Need help stumped...
 

My engine will not get above 110 degrees in water @ idle. On the hose it warms up perfectly normal and will idle at 140 all day. Absolutely no problems last year. If I take it out and run it it will get to normal temp but as soon as get off plane and back to idle in no wake zone, Temp drops back down to 110 and it loads up on fuel. With the long slow zones this is a problem!

I did put a new sea pump on when I got it ready this spring. Thermostat is same one as last year 140 high flow from Hardin marine. New plugs. No carb changes. fresh fuel. I'm using a crossover set up with bypass to thermo housing. None of this has been changed from last year.

I have 4psi of water pressure @ 800rpm
10psi @ 1000 and 20psi anything above 2000. this is all at dock not even moving. Could water pressure have anything to do with this. Is it possible the themo is stuck open? i just checked this in a suace pan on stove opening and closing fine at correct temp. I've taken it out a can see a very little bit of light through it. obviously the bypass Is it possible my water pressure are too high causing more flow??

Any ideas? I got to get this thing fixed before my memorial day vacation or i'll be boatless and very unhappy. Thanks for any input.

Try running a higher temp stat. Check your gauge for accuracy also. It's still early yet so water temp in the rivers, lakes bay etc is still a bit on the cool side. Running at speeds the stat should be open by then and things are normal as you say. So the problem at idle speeds is the stat is opening too early not allowing the eng to get to temp. Guess that new pump work huh?

I also don't don't think you will get 140 degrees WT at idle with 60-75 degree water even with the thermostats closed. We don't run thermostats today, but I don't think we got much WT at idle when we did. I also don't see the link between the WT and the AFR at idle.

check to see if you stat is closing.

You shouldn't see any light thru a closed therm. It's not closing all of the way. We see that all of the time in autos, now that the computer monitors warm up time and temps. Too cheap to stress over. Change it. I also agree w Ben. I don't think 30 degrees will be your loading up answer. I have been wanting to add a wp gauge to my 7.4. Where is your sender located?

I check thermostat in a pan on stove it defintely opens and closes at correct temp. The light through thermostat is the bypass. Some have a hole drilled in them . the Hardin Marine is set up a little different. i thought the high WP maybe flowing too much water through block. Last year the engine at least got to 120 with same bay water temp.
I too am thinkin it maybe a carb issue. I clean the idle mixture screws and reset. I just dont understand why when on hose with less WP it idles fine at 140.
Thanks for the input so far.

My gauge taps in at intake by thermostat. I wuldnt think loading up at idle would be from the 30 degree temp either. yesterday i ttried 2 hoses into sea strainer WP was @ 4 psi. engine temp drops to 100 and loads up. remove one hose so WP just above 0. engine warms to 130 and idles fine.

Changing thermostat to be sure. starting to think carb issue.
thanks

Heats up more on the hose because your not getting nearly the same amount of water out of the hose and probly not as cool as lake/river water either. I would never run my engines up to anything above idle on the hose except for short taps on the throttles. I'd still try the higher stat.

So i think I was off on this. I know think its a water reversion problem. Let the engine load up, stoppped and pulled plugs. water on plugs. after idling for a bit the rpms will eventually drop t0 600 at idle only causing it to get worse. Guess Ill start a new thread. thanks