overheat problem

[craisim]

I have a good running 85' 150GT with an overheat problem. I have been trying to find the reason that the right side overheats. I have one temp gauge and it is connected to the right side head. As summer approaches, the motor runs hotter and hotter. I cannot get above about 4000 rpm without the gauge getting into the red with a warning horn activation.
Here's what I have done so far;

1. removed and replaced the water pump assembly and checked timing-ok.
2. pulled the head and sandblasted the water passageways.
3. changed the thermostats and poppet valves. (I even ran without a thermostat.
4. inspected the engine block, rubber flow deflectors are in place, all passageways are open and clean. Inspected under the exhaust cover-all clean.
5. checked the indication system. Horn and temp indicator agree. Indicator works well on the other head.
6. at about 5000 rpm, water pressure is 15psi.
7. I am at the end of my rope, any ideas?

[RUSTY63]

Welcome to the BBC.

I have a question, besides using the guage.... have you checked the cylinder head temp with any other devise?

Is the horn solid until the motor is turned off or does it go away when you slow down?

[craisim]

No, I have not used any other devices to measure temp. The horn sounds steady and I must shut the engine down and wait a few minutes before it stays off when I turn the ignition key on. The horn sounds when the temp gauge gets into the red. I can also tell by the feel of the two heads that the right side is considerably hotter than the left when running. I remember that I do have a little spray of water coming out between the lower housing and the lower unit when I run on the muffs. I disregarded this since I have good water pressure (15psi). Thanks alot.

craisim

[RUSTY63]

Have you ever had a water pump impeller come apart on this motor?

I mean come apart like parts missing?

[craisim]

No, not that I am aware of. I replaced the impeller and housing when I first experienced this problem. I think I bought the boat with problem. The horn did not work and the temp sensor was on the other head. As soon as I replaced the horn, it started going off when the water got warm. I switched the sensor to the right head and sure enough, it showed that the head was indeed overheating, thats when I started my maint. actions. Thanx

craisim

[ChampioNman]

I would pull the exhaust housing off AND also pull the heads off, just to check the H20 deflectors shape on both sides. Check out and replace the T-stats with the new upgraded ones poppit valves etc.CM

[craisim]

OK. I already have the exhaust cover off. all clean. the water flow diverters in the right side head look fine to me. They are in place and still pliable. I have already put new t-stats and poppets in with no effect. I will continue to look and putter around. If you all have any other ideas please let me know. If I come up with anything, I will let you all know. thanks much.

Craisim

[RUSTY63]

I will look at some stuff tomorrow and see if I can come up with any more ideas.

[jglenn]

have you pulled the right side themoststat after running it on Muffs to see if there is any water present?

[Ricardo Paragon]

I have found the same problem a long time ago, and was the adapter plate under the powerhead, was corroted on side, plugged with salt and didn't let enough water get in one side of the engine and was ok in the other side.

A good test is run the engine, with propeler test, without termostat cover and see if the amout of water are the same on both termostat holes, before try to take the PH off.

Good luck,

RICARDO!

[craisim]

No, I will try that tomorrow and get back with you all. thanks for the help.

craisim