Help! Water temp too low!

[JimG]

I haven't posted this question, becuase I wanted to put a new sender in, but it did not help...

My water temp barely shows 120 degrees, no matter how I'm running. I've checked the gounds, cleaned the contact surfaces of the old sender, put in a new sender... all to no avail! I ran the boat on the hose this evening for 20 minutes, then backed the sender out to feel the water behind the thermostat. It wasn't very hot, probably 110 degrees or so.

It's a H/M 351W, raw water cooled with a crank mounted Johnson pump dumping straight into a H/M y-pipe where the circ pump would go in a car. I put in a new thermostat, but could the pump pressure be pushing it open against the spring? Once, when it was ice-cold I cracked one of the hoses that run from the thermostat housing to the exhaust manifold. LOTS of water moving there. Shouldn't the thermostat have slowed it down some?

BTW: the boat runs great! No outward problems, good throttle response, no oil consumption, idles very good at 500 rpm. It just bugs me to see the temp so low!

Thanks for your help!

JimG

<small>[ April 12, 2003, 06:04 AM: Message edited by: JimG ]</small>

[MOP]

I think the only thing could be is a bad stat, borrow a push in style meat thermometer put the stat in water and heat it up watch it for its opening temp. it should for raw water cooling open at 160 degrees. I've seen even new ones be off, not very common but worth checking. I have a two cup electric coffee pot that I check them in before installing. The new style gel cap ones are rarely off, but the older spring type get tired and go cooler over time.

Edit thought: I am not sure what that bypass setup looks like but normally the water to the risers is not controlled by the stat it flows fairly free, usually purposely restricted a little by the feeds to insure good flow to the block. If the pump feeds all of its pressure against the stat it can push it open. Love to see a Pic!

<small>[ April 12, 2003, 06:54 AM: Message edited by: M.O.P. ]</small>

[Sam]

M.O.P. explain this new gel style to us.

THX
Sam

[MOP]

The way it was told to me is that inside little brass chamber in the middle of the stat is encapsulated wax that melts at the prescribed temperature it expands pushes the rod and opens the stat. A note if you overheat a late style thermostat replace it that capsule can be damaged.

[MOP]

Went poking around the net found a pretty darn good explanation. Scroll down aways it is explaned pretty good.

http://auto.howstuffworks.com/cooling-system.htm/printable

[JimG]

Tested both thermostats, old and new. Both were fine. Could the water pressure be pushing it open?

[MOP]

It is possible if there is no bypass to the risers.

[JimG]

M.O.P., where would a bypass to the risers be? My t-stat housing has two nipples going to the exhaust manifolds. Maybe that's my problem.. Thanks for your help!

JimG

[harbormaster]

Jim,

TAKE A PICTURE....

POST IT HERE..

[JimG]

I'll do that. Thanks! I'll shoot some pics tomorrow, and post them. Maybe some of those guys with old H/M Fords will respond with how theirs is set up, (BillG, Moody Blu)?

Thanks!

JimG

[BillG]

I do not have a thermostat in my raw water cooled 351. The temp runs at about 80 degrees and I have run two engines for 31 years like that with no problems. The water goes from the crank driven Johnson pump into the block with a "T" and comes out the intake and another "T" into the exhaust manifolds.
Bill G

[JimG]

That's good enough for me, Bill! I'm going to just run the dang thing... and not worry about the temp. I guess too low is better than too high!

Thanks a ton, everyone!

JimG