Mercruiser 4.3 Overheating

[adamk523]

I have a 1996 Larson 280 with twin Mercs. One of them started overheating this weekend. When I brought the throttle down, The temperature dropped. The temp readings went from 100- 250 on and off. When I finally got back to the dock, I turned the key off, but the engine kept sputtering and did not shut off immediately. I recently changed the water pumps in the out drives, so I doubt that is causing the overheating problem. Not sure if the sputtering could be related?

 

[Haut Medoc]

Re: Mercruiser 4.3 Overheating

What kind of mercs? Are they fwc or raw water cooled? Did you have any over-heating problems prior to this episode?...J

 

[adamk523]

Re: Mercruiser 4.3 Overheating

Never overheated before. They are raw water cooled. I did not see any seaweed on the intake. When I was running, the temp was good for about 30 minutes. Then it started creeping up to 250 and the alarm went off. I lowered the throttle, and the temp dropped to 125. It then went up to 175 (normal operating temp). I was running at about 3800 rpm. Other engine was fine. When I pulled into the dock, and shut the engine, it did not shut off all of the way. I turned the key and the engine ran normal then shut off completely when I turned the key again. Might be the timing?

 

[Haut Medoc]

Re: Mercruiser 4.3 Overheating

You still haven't said specifically what engine you have. What is the rated horsepower? When was the last time you had the risers off to look for corrosion inside? If you live in Brick that means salt water. If you have a trailer, put it on the muffs, remove the water hose that goes from the transom to the water pump and check for water flow. You could do this in the water except you probably don't want salt water in your bilge, that's your call. If the flow looks steady, then I would say that you have a restiction in your manifolds/risers. Check for blockage at the water dumps on the risers. This is where I would start. Hope this helps.....J....P.S. I used to live in T.R.....

 

[Haut Medoc]

Re: Mercruiser 4.3 Overheating

4.3 Duh!!!

 

[adamk523]

Re: Mercruiser 4.3 Overheating

Mainfolds and Risers were done last year. The engines are merc 4.3 LXi . I think they are 260 HP<br />Could it just be a thermostat?

 

[Haut Medoc]

Re: Mercruiser 4.3 Overheating

I doubt it, but....They are easy enough to change...It couldn't hurt....Did you check water flow? Also the risers (though new) can still get restricted from crud that comes from a nine year old salt water block. Check your inlet flow, change the t-stat and see what happens....J

 

[adamk523]

Re: Mercruiser 4.3 Overheating

Wasn't the thermostat. The dealer checked it out and said that the hose inside the outdrive was sucking air. They are replacing the hose. Since they had to take the bell housing off, I decided to have them change the bellows and shift cable. $$$$$$$$$$$$$$ Repair

 

[Haut Medoc]

Re: Mercruiser 4.3 Overheating

You didn't check the water flow, didya? You would have seen lots of bubbles and a weak flow. Live & learn, right? Wise decision about the bellows & shift cable. I'm curious; how many hours did they charge for labor,"since they were all ready in there?" Catch a fluke for me!....J

 

[ROBBIE LEE]

Re: Mercruiser 4.3 Overheating

hI GUYS I HAVE A PROBLEM WITH MY 2004 MERC BRAVO 3 WATER PSI IS LOW ON TICK OVER 1.0 PSI I HAVE NOTICED THE INTAKE PIPE TO MY RAW WATER PUMP IS FULL OF BUBBLES OR AIR WHAT CAN IT BE CHEERS

 

[Don S]

Re: Mercruiser 4.3 Overheating

Start a new thread ROBBIE LEE. don't just find an old 2005 post and tack onto it. Your question will be lost forever very quickly as people answer the original question and never see yours.
Please turn off the cap lock. Makes it very hard for people to read.