Thermostat in Florida

[sam03v]

I live in north FL. I have a 35hp johnson 1978 seahorse. Recently I was advised by a local shop to leave the tstat out since the water around here is warm to begin with and the risk from sand blocking passage ways in the powerhead out wiegh the problems of not having a tstat.

Does anyone wish to comment on this advice?

thanks in advance

 

[Paul Moir]

Re: Thermostat in Florida

You may remove it without affecting the engine if you run in water that is 140 degrees F.

 

[emdsapmgr]

Re: Thermostat in Florida

If you run the engine in sand, you will have more problems with the deterioration of the rubber impeller than the thermostat. Thermostats provide water restrictions to insure that the water fully fills the head cavities, distributing cooling water evenly to all parts of the block. Cold running engines have other driveability, combustion and wear issues. Run the thermostats.

 

[Texasmark]

Re: Thermostat in Florida

Gotta agree with emd. I ran older engines without them (before they used them). I had a '75 70 hp that the stat cost me an OH. ($1000). Bought it used and that was before alarms.

Current engine stat stuck shortly after purchase so I chunked it...had overtemp alarms on this engine d .

Was running in cooler water and only 3 cyl engine didn't idle very well and after reading several comments on here bought a new one and installed it. Glad I did, especially with my clutch rattle thing.

I think if you, Sam, change it every year or two you won't have siezure problems.

Water pickups are in front of the prop; not behind it like the old 50's and 60's OMC smaller engines (bad bad designed lower unit. :devil: .

Unless you do a lot of backing up I wouldn't be worried about sand and agree on wearing out the impeller; as a matter of fact, changing both every couple of years would probably be your best bet. My 2c.

My engines stat is stamped that it starts opening at 120F that puts it fully open at the 140 that Paul mentioned.

Mark

 

[sam03v]

Re: Thermostat in Florida

Thanks for your replys. I'll be stopping by the Johnson dealership after work today.

I recently rebuilt this motor(1st time adventure for me) and haven't even broken it in yet, so I was really surprised when the shop owner told me not to worry about the thermostat.

thanks again...

 

[Joe Reeves]

Re: Thermostat in Florida

(Thermostat Purpose)
(J. Reeves)

Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperture to compensate for the distortion.

With the thermostat removed, the difference in temperture between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

The thermostat in your car isn't there simply to have the heater function properly..... think about it.

 

[Texasmark]

Re: Thermostat in Florida

There is truth to what Joe says (my free opinion, of course). For years, Merc advertised "cam turned pistons" which were supposed to do just what he said; fit the cylinders as they got hot.

My 2c,

Mark

 

[sam03v]

Re: Thermostat in Florida

Been awhile since I looked at this thread. Now I remember the reason I left the t-stat out in the first place. The new thermostat kit came with a spring that didn't fit inside the water cover of my motor. Even when fully compressed I couldn't bolt the water cover onto the head. I told the shop owner about it and thats when he said to leave it out. I looked at the parts manual and there should be a spring, but there is no way that spring would work. I think someone put a different water cover on the head of this motor. Any way I double checked it and the cover will hold the t-stat in place(without the spring) and still allow it to open. Does this sound familiar to anyone?

 

[F_R]

Re: Thermostat in Florida

The spring needs to be in there. But the Correct spring. It allows pressure relief to bypass the thermostat under certain conditions.

 

[sam03v]

Re: Thermostat in Florida

The spring needs to be in there. But the Correct spring. It allows pressure relief to bypass the thermostat under certain conditions.

Okay,I think I see, if the water pressure gets too high the entire thermostat will lift off the head compressing the spring which allows more water to flow? Is that correct? I found a head assembly on ebay that includes the water cover for $40 (including shipping) that appears to have the larger space for the spring. Even if I did have a different spring I don't think it would work with the current water cover that is on the head of this motor.

 

[F_R]

Re: Thermostat in Florida

Correct

 

[funpilot]

Re: Thermostat in Florida

sam,

I think it is more like, the thermostat gets blocked or stuck, and the water pressure builds up and overcomes the spring and allows water to flow into the block. You will probably get an overheat alarm, and in newer motors limp mode, but you would get home without destroying your motor. After an overheat I would look at water inlets and then cleaning and checking the function of the t-stat. Incidently, the last time I rebuilt an outboard, I did just that. They both opened at 143 Degree F. Don't tell anyone, but I reused them.

You can go to NAPA and get a nice catalog that will specify the exact spring and T-stat part numbers for your motor. They use the same numbering system as Siera. You can also call iboats and someone could help you order the right parts to fit your ebay housing.

warmly,
funpilot

 

[Jquest]

Re: Thermostat in Florida

Silly post on my part. Didn't notice the date.

 

[F_R]

Re: Thermostat in Florida

They advertised the motors as having "thermostat and pressure controlled cooling system". That's the pressure controlled part. Stuck thermostat got nothing to do with it.

 

[Texasmark]

Re: Thermostat in Florida

The stat is for low speeds and the bypass for high engine rpm's or high ram (water) pressure from the lower unit moving thru the water. The bypass area is 4+ times that of the stat and allows more water through the powerhead when needed.

Mark

 

[sam03v]

Re: Thermostat in Florida

The stat is for low speeds and the bypass for high engine rpm's or high ram (water) pressure from the lower unit moving thru the water. The bypass area is 4+ times that of the stat and allows more water through the powerhead when needed.

Mark

Here's comes the dumb question....Would the motor overheat if the t-stat doesn't lift off under high pressure?