Can a fried impeller cause this??

Last week I went down an extremely shallow channel that I had to idle through. The bottom of the channel was muddy and I eventually turned around and went back. By the time I idled back the motor was obviously hot from going too slow for too long. I felt the tracking fins and prop scrape a few things but they both looked fine when I got it back on the trailer. All week long I was a little concerned that I possibly fried the impeller with all of the mud/sand that it pulled through.

Well this morning I dropped it in the water and got about 500' from the dock (doing about 30 mph) and the temperature shot all the way up. At that point I could see a little smoke coming from the engine so I stopped and headed back for the dock (At that point I knew I'd be replacing the impeller). I didn't want to go too slow thinking that a little water would get through and cool it off, but as soon as I gave it a little gas it would bog down so I had to idle back.

My question is does the motor have a sensor preventing it from working too hard once the temp gets too hot?

Thanks in advance.

Sounds like a fried impellar or a clogged raw water intake.

It's a clogged trans cooler, mine has done it a couple times too. Super easy fix pull the wall out of the V-drive compartment on the drivers side of the engine. On that side of the motor towards the front you will see a black tube you can either just pull the water intake line off the front of it or remove the trans lines and both sides of the water intake hose and pull it all the way out. With as much stuff as it sounds like you've got in there I'd pull it out all the way. it has a screen on both ends out it pull what you can out of the front and flush it real well both ways with a hose to get the rest. If you only made it 500' from dock your impeller is probably fine. The bogging down is a limp mode in the ECU that will keep it from running over about 1200 rpms if the temp is over 180. Good luck

I would at least check the impeller. It can not hurt anything!

Your boat has a "limp" mode to protect from overheat. Mercruiser also has a water flow/pressure sensor if the impeller goes out you get a double beep every 30 seconds.

I did the exact same thing, but my 2004 Mobius LSV has a strainer(clear plastic container, like a jar, with a strainer inside) on the water intake. The engine had sucked in sand and mud that completely filled the water strainer. Had to remove the strainer and completely wash out all the sand and mud. You may have the same situation on your boat.

Thanks for the info. And Pete, that does sound like an easy fix. Is the trans cooler the first screen in the whole cooling system? I was wondering why it wouldn't clog up anywhere else.

Nice pic by the way....my wife wants a damn hammock on the boat now..!

I pulled out the trans cooler and sure enough, it was clogged up with crap. I had to take the whole thing out of the boat to really clean it. I hope that worked....Thanks again Pete.

....and once again, working on the motor is the only time I wish I had bought a D-drive.

Eric,
Yup that's the first screen, mine has clogged twice now. The first time it ended my day, the second time it took me about 5 minutes to fix, didn't even pull out of the water to do it. A water strainer in the intake line before the trans cooler will prevent that, I still haven't gotten around to putting one on there though.

If you have a fake a lake for the boat or a flush system on it you can check the impeller without pulling it apart. Once you've got water on it run the boat up to temp and put your hand on the impeller housing. If it's cool you're good to go, if not go ahead and replace it.

The ladies always love the hammock. I found that thing Wal Mart for about $20 right before I left on a boat camping trip. It gets a TON of use, and a lot of second looks!

I used to have to clean that tranny cooler all the time. Instead of pulling it off you can take off the hose at the other end and run garden hose water through it backwards. However, usually just cleaning out the weeds from the "in" side does the trick. IMO

I'll probably just pull the hose off the other end of the trans cooler and spray it out next time. Taking the whole thing off sucked, but probably had never been done before so it needed it.

(Message edited by cinder1995 on May 29, 2007)

Well let me throw a different point of view at you from the performance world..

Your pickup's can pick up all sorts of debris. There are some kinda thorny plants in fresh water that will actually destroy a water impeller in no time flat. It's recomended in I/O boats that you change the impeller every season. I'm not sure if it's the same in inboards, but honestly I can't see it being much different.

We all love our boats regardless of their different breeds. The motor in our boats is arguably the most expensive thing in the boat!!

So to go along with my "fuel seperator" advice, plumb one of these bad boys up in your water system, and your problems will be solved.

They catch any large debris that can ruin an impeller, etc.. Plus you can just look down in them and visually make sure that your motor is getting water!

http://www.rexmar.com/page173.html


http://www.stainlessmarine.com/strainer4.html


They seem kind pricey, but both I put up are top of the line, add a nice appearance, and give you peace of mind on your motor. Cheap insurance if you ask me.

RD