120hp Johnson Outboard??

greateastern · #1 07-06-2010, 11:44 AM

I long since sold my V-20, but still remmeber all the great advice I received from this web site. I now have a simple 1750 Vector Hydro Sport which has been very good to me, I was wondering on my 1998 120hp outboard do you really need to run thermo-stats? Seems now that the bay temp has hit 80 degress the engine runs on the warm side, when your up on plane it is just about in the white zone the danger zone. No alarms or beeps are going off... but i'm just wondering why the thermo-stats? The cooless water temp. the outboard runs in is about 60-50 degrees in the fall. I'm just so tempted to pull these stats out.

Hope you can help.

Skools Out · #2 07-06-2010, 01:14 PM

i ran the sister motor a 140 with no stats it ran fine just it ran rich in colder temps. you could buy lower temp t-stats. they made 2 different motors some went north to dealers that had higher temp stats than those of the southern motors. you may have the wrong set for your water temps.

tsubaki · #3 07-06-2010, 02:03 PM

Pay attention to what Skools is saying.
Most of the time the only discernible difference with or without t-stats would be the initial warm up and when trolling for long durations.
Me, I'd put them in to rule out other problems that might arise later.

THEFERMANATOR · #4 07-06-2010, 02:52 PM

First things first, what is the model number on the engine? According to the catalogs they didn't make a 120HP in 98. If it is a late model V-4 90 degree looper then I would suggest checking the water pump first as that system uses water pressure to bypass the stats at upper RPM's. Weak impeller will make the engine run right at the redline for temp when under power. And if it was mine, I would leave the stats in it. Even down here in Floridas warm water I lost an engine from carbon build-up due to no stats. Loopers need alot of engine heat at idle in order to burn the fuel and not carbon up really bad. Figure out exactly what engine you have first, and then make sure the cooling system is working like it is supposed to. It could just be some salt build up on the stats that isn't letting them pop off there seats under pressure causing it.

phatdaddy · #5 07-06-2010, 06:39 PM

all good advice above, i would add just one thing, test your t-stats and verify at what temp they are operating. i've tested brand new ones and had them not open at the suggested temp or open at two temps 20-30 degrees apart from each other.

greateastern · #6 07-07-2010, 06:44 AM

Ok, I knew I could count on you guys, it is a 1990 not a 98. and Yes, I have have installed a new water pump, and yes I have put the stats in water to check operation temps.(I feel that they open way to late 180-190 degrees) I have even changed the sending unit to make sure of all things. Next I'm going to go with a new gauge no more colores I need numbers) To me the stats open up way to late, I heard about the stats that where mentioned, that they use down south asked my local supplier and he said that he has never heard of it. The stats I have in are white in color I read about a black colored stat that runs cooler??? any thoughts on part number??

Also I bought new stats and the motor overheated in the drive way with the garden hose. Put the old ones back in and it is fine. Just in the bay, running up on plane (4000 rpm) she runs to hot for my comfort.

Thanks,

Skools Out · #7 07-07-2010, 06:59 AM

yeah i run the black ones as they do run cooler you can open the black ones and clean them plus you can gut the black ones then they will still hold back water and make the motor run around 170* when gutted. i'll see if i can find the part number on the black set for ya.

Skools Out · #8 07-07-2010, 07:02 AM

hey just a thought does your t-stat cover housings have water hoses off them or are they solid covers? the type with tubes are what Ferm was talking about the bypass system the solid covers don't open bypass at higher rpms

greateastern · #9 07-07-2010, 07:50 AM

they have hoses on them, i do not understand the bypass system. But ferm seemed to get it right, higher rpms motor runs hotter lower rpms motor runs cooler. One would think water pump but pump is new. Just called supplier again they do not know of any other stat but the white one. I' tempted to just pull them out for the summer and put them back in, in the fall.

Skools Out · #10 07-07-2010, 02:27 PM

take the diverter valve apart and clean it on the bypass system it may be stopped up or make sure it works without the motor running move the throttle level wot then look on the side at the bypass valve make sure it is moving.