Mercruiser 454 overheat problems

[billeehines]

I have a 1984 Sea Ray Amberjack with a 454<br />big block. It has a trans connected to a bravo<br />outdrive. I think the engine is original (660 hrs)<br />and outdrive replaced in early 1990's.<br />I purchased boat from a broker in July 2003.<br />Everything worked great upto pullout in end<br />of October. In spring engine started and ran<br />great. On second run in my yard, engine ran<br />to hot after 5 minutes of running. I turned off<br />and replaced thermostat. Restarted and<br />everything was running normal. Dropped boat<br />in water a few days later and went fishing.<br />I noticed heat gauge went up to 3/4 but not<br />to hot. Anchored up, fished about a half hour.<br />Boat would not start, turned over very slowly.<br />Bought new starter, boat started and went<br />fishing a few days later. Same thing happened, only this time boat would not<br />turnover. Pulled plugs, water in all cylinders.<br />Towed back to dock, mechanic came and<br />serviced engine, changed manifolds and<br />risers and now boat is running. I ran for<br />about 1/2 hour and heat gauge showed<br />normal BUT I checked manifolds and found<br />HOT (not burning) but possibly 160 or 170<br />degrees. I have a thru haul fitting on the<br />starboard side (1 1/2") hose feeding the<br />starboard side. That manifold was about<br />110 degrees with the riser about 160 or 170<br />degrees. The port side manifold was 160/170<br />degrees and the riser was 110 degrees.<br />I put on a new engine water pump, but still<br />have the same problem. I'm afraid to make<br />a long run fishing trip because the temperature in the manifolds may rise and<br />burn them up again. Any suggestions?<br />BILL

 

[billeehines]

Re: Mercruiser 454 overheat problems

After receiving no help from anyone AND <br />MY MECHANIC saying I have no idea, I decided to solve the problem myself.<br />First I removed all the hoses and coolers (2),<br />replaced the impeller (although it was good)<br />replaced the hoses and coolers and thermostat (t-stat was new in April 04).<br />Started boat and STILL HAD THE PROBLEM.<br />I noticed the manifold hoses on the starboard<br />side were connected opposite those of the port side. The port side ran HOT, so I switched those hoses to match the starboard<br />side hoses. THAT WAS THE PROBLEM!!!!<br />The manifolds (BOTH) run very cool.<br /> The former owner had switched them probably when changing the thermostat.<br />These connections are about 3 inches apart<br />and could easily be switched. On short runs they would NOT GET HOT ENOUGH<br />TO BURN UP . BUT, on my first long run they did burn up and that mistake cost me about $2000.00. When purchasing a used boat, don't assume ANYTHING is correct <br />CHECK IT OUT IF POSSIBLE. Many boaters<br />do their own repairs and this can happen.<br />BILL