Engine Alarm - Cooling Issue

jklein

Happy 4th Everyone.
Clearly based on this post it wasn't a "happy boating 4th" for me.
I have been chasing down an engine alarm for 2 weeks now.  I believe it to be a cooling issue...

I have a 2006 250EC with the Mag 350 Mercruiser.  About 2 weeks ago after boating over something floating a few inches below the surface (no wake speed) I started to hear an engine alarm at higher RPM's.  The horrible Faria gauges show that my temp is approaching 200 degrees when the alarm goes off.  Thinking this was clearly a cooling issue I had the mechanic come out.  He attached the computer and was perplexed.  He saw the alarms listed on the computer, but he said the numbers "were all good and in range?"  Hence he thought a bad sensor...

Replaced the sensor and assured me the boat was set for the 4th weekend.
Packed up the family including the 8 month baby girl and headed out.  Didn't make it 5 minutes on a plane without the alarm sounding and the gauge reading close to 220 degrees.  I idle sped back to the dock.

I am running the Bravo 3 - I had my cooling assay replaced 2 years ago...

Any feedback would be helpful.  Thanks in advance.

jklein

My rpm and speedo gauges jump everywhere. I contestantly have to flick the glass..

changing the the impellor is hard. So little room between the engine and transom wall. I changed the impellor 2 years ago. Is it common to go bad this fast?  Could it be anything else?  A thermostat maybe?  

raybo3

I would clean out the raw water heat exchanger. Very easy and quick to do. Take off both end caps and flush with water hose. Does not take much to cause temps to go high when on plane.

jklein

My fault - I have a raw water/salt water cooled boat. Am I mistaken that then I would not have a heat exchanger?

Dream_Inn

Nope, wouldn't have a heat exchanger.  Definitely could be an impeller.  If you have used it thru 2 summers, then it is time to change it out.

Stodge

Also check the thermostat.  Could be stuck or plugged up.  

rasbury

yep, 10-4 on that pump. I went through a heck of a time with mine....I had mine come apart and broke the belt even. I pulled the pump apart and it was broken but had all the parts so put it back together but sill was overheating. I ignored the grooving in the top and bottom of the housing as I just could not believe it would still not pump-but ran hot. I found a company that sells a wear plate top and bottom out of stainless and a shorter impeller to same from spending a 700 bucks on a whole new pump-kit is 100 bucks and seems to be working just fine....now I did manage to screw it up and had to replace it again- I was surprised how the new parts had scoured so when I had to take it apart again I did replace the wear plates just in case- it is a bugger to get that pump off! Seems to be fine now.....

jklein

Rasbury are you a 2006 250 EC also?  Any suggestions on how to reach the pump?  It is so cramped in their. The first time around I paid the mechanic and he charged a fortune for labor - yet when I saw the space he was working in I king of understood...

duane.mosley

i too have the 06 250ec, the pump wasn't that bad to replace. took me about 45 minutes to remove the belt, remove the entire housing/pulley and replace. i put a foam pad across the engine, put my knees on the transom, and laid over the engine. it took longer for my head to feel normal again then it did to change the pump assembly.

if your running fine at idle, and it only over heats when you try to get on plane, i would check your sea water strainer. i sucked up some mud in mine a month or so ago and it gave me a fit for about a week until i figured it out. i pulled the hoses off the power steering cooler, and all the fresh water hoses, heat exchanger, and flushed everything out. 

here is a link to the issue that i had. good luck
http://rinkerboats.vanillaforums.com/discussion/3708/over-heating-issues#latest

jklein

Duane - a very nieve question. I asked my certified mercuries mechanic after reading your original post (and pictures). He said my boat doesn't have a strainer???

Based on the picture I'm assuming it's an obvious part? Is my mechanic way off?  Do some versions of the mag 350 not come with one?

most importantly where would I find it?

LaRea

Some boats have dual water pickups (one through the outdrive, one from a thru-hull with a strainer).  Some have only the outdrive pickup.  

If you have one, there will be a thru-hull fitting with a shut-off valve near the keel in the back of the engine room.  The strainer would be an 8" diameter metal can with a glass top and two rubber 1-1/2" hoses attached to it.  It would be pretty easy to find, so I'm guessing your mechanic is right and you don't have one.

duane.mosley

here is a picture of the basket for my strainer. it is on the starboard side of the bilge. the metal basket in my original post goes in the brass pot. there is a lid with a glass center so that you can observe the flow through the stainer. if you have one, you can't miss it.

jklein

Thanks for the picture. Very helpful. Honestly I know that spot in my engine compartment and I do have a thru-hull valve but it clearly goes to my head. I just assume that's the water pick up for my toilet..?

following up with my mechanic he said, "only closed cooling engines have the second pickup?"  My boat is raw water/sea water cooled and I only have the out drive pick up.  

I will absolutely look again but I think in my engine compartment the only thru-hull opening I have is the one piped to the head.....

thsnks again 

raybo3

That is not a true statement. My boat is fresh water cooled and I only draw water from the outdrive. I do not have a strainer....

Handymans342

Maybe you should have both Ray? 

Handymans342

Good question for Al

raybo3

Why do I need both? I don't have an overheating problem.

Handymans342

So you have a raw water pump on the engine and a hose that runs right to the outdrive?

raybo3

Yes....

rasbury

I went through the same thing....I have a 1/2 closed loop system with a raw water pick up for the risers and heads- the raw water comes in through the thru hull and then the strainer and then into the raw water pump. From my previous posts, I have determined the strainer must be optional as some chimed in they had one, others did not. I then have water from the foot coming in as well so I have both, for a 1/2 closed loop system! Others only have foot pickup up for a normally cooled motor so go figure. Now, looking at the manual, there are like 3 different style risers which I have no understanding of and I'm sure that's where the answer would lay- probably depends on what style risers you have? 

raybo3

Al if Merc spec is for dual pick-up then why do I only have one from the outdrive? Its a 2002 342FV.

Dream_Inn

Ray, do you have horizon engines?  I've seen both setups on 342s (there are many of them in my marina).  Never thought about engine config.

Handymans342

Handymans342 said:

Maybe you should have both Ray? 

LaRea

I thought the dual pickup was for redundancy, not flow rate.  My Horizon 496's run great with the single pickup.  So if the Bravo III on its own can cool a 375-HP engine, that should be more than enough water for a 300-HP engine.  Right?

Black_Diamond

Raybo:  I have the 350MAG MPI. Only water pick up is thru the outdrives. 

Handymans342

So does the pickup thru the drive go to a strainer first? 

Black_Diamond

No strainer with the water inet from the drive. The holes in the foot keep out the big stuff.  Never had an issue except sucking up a plastic bag once. lol   

raybo3

I have the same set-up as BD. No strainers and water comes in from the outdrive. I do not have temp problems. Boat runs great..... I was just responding to Al's comment about the duel pick-up....

rasbury

on mine it does Handy- both the thru hull and the foot go into a Y into the strainer and then to the water pump. 2005, 350 MPI

Handymans342

Thats what mine has Ras. A Y mounted on the transom. 

LaRea

On the dual pickup, both intakes go to a y-pipe that feeds into a strainer.  On the single pickup, there's no strainer.