470 Mercruiser overheats

Having problems with this 470 Merc. Originally had simple overheating due to a leaking heat exchanger. Replaced with upgrade 4" unit along with impeller and T-stat. Ran at 180 degrees for several minutes on the lake then began overheating, finally turning to steam by the time it reached the dock. We have already blown HP air thru the water passages from the outdrive water tube to the hose coming off the regulator. Currently replacing the upper portion of the water pocket cover assy but quickly running out of ideas. Wondering if perhaps there is something common to explain this problem?<br /><br />Talk about a head full of steam!

Re: 470 Mercruiser overheats

Head gasket. Had the same problem on my 470 about 20 yrs ago. Don't turn the engine over while you have that 460 Lincoln head off. If I remember right, the cylinders are held in by the head, and you can break the seal at the lower end. I used Copper Coat gasket sealer on down side of the head gasket, if memory serves me correct. A manual would be a "must" for this job.<br /><br />She sure gets hot, doesn't she? Pretty quick, too! Mine melted the overflow jug.<br /><br />Good luck.

Re: 470 Mercruiser overheats

Hey Grant, Had a simaler problen with my 470, It turnd out to be the (exused elbow) was so clogged up with rust that the water could not flow out of the system! If water can not flow out freely, It can't enter.<br /><br /> Hope this helps you, (Skelly

Re: 470 Mercruiser overheats

Been thinkin' some more. If it's not really heating up and blowing steam into the coolant reservoir with a vengance, it may not be the head gasket.<br /><br />If I remember right, it is possible to install those heat exchangers backwards, end-for-end. If you do, the water fittings end up reversed. Then coolant and cooling water will run thru the wrong sections of the exchanger, resulting in significantly reduced cooling. Check that out before you start tearing things apart.<br /><br />Hope your luck is better than mine!

Re: 470 Mercruiser overheats

Hey Grant! sorry I meant (exhaust elbow)<br />Its only 4 bolts & a Clamp.- check it.there should be more than just mist comming out exhaust.I went through the the hole works just as you are doing . heat exchangers are not cheep!<br /><br /><br /> Hope this helps you. <br /> <br /> Skelly<br /><br />

Re: 470 Mercruiser overheats

Hello Grant!<br /> Just wondering if you got your 470 fixed yet, If yes . What was the Problem? <br /><br /><br /> Thanx, Skelly

Re: 470 Mercruiser overheats

Skelly,<br />Still working on the motor. Decided to remove the head and replace the gasket. Had a long wait at the machind shop getting the head tanked and magnafluxed. Then had to wait for the gaskets to come in ( ever since the WTC disaster we've pretty much had our shipping time double ). Hopefully I'll have a fresh reply for you by midweek. I'll be sure to let you know!<br /><br />God Bless The USA.<br /><br /> Grant

Re: 470 Mercruiser overheats

Grant, after you get the head back on (I hope you read the manual, as I remember, it was pretty specific with regard to sealers, etc.), make sure the exhaust manifold and riser are flowing water without restriction, as Skelly suggested. Also, check to be sure you installed that new heat exchanger the right way. It's important. I seem to remember an arrow on the side of it that points forward. The manual will help you with that, as well. Clean the head bolt and block threads really well, and use an accurate torque wrench. That's an aluminum block. Be careful not to disturb those cylinder inserts!<br /><br />Good luck!

Re: 470 Mercruiser overheats

SUCCESS!! <br /> Finally, after going through literally the entire cooling system we found the problem. Initially, the boat was overheating. Found that the heat exchanger was leaking the coolant out of the exhaust (prop). Replaced the heat echanger with a four inch unit that cools better than the three incher that came with the boat. Unit still overheating. Checked front water pump and found pieces of impeller around it. Tried again and still overheated. Replaced T-stat and tried. Removed head and inspected; still overheating. Replaced upper fitting on water tube; still overheating. Removed outdrive and blew high pressure air through the water tube....and something came out. Ran unit at the lake after this and had no problems whatsoever. Hate to have a motor do this to us for so long but at least we did manage to find and repair the problem.