Peculiear overheating issue

MAJOR SETBACK!!!

Turns out the hose from the outdrive to the transom was cracked/leaking at BOTH ends. Just old I guess, but the horizontal gimbal pins were driven in so tight they won't come loose. I have the 'tool' to remove them but the splines on the inside have been rounded and a new tool just slips in the socket (both sides) - Can't change the hose without removing the gimbals. Anybody got any bright ideas how get around this problem?
 
Update:

FINALLY!!! Got the gimbal pins out - ended up drilling them out - what a production. Sure enough Locktite in excess - no way were they coming out without drilling. Reassembling everything tomorrow - new transom bell housing kit, bellows, hose, straps, etc., then remounting the out drive.

The threads in the gimbal ring were completely covered in Locktite - totally overdone by the last one to do the boot replacements. Those pins were NOT coming out by any conventional means. I was there during the entire removal process. A retired machinist friend with all the right equipment and machinery got them out without disturbing the original threads - facinating to watch, but done exactly right. With all the rubber parts being replaced it should be good for another 10 years and next time they need replacement the gimbal pins will come out without a problem. One drop of Locktite is all that is required to hold them in place, not a gallon as was apparently used.
 
njmello said:
Update:

FINALLY!!! Got the gimbal pins out - ended up drilling them out - what a production. Sure enough Locktite in excess - no way were they coming out without drilling. Reassembling everything tomorrow - new transom bell housing kit, bellows, hose, straps, etc., then remounting the out drive.

The threads in the gimbal ring were completely covered in Locktite - totally overdone by the last one to do the boot replacements. Those pins were NOT coming out by any conventional means. I was there during the entire removal process. A retired machinist friend with all the right equipment and machinery got them out without disturbing the original threads - facinating to watch, but done exactly right. With all the rubber parts being replaced it should be good for another 10 years and next time they need replacement the gimbal pins will come out without a problem. One drop of Locktite is all that is required to hold them in place, not a gallon as was apparently used.
Click to expand...


sounds good....keep us posted and let us know how you do in the upcoming tournament...

cliff
 
Cancelled the tournament plans - after replacing and reassembling everything the problem still exists only now it doesn't remain normal until upping the revs. Engine warms up, slight 'bump' in gauge when the t-stat opens and even at idle climbs right into the red, non-stop. Visual check shows there are no water leaks anywhere and there is water coming out the exhaust. I did change the automotive water pump to marine .

Getting a lazer temp gun today - start pulling hoses - compression check is next, then the logs if that checks out.
 
Last edited:
if you have not done so already you may want to pull the exhaust manifolds and risers to see if one of the exhaust flaps has broken loose and is blocking some of the water from flowing through the exhaust....

cliff
 
Got an IR temp guage today. First I'll check the incoming raw water line from the transom to make sure there is sufficient flow there.

I'll pull the plugs and give them a visual when I check the compression - probably need new plugs anyway. Removing the exhaust manifolds comes after the compression check. I usually take them off, give them a caustic soda bath and new gaskets every 3 years of so. Only been two years since last 're-do' - could be a problem, though. It's just odd that the temp no longer holds normal at idle anymore.

I plan on disconnecting the raw water 'in' line at the power steering cooler to check the inflow. Running the engine a few minutes should show if thereis a restriction . If it checks out, I'll disconnect after the cooler and make sure the flow is the same; I've already checked all the hoses to the manifolds - they are unrestricted.
 
Problem solved!

I actually found the culprit today. After changing every moving part in the cooling system and every picyune problem area in the process - the overheating problem changed from normal at idle and overheat at higher RPM to directly to overheat from start up.

CLUE: Something 'moved' in the cooling system to block the open flow of water. The ONLY item never checked was the thermostat BLOCK (the part the t-stat sits in) that all the exhaust cooling lines attach to.

After thinking about the 'problem' - today I disconnected the raw water hose at the power steering cooling, started the engine (cold), and water pumping out immediately; revved the engine water volume increased. OK - Good water supply coming from the outdrive. Reattached the hose and disconnected it at the circulating pump - restart, good water supply, more water at higher RPM. Reattached the raw water hose and loosened one hose to each exhaust manifold - restart the engine - just a dribble getting to the manifolds. AHA!! Removed t-stat - tied everything back up, restart, still just a dribble at the manifold. Disconnected all the hoses from the t-stat block - removed it and sure enough - the passage between the raw water in and the circulating pump was encrusted with rust, so was the 'bypass', but not as bad. Apparently the engine got just enough water through the bypass to maintain normal temperature at idle, but flow was constricted at higher RPM. Some chunk of rust scale must have been dislodged during the repairs that ended up choking the only remaining opening in the flow line.

So I prepared a caustic soda bath, hooked up the block to the battery charger and let it 'cook' all day. Eight hours later the t-stat block was as clean and smooth as a baby's bottom, inside and out and about a quarter of a pound of iron filings in the bottom of the bucket.

Touched it up a bit with a wire wheel, some new high temp paint and will reinstall it tomorrow. I am confident the problem has been solved.
 
Last edited:
NJ
Glad you found your problem!
Hate to say I told you so, but...go back and read post #19 from May 26.
 
Still overheating!!! Heart to heart with the Merc Tech today - he drags out the manuals. Mercruiser 260 requires minimum 4 gals a minute at 1000 RPM for cooling. Disconnect the raw water hose at the T-stat block - start the engine - only get 1/2 gallon.

OK - Tech dragged out the manual. My engine requires 4 gals a minute minimum at 1,000 RPM. I pulled the raw hose at the t-stat block - ran the engine 15 secs - only got about 1/2 gallon.

Reconnected the hose to the t-stat block - disconnected the raw water at the power steering cooler (in side) - same 1/2 gallon.

Auto store in the morning to get a couple of feet 5/8" hose. I can disconnect the raw water hose at the outdrive and see if the impeller is pushing 4 gals a minute BEFORE it gets to the transom. If the impeller is pushing to spec the 'constriction' is in either the hard pipe going through the transom or the hose from the transom to the PS cooler. If the impeller is NOT pushing spec, I don't have to take apart the gimbal housing, but the outdrive will have to come apart to see where the problem is.
 
I directed my father to this thread to see if he remembered the problem he had way back when. He did. Here's what he had to say...

The problem was located in the thermostat housing. One of the walls had rotted through disrupting the flow through the normal route. The hot water was not being discharged but was being mixed with the incoming cooling water. Easy fix. simply change the housing.
 
I checked the housing, and it did clean up rather well with the homemade caustic soda - electrolosis bath. The engine simply isn't getting enough water volume to the T-stat block. It's either a restriction in the outdrive or between the outdrive and the inside raw water hose. I'll know which it is tomorrow and begin the appropriate repair.
 
no mention of replacing the water pump base, or inspecting the copper tube for holes, or inspecting the water pocket cover for leakage.
 
You must log in or register to reply here.

Forum statistics

Threads
113,183
Messages
1,428,099
Members
61,091
Latest member
dionb
Back
Top