1992 V6 225-HP: Cooling System

[jimh]

I have an Evinrude 1992 E225TXNR outboard. I have replaced the rectifier/regulator and the power pack. I notice that the upper cylinders run noticeably warmer than the lower ones. These observations make me wonder if there is a bit of a cooling problem with the upper cylinders. Perhaps the problems with the electrical components were caused by overheating.

Are there any retro-fits or modifications recommended for these engines to enhance the cooling system?


This engine has the "power cooling" valve which is operated by the throttle position linkage. It seems to affect the cooling system. I am not certain precisely what action takes place in this valve. I would appreciate an explanation.

Thanks,

--Jim Hebert

[SEAHORSE]

Your throttle lever is connected to a rotary valve that has 3 fittings on it; pressure water in, a line from the thermostats, and a line to expell water into the exhaust housing.

At idle and below about 1800 rpm, the valve directs "cool" pressurized water to the rubber thermostat diaphragms on each cylinderhead. The pressure against the diaphragms push thermostats against a rubber seat blocking any water flow out the head unless it is warm enough to open the thermostats.

As the throttle is opened, the valve starts shutting off the pressurized water to the thermostat diaphragms, and allows the draining of the water behind the diaphragms. That then allows the thermostats to come off their seats and water flow out the cylinderheads, cooling the motor down as the power increases. Normally the motor then cools to about 25-40 degrees hotter than the incoming water when the boat is on plane.

The thermostat "nose" has small grooves in it to allow air to bleed off and fill the engine block completely to also help cool the voltage rectifier/regulator. If the motor develops an "air pocket" in the top of the block, the regulator can overheat.

In '93, the whole block design and cooling system was changed, as well as the pistons and porting.

[jimh]

Thanks for the explanation. I will append it to my maintenance manual so it will help me understand that portion of the cooling system.

[ChampioNman]

Yep what Seahorse said you have an open deck design, 93 and up went to a closed deck design. And eliminated the the power boost valve.

[JoePA]

Not to highjack a post but which block or setup is better? I'm running the same style engine and just curious? Isn't the closed block style that need the 2 size larger jets in the #2 carb?

Joe

[ChampioNman]

I like them both, the closed deck in my opinion is a better design and that's is the one that needs then bigger jet.

[SEAHORSE]

Hey CM, just to stick a knife in your back and twist it a bit, don't you remember the bulletin about richening up the #5 and #6 jets in the '92 and earlier big block V-6's to avoid detonation if overpropped? For the redesigned '93 closed deck block, #5 and #6 had slightly lower compression to avoid detonation because of exhaust tuning.

#2 cylinder would have problems sometimes because it is the vacuum source to pull the oil residue from the bottom bearing, thru the check valve, and up to the upper bearing, then into the #2 intake manifold. Any leakage from the bottom crank seal would allow water and exhaust up thru the bearings and lean out and/or damaage #2 piston big time!

[jimh]

Please clarify what the "deck" is, and what is the difference between open and closed decks.

[ChampioNman]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SEAHORSE &raquo;</TD></TR><TR><TD CLASS="quote">Hey CM, just to stick a knife in your back and twist it a bit, don't you remember the bulletin about richening up the #5 and #6 jets in the '92 and earlier big block V-6's to avoid detonation if overpropped? For the redesigned '93 closed deck block, #5 and #6 had slightly lower compression to avoid detonation because of exhaust tuning.

#2 cylinder would have problems sometimes because it is the vacuum source to pull the oil residue from the bottom bearing, thru the check valve, and up to the upper bearing, then into the #2 intake manifold. Any leakage from the bottom crank seal would allow water and exhaust up thru the bearings and lean out and/or damaage #2 piston big time!</TD></TR></TABLE>

Yeah I do but on the old OD it was less prevelant than the CD's.

But nothing replaces good motor maintenance, and people don't want to take down time for following the maintenance procedures.

You can pull the knife out a little and just twist it to the left I think you may have missed my left kidney .

[ChampioNman]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jimh &raquo;</TD></TR><TR><TD CLASS="quote">Please clarify what the "deck" is, and what is the difference between open and closed decks.</TD></TR></TABLE>

Jim, if you pull your heads you will see open water journals in your piston side of the block and you can kind of imagine the H20 flow around the jugs. On a closed deck the H20 journals are closed but have drilled out H20 passages. There are other internal changes to the block but that is the basics.