While on Lake of the Woods the other day, my warning horn came on, the continuous alert, I shut it down, checked for water flow, plenty, checked oil, plenty, other problem could be oil pump the book says. I had 6 miles to go to the landing so I poured 2 quarts of oil into my gas tank and went for it, Horn started up when I fired up the engine and went away in about a few seconds of power, when I slowed down to an idle at the landing it came back on. Any body out their have a similar experience? Maybe just a faulty sensor? anyway I am going to bring it in tomorow and hopefully the local merc dealer mechanics can figure it out, way too expensive a motor to gamble on. I was safe pouring oil into the gas wasn't I? except for maybe fouling plugs I know for sure that the engine was getting oil right?

Had the exact issue with my 225 Opti. Have them change out the thermostats.
My stats looked fine but were bad. Do you have Smartcraft? You should have seen high water temperature (170 degrees)
When you throttle up, you create enough water pressure to force the faulty stat open but at idle there is not quite enough pressure.

Well its fixed, impeller replacement, 716 hours on the engine, they claim when I was traveling at speed their was enough water pressure to get by, but not at idle, you sure could have fooled me because I thought I had quite a stream of water showing? Oh well out on the lake tomorow for my own personal on the water test!

Good to here Dave, hope all is OK. You have put some hours on that motor! Do you have a Lund Pro Guide?

Well its fixed, impeller replacement, 716 hours on the engine, they claim when I was traveling at speed their was enough water pressure to get by, but not at idle, you sure could have fooled me because I thought I had quite a stream of water showing? Oh well out on the lake tomorow for my own personal on the water test!


Dave,
How often do you change the impeller? I have a 150 Opti and do mine every 3 years. I think that is what Merc recommends, although I do know people that have gone 5 years.

Even if the engine is not used often, the impeller gets "cupped" in its housing and doesn't do as good a job pumping water through the engine, so age is a factor in impeller deterioration as well as usage hours.

You may know all this, just mentioning if FYI.

Yes I have a pro guide, love it! its a 2007, bought it used from a guy on the Lund Pro staff, and I spend about every bit of time I have on the water fishing, matter of fact I am off for a day of fishing right now!

WOW!! Thats alot of hours on that engine in two years...

I wish I could get my 04 175 opti to last more than a few hours without the temp warning sounding. I replaced the impellar 3 times so far and the thermostats this spring( with impellar) and have the same problem again. It overtemps at low rpms. I have 182 hours on this motor, about 35 hours on it since I replaced the impellar and thermostats this spring. The dealer keeps repeating the manufactures recommend every year replacing the impellar. Bull Sheet!!! I am getting very frustrated with this motor. I am thinking of selling the whole rig. It is even more frustrating to here that other people are getting 400-500 hours on an impellar. My boat spends most of the summer on a boat lift so not to many sandy landings and I am very carefull about running in shallow water to prevent picking up sand. I think I have a lemmon here.

Well here is the report, drove about 45 miles north of me on a beautiful fall day, launched the rig, fired it up, and within 5 seconds the horn went off! I went wild! Limped out a block with my kicker, caught some walleyes and made a beeline back to the dealer in Walker, worked hard to keep my temper under control, they put it on the computer and found a chaffed wire, gooped and taped it up and said I am good to go, we'll see, tomorows trip will be on Leech Lake a block away from my house, report to follow!

Dave,
Did they look at the water filter/seperator under the cowl? I understand those can be tempermental, too.
HRG

No, they did not, I also called mercury to check on their warrantys, impellers are considered maintenance problems, so beware! just because your motor is under 3 years old and under warranty, things are not as they seem.

Don't you just love the "parts replacement" type trouble shooting some repair shops do? They could have at least fired it up and tried it to see if the impellar fixed it. I just picked up a older 20 ft tiller with a 115hp motor, but a Lund Pro Guide was on my short list. Is it possible to fish with the 175?(backtroll, foward troll, etc.) Or is a kicker a must?

Yes it is a very fishable motor, forwards and reverse, I have electrics front and back and a kicker . I use them all, depending on the conditions, but if their is much wind the big merc is just fine. It is truly amazing how far outboards have come, remember trying to troll with 25 to 35 hp motors in the late 70's? how they would buck and cough and load up.

just went through the same problem with my opti had it to five differant dealers in metro area and never got the problem fixed called Lybacks in Isle last nite they led me through some tests to do here at home and it reacted just like they said it could, so pulled it up to them this morning and in a couple of hours they had it all taken care of, the filter under the left cowl was plugged everyone else said it was the thermostats at $70 a piece for the thermostats good savings. the screen is a tube that all the cooling water has to go through highly recommend Lyback for any kind of work top notch the only place my engine will be worked on they also adjusted throttle linkage and a couple of other things, others had over looked

my vote alos goes to lyback's they have worked on my opti a few different times. found the trouble and didn't rob me in the process. dave, i forgot to tell you to give them a call and see what eddie thought, he has a really good opti mechanic.

what kind of pressure did you guys have going wide open. I have about 1 psi at idle and 12-14 psi wot. I only have problems at slow speeds.