225 2001 Optimax W/ stock 120 stats

[majatk]

New to me 2001 225 optimax serial #OT389967
Waiting for smartcraft monitor and cable to arrive and tired of wet sanding and compounding boat so I decided to pull the thermostats out and see if they were clean . They are 120`s dated 9/98 part # 850279-2 , wow never been changed but they were clean . The port side stat was silver but the starboard one on the hose side has a slight bronze tint .

Hope the injectors if were under recall were done . Motor has 500+ hrs

Anyway did I read that along with new 130 stats I need new housings also , under a bulletin

Part#s for mercury stats and gaskets and housings if necessary would be helpful

Thanks

[Savage]

I would run what you have currently on a 500 hour motor, because you wont believe what two Genuine Mercury Marine thermostats and new covers is going to cost you. Test the operation and only replace if necessary.

[majatk]

Was wondering when they did the bulletin years ago and changed to 130`s why was it necessary to change the housings ?

[Savage]

The new covers had a narrowed land to received the new 130* thermostats with a bonded seal. New covers and stats were supposed to pass debris easier while increasing temp in the motor, which reduced plug fouling.

[majatk]

Wondering if I ever do need to replace stats if I`ll be able to get ones that fit these housings or at that point have to change housings .
I have seen how much the merc 130`s cost , haven't seen the housings in a simple search .

I`ve not run this motor , I`ll see if the 120`s work once I install the smart monitor

Guess the theory of passing debris easier didn't pan out to well

[SilverFox579]

Since Smartcraft displayed coolant temp is a "smart average" the best way to determing t-stat function is with a laser thermometer pointed at center of each t-stat housing. Also, the stats only control coolant temp at idle, once the poppet opens they're bypassed.

[JOE54]

really needs to be changed over to 130 system , lots of used parts to be found in parts for sale forum

[majatk]

Yes I understand how poppets work and that stats work at idle

I`m checking the stats in water to see if they open at correct temp now I know I`m stuck with them

Are there even gaskets for 120`s available

I dont know what works correctly on this motor yet , thats why I`m putting a monitor on it

Wonder is if the housings are available still , I know there are parts motor out there . are pro optis the same head as far as the housing surface

Trying not to spend a fortune here this motor has a kind of low #6 ,( so a shop I don't trust says ) haven't rechecked it for myself yet

[JOE54]

same gasket let me know if you cant find any

[EuropeanAM]

Was wondering when they did the bulletin years ago and changed to 130`s why was it necessary to change the housings ?

Slightly different seals and dimension.

The thermostats were changed to 130 degrees in an effort to get the cylinder liners up to temperature and lower the risk of cold seizure (combined with permitting a slightly more consistently-clean running engine).

See Rhonda's post at the top of the Forum: She can set you up with what you need if you decide to go that route.

[majatk]

Thanks everyone , I`ll see how everything works out with this motor . Will change over if it looks to last for awhile .

[squidbefsh22]

Can you get 120 thermostat's anymore. I switched mine to 130's . ordered parts from Rhonda . Was needing to do long needed maint on my '99. Is running great since. Thanks. BC

[squidbefsh22]

Only 120's I saw were Sierra brand and I don't know anything about them. I always use OEM. BC

[JOE54]

120s are NLA

[EuropeanAM]

^^^^ +1

130 Thermostats are the replacement, and where 120's were previously used, replacement covers (or cover kits) were required. Covered years ago in Service Bulletin 2002-08.