in our sights for the future, but in the mean time, gotta make the best of what we have. Can't wait to get the GPS FloScans in so we can find our most efficient RPM too.
 
Sorry, Edelbrock...

I know fuel is never going to get cheaper, but we can only hold 140 gallons, and I really want to extend our range more than anything. Even a tenth of a mile per gallon more is a 10% increase or more.
 
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the edelbrocks are a bit easier to tune than the quadrajets but it will still take time.... I think you will find it much more cost effective to spend the time tuning the carbs than to go with the diesel repower....the only real driver for going to a combustion ignition is lack of range with your current propulsion setup (unless you are running offshore charters and make more than 65 trips a year).
 
Being a "new-age" tech, I am still not too familiar with tuning a carb. I figured a new carb would come pretty well tuned out of the box. No? Do you think it would be easier, in the long run, to do the old WOT, shut down, check plugs method of tuning? Or drill and weld a bung for an O2 sensor and monitor that with a DMM while tuning? It would be super easy to get a couple O2 sensors. Most that we replace at my shop just have failed heaters and would still function normally as a stand-alone O2 sensor.

I just can't help but be jealous of my dock neighbor's efficiency. He is diesel in a 32' Sport Fisher and gets anywhere from 1.4-2.0NMPG (depending on speed). I only wish we got that. We took his boat offshore more than ours this last season.

Our speed doesn't seem to matter one bit. Whether trolling at 5-7 knots, or planing at 22 knots, we get about sucks.0 NMPG.
 
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Eric, I presume that these are RWC'd engines (I.E., not fitted with Closed Cooling Systems) ?

It's common to hear a bit of conflicting info regarding 140* -vs- 160* thermostats.
There is no rule that states we must use a 140* stat, unless operating in ocean water since salt begins to crystallize at/near 140*F.
So............., if operating in ocean water, the 143* stats are typically recommended!
Since you are running out of Dana Point, you may want to stay with the 143* stats, IMO.

If your carbureted RWC'd engines were being operated in river/lake water, you could bump this up to a 160* stats with no issues.




.
 
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I just ordered new thermostats for my 1995 454xl complete closed system from ebasic power. They are 170 degree with hole. Right, wrong. or other???
 
kevin_z said:
I just ordered new thermostats for my 1995 454xl complete closed system from ebasic power. They are 170 degree with hole. Right, wrong. or other???
Click to expand...
Kevin...... this is an Apples/Oranges comparison.
Eric's engines are open systems (aka Raw Water Cooled)........ your engines are equipped with a Closed Cooling System.
You can operate in ocean, river or lake water with no issues regarding engine block salt crystallization.



.
 
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STOP! Do NOT put 160 t-stats in a raw water cooled engine or you will cause serious damage.

Here's the REAL reason, and it has nothing to do with 'salt crystals'--that's a long and inaccurate myth.

In a car, the pressure cap raises the boiling point of the coolant from 212 ' F to 250 ' or so. With a R W Cooled engine, there is NO pressure cap, so there is no pressure rise going on. With a 160/ 170 t-stat in there (where it should NOT be) water in the heads can get very close to boiling, especially after you slow down (water flow decreases) after a hard run. This causes the water in the heads to boil, and steam DOES NOT cool worth a damn! The result is serious, expensive overheating with blown head gaskets, cracked heads, blocks, etc.

Don't do it!

Jeff
 
Jeff, I understand the pressure thing and the boiling point of H2O. I suggested a 143* or 160* stat, not a 180* stat.

Also, if salt cystallization is a myth, then why is it that we can find referance to this in some Mercruiser OEM manuals?

This is not Merc, but this suggests that 140* is where the process begins.

WL Holcroft - US Patent 4,133,284, 1979 - Google Patents
... for a marine engine for use in fresh water, the operating temperature can range between 150°
F to 190° F. For an engine for use in salt water, it IS is necessary that the temperature be restricted
to no higher than 140° F since above this temperature salt starts to crystallize and ...

 
No, we are fresh-water cooled. That's why I am asking the question. From my original post:

"I recently noticed the 143° t-stats are for raw-water-cooled engines. Should I replace them with the recommended 160° t-stats?"

The engines obviously run fine with the 143° t-stats, but I am wondering if it is affecting our fuel efficiency as I have heard some people state. We are trying to do everything in our power to maximize our fuel efficiency. If swapping the T-stats to the 160° units the engines call for will make any difference at all, we are going to swap them. If there will be no difference, I won't waste my time.
 
Since you are FWC'ed, i'll omit the comments on the comments regarding RWC'ed...go with the 170 deg stats.

As far as the tuning goes, read the Edelbrock manual...I think the procedure for a marine application could be improved but that's just my view. You have three tuning points of interest for economy improvement. For the most part, max benefit will come efforts directed at the primary side's two systems (3 variables). O2 sensors are possible but they don't tolerate cooling water...I've heard of temporary tuning setups but never have seen one. We used a vacuum gauge, stop watch, and then plug inspection for short term assessment and followed up with Floscan numbers to verify the improvement.

If you think that the carb, straight out of the box, will provide your specific application with maximum economy, please hook me up with your alcohol supplier as you are getting a helluva product!

Two other items to consider for economy - Prop tuning (think PropScan) and teflon (low friction) bottom paint
 
RicardoMarine said:
If the 160* thermostat is recommended, why would you not?
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Because the engines run perfectly fine as they are. Why fix what ain't broke, right? I'm basically trying to figure out if it could just be better for fuel.


makomark said:
If you think that the carb, straight out of the box, will provide your specific application with maximum economy, please hook me up with your alcohol supplier as you are getting a helluva product!
Click to expand...

Home brew! :cool:

As I stated before, I am not all that familiar with carbs. The only carb I have ever really "tuned" was on a 2-smoke dirt bike. I appreciate the recommendations, and I will certainly look into the tuning procedure in the manual.


makomark said:
Two other items to consider for economy - Prop tuning (think PropScan) and teflon (low friction) bottom paint.
Click to expand...

Brother and I have talked about the PropScan before, but we may have to have a serious look into that. As for the teflon bottom paint... is that anti-fouling?? Sounds expensive regardless.
 
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Every "application non-specific" replacement carb will have a general tune provided by its configuration. The OEM carb was set up to ensure adequate performance and to satisfy the warranty needs. The OEM can't control what hull the engine is installed in so they HAVE to jet them on the rich side...the rest short be kinda obvious.

propscan will improve not only the economy but the overall performance. there is at least one other "brand" that performs a similar service...the computer based measurement system is a huge leap over the old block toolset but still requires a qualified technician for a superior end result.

The teflon paints are anti-fouling in the traditional sense...for them to be effective, the hull needs to be used frequently...you need to assess the product you use to the local conditions. When in doubt, ask the Paint Maker's tech service group questions...usually pretty good idea to check for a local user or two of the product and get some first hand feedback....not easy but well worth the effort.
 
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