Need Help Overheating and other problem

[sluketic]

I put my girlfriends parents boat in the water over the weekend. It is a 1989 19ft Maxium with a 1989 4.3 V6 mercruiser Alpha 1 outdrive. I noticed the temp gauge rise very fast to about 170 and stayed there when cruising about 30mph, when I slowed to about 6 mph it went to about 220+, and back to 170 180 when cruising. Also when docked I raised the outdrive with the trailer button all the way up and heard water leaking into bilge area, lowered back down and it stoped. Please let me know if you have any info that could help me fix the problem.

Thanks, Scott

 

[thrasher]

Re: Need Help Overheating and other problem

I suspect the impellor in the outdrive is not working correctly (probably worn out), this will prevent water being pumped up to the engine when idling, causing high temperatures, as you sopeed up the engine the pump will work a bit better and bring the temperature down. Plan on changing the impellor (its easy to do and not very expensive).
I suspect that the prop shaft has a split in it, when you raise the outdrive it will stretch the bellow causing the split to open and allow water into the bilge area, as you lover the drive, it will compress the bellow and reduce the size of the split, slowing down the flow of water into the bilge.
I think you need to plan on removing the outdrive (about half a dozen bolts), check the bellows and the universal joints on the drive shaft, and whilst the outdrive is off replace the impellor.

Gary

 

[sluketic]

Re: Need Help Overheating and other problem

Thank you Gary for the info! Not sure how to make the repairs, is there a manual online that I can use for this engine and outdrive? Or what manual should I purchase? Looked around and there are a couple different publishers out there witch one is best?

Scott

 

[thrasher]

Re: Need Help Overheating and other problem

I am not sure if you can get the outdrive service manual online (probably can as it's getting quite old) hopefully someone can give a link to the manual.
I purchased a SELOC manual and it was a complete waste of money (others will disagree). I would strongly recomend you purchase the mercruiser manual, I now have one for my engine and another for the outdrive and there is nothing I cannot find in them, well worth the expense.

Gary

 

[95yj]

Re: Need Help Overheating and other problem

Here's a place to start for the manual: http://www.boatfix.com/merc/Servmanl/14/14b3.pdf

You might need to browse around to find your specific manuals needed.

 

[Don S]

Re: Need Help Overheating and other problem

Wrong manual there 95yj, that is for an Alpha I Gen II drive, 91 and newer ............... big difference.

Here is the one for the older Alpha I drives
http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

To use the manual, click on the link, scroll down to the manual outline and click on the LETTER to the section you want to view.

 

[95yj]

Re: Need Help Overheating and other problem

Thanks Don for pointing to the correct manual. I just gave the link for him to start looking for his manual as I'm too lazy to do the search myself. Hence my statements in the original post.

 

[MFE]

Re: Need Help Overheating and other problem

Hey guys, looks like a lifesaver of a forum here so thanks to those who own, maintain, and contribute.

I have a related problem on an early 70's Grew 194 with a Mercruiser 165/chevy straight 6...sounding a lot like the water pump impeller, as it started running warmer this season, will cruise all day at 3000 RPM at about 165-170, but as soon as it's backed down for idle or docking it goes over 180, I've seen as high as maybe 200-210 briefly prior to shutdown. Aside from this the boat is running like a champ.

I have seen some repair manuals online, and if I were anywhere near my own tools or my own place, I might tackle it, but as it is I'm far away from my tools and a little out of my comfort zone. So a marina will probably do the work, but it's taking time to get scheduled.

So...the bottom line question is this: how hot is too hot? Do I need to dock this thing or can I keep running it until the service is scheduled if I keep an eye on the temps?

 

[95yj]

Re: Need Help Overheating and other problem

On a closed cooling system motor, (has a heat exchanger that acts like a radiator), you can run around 180 with no issues. Most raw water cooled boats, (sea/lake water gets pumped through the entire engine to cool it), have a 140 or 160 degree thermostat. The reason for running cooler is since outside water is just pumped through the motor, the motor can develop "hot spots". If the engine is run with a hotter thermostat, or is slowly overheating for that matter, these hot spots will be that much hotter.

Another issue is that the impeller that is failing can be brittle and just decide to break up. At that point, it clogs everything up and needs to be cleaned out, but more importantly, you instantly have no cooling. Now you have to shut off the boat and get towed in or you risk a $5000 repower because you didn't do a couple hundred dollars worth of maintenance.