salt water and thermostats

[JP BRESCIA]

I was reading the results of a search I did on thermostats and came away with a few questions. According to a board member, salt water will start to "crystalize" above 160 degrees. It also appears that Mercruiser started using 160 degree thermos in the late 90's up from 140 degree thermos prior. Why would they do that?

I recently purchased a 1999 fresh water classic(502MPI) and it runs 160-170 degrees. My 18 classic ran in the 140-150 range so I keep looking over at the temp guage with concern, especially since I run 1/2 the time in salt water. It was bothering me enough that I just replaced the fresh pump and thermo in the new boat and opted for 140 thermo.
Now I am dealing with the fact that the factory put in the 160 thermo for a reason. I am a little concerned that it has something due to the MPI engine and I should go back to the 160 degree. :confused: Any help is appreciated. BIGGRIZZ are you out there ?????

I think BIGGRIZZ was a thermo guy with Mercrusier or something like that

[gcarter]

Have you considered a heat exchanger?
I'm still a little puzzeled why so many on this site are so hesitant on going this route?
They've never been cheaper. And it seems it would make winterizing so much easier for you Northern guys. :yes:

[Bad-Tat]

The Grizz will probably tell you to put a closed system on it. He has them on both boats.
I put one on Bad-Tat and it runs at 175-180.

[Donzigo]

George, I'm almost convinced to change mine to FWC. I've hd it before and it's great.

I'd put the 160 thermo back in the boat. A cold engine is not good.

[GeneD]

Fuel injected engines need the added heat (with a higher thermo than carburated engines) in order to run properly.

[MOP]

There has been a lot of debate on thermostat temps, like stated 140 and now 160 for Merc. As best I can remember OMC ran 160 for many years, that I will have to check back through the manuals. The problem is salt water when heated over a certain point crystallizes forming deposits. I know a few guys that run high temp T stats but flush well after use and do not seem to have a problem, I myself have run 160 in all my stuff which lets the engine run 165-170 and have never had any problem. Running cool T stats robs some performance and may cause more engine wear not letting the engine come up to proper tolerances. Like GC says closed cooling is the best way to go, systems can be expensive or shopped used to save a few bucks. I picked up a two year old cooler for $50 just asking who had what kicking around, if you go used have it cleaned and pressure checked at you local radiator shop make sure the seller will take it back if N/G.

Phil

[gcarter]

I just reread this thread. I happened to remember the last time I shopped for a HE was in about 1990 and the price was about $700.00.
Now I just ran this through the inflation calculator and that comes out to about $990.00, hence, I don't think they've ever been cheaper.
I got mine (San Juan full system, including shipping and tax) for just over $600.00. That kit includes everything you need, except anti-freeze! LOL :smash:

[gcarter]

Ding Ding :)

Thank you Dr. Drago :D :D
Gosh darnit Scott, your right....I should have stated the obvious in #2. Let me try again;
Not only would a HE eliminate salt from your engine, butthey also include a 180* or higher t=stat, thereby maintaining a higher engine temp.

[MOP]

I wonder what the reasoning is behind the 140 on the later Merc models, heat makes power fuel injected or carbed. Automotive temps are now in the 190+ range, which gives greater efficiency and more power. I am pretty sure Big Griz said the extra power he gained by going to closed cooling (ie: higher temp) more than made up for the +or- 50 extra pounds of hardware.

[MOP]

I thought he said he made a bit more power that is was worth the switch, only he can answer that one.

[JP BRESCIA]

Based on the responses, I should have kept the 160 Thermo which made me run 170-175 degrees b/c of greater power and better efficiency. However... my GPS disagrees. I recently tested the difference in top speed with the thermo's. With the 160 thermo...approx 10 gallons of fuel...tabs up... I ran 70.5 MPH at 175 degrees. With the 140 Thermo..approx 10 gallons..tabs up.. I ran 71.2 at 150 degrees.. :confused: :confused:

I trimmed the boat what I felt was the same but still possible that I may have been trimmed slightly better with the 140 Thermo or something like that that is the cause for the discrepency. I am not sure if the fuel heater has anything to do with my issue or not but, due to the salt factor, I plan to run the 140 Thermo for peace of mind. Simply not enough difference to sway me towards the 160 thermo. :spongebob

[JP BRESCIA]

And one more thing.....
SANTA...I have been a good boy this week and hope that a closed cooling system fits in my stocking..... :smash: :cartman: