Overheating? Mercruiser

[DayCruiser]

Hello again,<br /><br />3.0 Merc cruiser i/o Alpha 1989 motor, 4 cylinder<br /><br />Ok Carb rebuilt and short in emergency cut off switch fixed and new starter solenoid. Runs like a scalded dawg..but and there is always a but in the Days of the Cruiser lol Running in a long no wake zone motor creeps up to 172 degrees before end of zone and then speedily goes back down when speed was increased. I don't know if this makes a difference but the trim was not down completely and a load of 4 people. Generally goes to 140 under bridges and WOTs out at 135 deg.<br />Question that I searched and couldn't find a consensus--what is the normal operating temp and what is the temp damage occurs?<br />Is this something to keep watch on until winter repair(and no long idleing) Or is it something that needs immediate attention.<br />From reading it is symptoms of a weak water pump and or impeller.<br />Thanks in advance!

 

[crazy charlie]

Re: Overheating? Mercruiser

Sounds like a rwc motor.You are running warm on idle .If you are in salt, have a problem with crystalization just shy of 190..The salt crystals can block things up and lead to problems.Many fwc motors run at 160 -190 range.You may want to start with something simple like changing out the tstat and taking a good look at the housing for rust inside.Pull the top hoses fromm the tstat housing and remove and clean the ball spring rod set up if you have one.Charlie

 

[tommays]

Re: Overheating? Mercruiser

Sounds like a weak water pump not enough flow at low speeds<br /><br />If you were cloged you would tend to get hot at high speeds when the motor is working much harder<br /><br />The t-stat is a 140 and i run about 150 most times and drop to about 135 at low speeds<br /><br /><br />tommays

 

[thunderroad]

Re: Overheating? Mercruiser

don't anyone take this wrong because I'm strictly being curious. What is the specific danger you face if you run a marine engine at 180-190? They seem to be pretty much brothers with automotive engines which can handle those temps easily. Is the raw water cooling system an inefficient design? Maybe it doesn't keep the temperature even throughout the engine. Like I say...I'm just curious enough to ask a stupid question.

 

[crazy charlie]

Re: Overheating? Mercruiser

Originally posted by crazy charlie:<br /> Sounds like a rwc motor.You are running warm on idle .If you are in salt, have a problem with crystalization just shy of 190..The salt crystals can block things up and lead to problems.Many fwc motors run at 160 -190 range.

By the way...its not a stupid question

 

[tommays]

Re: Overheating? Mercruiser

It will start to "cook" out the minerals in some fresh water and salt in saltwater <br /><br />Over time they will build up in the motor and cause problems<br /><br />Look at all the problems a car motor has running nice clean straight tap water after a year or so <br /><br /><br />tommays

 

[DayCruiser]

Re: Overheating? Mercruiser

Thanks for the info! Ya its fresh water/external.<br />I am just going to stay away from the Marina long no wake zone and keep the temps closer to 140. Hopefully it will last until winter repairs.

 

[tommays]

Re: Overheating? Mercruiser

i would not put it OFF its giveing you a really nice early warning <br /><br />If you let it go and shread some pump vanes you will find your self in a spot at the worse possable time LIKE A BIG THUNDER STORM or just do some really bad and needless overheat dammage<br /><br />tommays

 

[crazy charlie]

Re: Overheating? Mercruiser

If you are not planning on attempting to troubleshoot it this usage season...Then...When you are in the middle of a long no wake zone,put er in neutral and bring the rpms up for 20 seconds or more .The temp will usually decline rapidly and then you should be good for the rest of the zone.Charlie...been there-done that

 

[DayCruiser]

Re: Overheating? Mercruiser

Thanks for the advice, tommays and crazy charlie. We will see how it goes this weekend. I need to at least have some more fun before back to shop lol

 

[CaptRon66]

Re: Overheating? Mercruiser

If you have access to see the coupler and driveshaftyou can sometimes see a difference in rpm between the 2. This happened with me a ways back. I tied my boat tight to the dock and put it in gear at idle. Slipped like crazy and made noise.

 

[DayCruiser]

Re: Overheating? Mercruiser

Well tommays pushed me over the edge lol I will use it this weekend and get it out Monday for repairs...better safe than sorry. Have it back in by next weekend

 

[DayCruiser]

Re: Overheating? Mercruiser

Update:<br />Went to replace thermostat--there was not one. No wonder boat never reached 143 degrees at WOT. Replace and now does.<br />Checked impeller. Impeller was bent out of shape all over with cracks and a couple of chunks missing. No wonder boat was reaching 170+ in the no wake zones.<br />I haven't took a long trip yet but this better be the fixer for the rest of the summer lol<br />Thanks for all the help!

 

[akaSharkey]

Re: Overheating? Mercruiser

Bet your glad you listened to tommays. That preventive maintence is cheap comaped to a rebuild. From what I hear the Mercury impellers are good for about three years

 

[DayCruiser]

Re: Overheating? Mercruiser

Originally posted by akaSharkey:<br /> Bet your glad you listened to tommays. That preventive maintence is cheap comaped to a rebuild. From what I hear the Mercury impellers are good for about three years

Ya tommays you da man! special thanks!<br />This is true about putting out the little fires before they become big ones lol I am learning that fast in life. We are also keeping a log of the repairs and maintenance so we will know appx when the next maintenance is due