in-line 6 overheating problem

[moneyhole]

Hey folks...I just got a 1977 V-20 cuddy with the Merc in-line 6 that was installed in 2008. It came with the engine that was pulled out as well - both are the 4.1 250 6 cyl. She has almost 3 hours on it and I went to perform all of my routine tests before I take the maiden voyage. Charge the batteries, plug in, and decided I better "yard check" it first. I put the water muffs on and turned on the water after I closed the two ports -one on heat exchanger and the other one on manifold. Boat fired right up but the temp guage started to rise after about 5 mins or so -160 then 200 then 220 - I shut her down. I saw one very small drip of antifreeze on a hose coming from the coolant fill. After it cooled down I opened the ports and nothing drained out. Do I start checking the stern drive water pump or the engine's water pump? Never owned a inboard with the heat exchanger set up before. Help would be great

[brisboats]

Bypass the hose coming to the circulating pump and you can determine which is the culprit. Either circulating pump on the motor or the waterpump. I hate muffs and would probably dunk her anyway with a temp laser aimed at the sending unit. Amazing how many boats un cool in the water as opposed to out. When you pull the hose to bypass if it is dry inside you aren't getting water up from the lower.

Brian

[spareparts]

Fisrt of all, I haven't seen many inline 6 motors with closed cooling, post up a pic of hte set up if you have it. If it hasn't been done within a year, go ahead and replace the raw water impeller in the lower unit. If the blades are broken off the pump, make sure you find them all. i wouldn't mess with teh ciruclation pump or the closed cooling till you know for sure you have good water flow to it. Odds are, its the raw water pump

[moneyhole]

Thanks for replying to my post so quickly. It has not been run but 3 hrs since 2008 - after the gentleman changed out the engine, prior to me buying it. I will click a picture of the 3" heat exchanger and coolant system tomorrow and see if I can learn how to post pics on this site. Like I said, with 60 psi on the muffs and opening the manifold and h. exchanger port and no water coming out at all, I suspected the stern raw water pump. Who is the best place to deal with on Mercruiser parts? I'm in Va - near Richmond. Thanks

[Destroyer]

Originally Posted by moneyhole

I will click a picture of the 3" heat exchanger and coolant system tomorrow and see if I can learn how to post pics on this site.

Open an account (free) on photobucket (www.photobucket.com). Upload your pictures to your account. Click on the pic(s) you want to show here. In the bottom left corner of the pic you'll see a box with various tag lines in it. Select the tag line that starts and ends with img. Copy that entire tag line and post it in your post here. (So it will look something like [img mypicture img] make sure you have the brackets [] before and after the img tag. That's all there is to it. Looking forward to seeing your boat.

[moneyhole]

I posted some pics of my boat-only had 1 of the motor. How expensive is it to have the lower unit water pump replaced if that is my problem? I have the in-line 6 with the heat exchanger and I'm not sure of which outdrive I have as it was painted over-completely with black paint. I had the muffs on -fired the boat and after 5 mins she climbed to 160, 180 200 then I shut it down @220 degrees or so. I let it cool off and placed a tub of water covering the intake lower unit holes and it bubbled some but temp still climbed. I didn't let it get anywhere near as hot and called it a day. I really want to fix her- it's been re-wired bow to stern, engine swapped in 'o8 with a known good running engine, but I did go thru the parts today and realized they used the old engine t'stat. That was cheesy. After it cooled down, I opened the drain ports & it had no water what so ever in the heat exchanger & I'm sure the manifold as well. What are ya'lls thoughts? Greatly appreicate them.