My first thread...merc overheating

[DockedPay]

New member but been reading for a while!..Problem..got a 1988 30' cruisers..twin 350 mercs, fresh water, raw water (lake water) cooled. New impeller, new 140 degree thermostat, oils clean and not milky. At idle port motor gets hot. Goes up to about 180 deg. If i give it throttle temp will go back down but climb again. If I put it in gear, temp really climbs and I shut it down as it nears 200 deg. so I don't damage motor. The mechanic who installed impeller was good enuf to come and make sure I had good water pressure from the drive (alpha 1) to the thermostat housing. Where do I go from here?? Guessing risers and manifolds but how do I flush them or check their not obstructed other than what I might see thats obvious?..Then where do I look from there?...Thanks for any help

 

[JCF350]

Re: My first thread...merc overheating

Get a infrared thermometer and check the manifold and riser temps. You'll find other uses for the tool, especially if you have a dog or varmint.

 

[Lakester]

Re: My first thread...merc overheating

Get a infrared thermometer and check the manifold and riser temps. You'll find other uses for the tool, especially if you have a dog or varmint.

hello,

jusr curious... how do u use the tool on varmits? i mean other than scan in dark? will it work on armadillos...???

regards
lakester

 

[PSS-Mag]

Re: My first thread...merc overheating

I use the laser on mine to mess with my dog or the kids F'in cats (AKA my unwanted varmints)....

But yea I seriously use it alot more than I ever thought I would for actually trouble shooting of all kinds of things. I've actually used it to find electrical shorts in the house. Even though the only sign was a sudden jump in electric bill. I was able to pin point an exact breaker that was getting much warmer than the others. So the $20 investment very well could have saved my house from burning.

 

[crouse77]

Re: My first thread...merc overheating

I had a similar problem on a 4 cylinder, so this might not work. Anyway, there is a hose from my thermostat housing into the manifold ( i only have one) I unhooked the hose from the thermostat housing an put a garden hose into it with a clamp on it. The water would barely run through the manifold. I ended up pulling it and soaking it in a big tub of muratic acid. That ate a bunch of the rust and crud up. I then power washed it out and it's all good now. I'm not mechanic so there are probably other things to look for, that's just what worked for me.

 

[JCF350]

Re: My first thread...merc overheating

hello,

jusr curious... how do u use the tool on varmits? i mean other than scan in dark? will it work on armadillos...???

regards
lakester

Varmints = cats

 

[DockedPay]

Re: My first thread...merc overheating

Thanks for the advise. I'm going to see if I can get my hands on one of those infared thermometers this week before I go taking anything apart. Any more suggestions are surely welcome!

 

[DockedPay]

Re: My first thread...merc overheating

OK...I used an infared thermometer and noticed the elbow above where the exhaust shudders are was running hotter than the opposite side. I took off the riser and flushed it out, and made sure the shudders were opening ok..put it back together and now both sides are running about the same temp...PROBLEM...ENGINE IS STILL OVERHEATING!..doing the same thing it. Now..at idle the temp slowly climbs..if I put it in gear, temp climbs alot quicker..In either case I shut her down around 190 degrees so I don't damage motor. NOTE: when at idle, and temp is high (up around 180 and climbing), if I give it throttle and bring the RPM's up, the temp will drop back to normal rather quickly. - But temp will just climb back up again. From this it seems to me that when I bring up the RPM, the motor is probably getting more needed water. So....what does this mean?..impeller?...note: the impeller was recently changed, and new thermostat (working properly)..I've also tried running it without thermostat - same problem...PLEASE HELP! I'm pulling my hair out. Also note: I have to pay to have boat hoisted out, so I'd like to be fairly sure the problem is at the outdrive end before doing that. Any guidance would be appreciated.

 

[airframer]

Re: My first thread...merc overheating

still sounds like your thermostat. sounds like its not opening. when your moving its like your truck, fresh air cools it down, but stop and temp rises. that or your cooling ports need flushed

 

[Coors]

Re: My first thread...merc overheating

Pull the hose, and check for good water from the impeller.

 

[Don S]

Re: My first thread...merc overheating

The shutters have nothing to do with your problem, they only slow down and prevent most of the water from a wave from getting to the engine.
If you are seeing those kinds of temps, and have good flow of water from the raw water pumps, then your manifolds or risers are plugged up.
Replace them.

 

[DockedPay]

Re: My first thread...merc overheating

OK..here's the update! (also see thread "Good or Bad Idea"). I didn't want to go taking apart engine components unless I could be sure the problem was not in the drive / impeller. As mentioned before the mechanic who actually installed the impeller (less than 2 hours on it) was at my boat and checked for water flow by pulling the hose at the thermostat. Said it seemed good! For some reason and symptoms I had, I just couldn't get past ruling out the drive/impeller.
So, I got some tubing and made extentions of my water supply lines and crossed them. SO, now my port o/d was cooling my starboard motor and vise versa. WHAT HAPPENED?....I ran both motors and now my starboard motor was the one that was overheating! Port motor ran like a top.
Therefore, I am sure the problem exists at the outdrive and I will have to pull the boat out. (........I will be calling the mechanic tomorrow!!..........). In fairness to the mechanic it could be a kinked hose but we'll see.
Anyway, I thought this might be a good tip for anyone else out there with overheating issue and wants to absolutely confirm or rule out the O/D. Note it obviously only applies to those with twin motors. Thanks to all who responded with suggestions. I will hopefully be up an running again soon. I'll let you know.

 

[wil7483]

Re: My first thread...merc overheating

I ended up pulling it and soaking it in a big tub of muratic acid. That ate a bunch of the rust and crud up. I then power washed it out and it's all good now.

I'm no expert but you're not fine now. You have a manifold which is about to fail. The clog in it was the 1st warning that it gave you that it needed to be replaced. The rust and crud is gone now so when it does fail on you it is going to send raw water into the engine and you will then have to spend a lot more money than you would've had to spend on a new manifold. Just my opinion. Maybe someone else will chime in and concur or disagree.

 

[Muqwump]

Re: My first thread...merc overheating

The rubber inside of these pumps dont last forever, even if you only use it for a few hours, they go bad. How long has it been sinse the pumps been rebuilt? i change mine out every season.

 

[DockedPay]

Re: My first thread...merc overheating

The impeller had around 2 hours on it. I had the boat hoisted out on the weekend ($100.00) and put a complete new impeller kit in the drive ($50.00). I then checked hoses for any obstructions while I was at it. Went to Walmart and bought the biggest plastic tote bin I could find ($10.00). Put my lower drive unit in the bin and filled it with water and made sure enough water was there to cover the intake holes. (didn't want to rely on muffs because pressure from hose may give false results). Ran the motor and HALLALUIA ran like a top!!.. Just got home from the marina. Boats back in and I took it for a good run...all's good!! (priceless!)...Thanks to all for the responses!!

P.S. I have talked to the mechanic. He had only put an impeller in and not a kit. I'm bringing him what I took out and will see what he does for me...