XR6 150 Overheating

[Charlie Carter]

Ok, I warned you about my newbie questions. Here is the first.



When I bought my Nitro the previous owner told me that the motor only had two alarms, a steady horn for overherating and and intermittent horn for low oil pressure. Working with the assumption that what he told me is correct, I have an overheating issue.



I can start the motor, either on muffs or on the water. After several minutes the thermostat opens and it looks like a cow whizzing on a flat rock. Can't tell you the water pressure, the gauge is bad and will be replaced next week. It will idle, in neutral at 800 RMP, like this as long as you like (20 minutes - no sense wasting fuel).



Put it in gear and keep the RPM's between 800 & 1000, with a Hotfoot, and after about 10 minutes I get the overheat alarm. The time varies depending on how long I have had the motor off, but has never been more than 12 minutes.



I haven't had a chance to try it at a faster RPM setting yet. My closest lake is an "Idle Speed Only" lake. I need to get this resolved soon. I am having a Humminbird 1198 put on next week and the speed the motor overheats at is the recommended speed for the side imaging.

 

[Jim clear]

I also have a 150 xr6. Its a 2005, bought it last summer. First time out it was ok until about 15 min then the overheat alarm went off. Ok at idle and slow speed. These mercs dont piss until the temp gets to 143 deg and the thermostats open. Since it was new to me, I changed the impellar. both thermostats and the poppit valve. Found seal on impellar housing was almost gone. Have had no issues since. But yes the constant alarm is the water temp. Also most certainly get your pressure guage fixed. Mine runs at about 10 to 11 psi at idle and 15 to 18 at high rpms. This will also help you when your trimming your motor to make sure your not to high. Drop in water pressure will tell you this. All three items are pretty cheap and easy to do. The hardest part is removing the lower cowl to get at the poppit valve. If you need any help let me know.

 

[Charlie Carter]

The previous owner told me he had recently changed the impeller. Idle in neutral is ok but in gear is when it overheats. I was told that having the motor trimmed down and tucked under the boat would cause overheating so today I kept it at the neutral or in a more up trim, but not enough to water starve it. I'm taking it to the shop on Monday and the mechanic has a good reputation. I'm just trying to get a handle on what I am looking at. From what others have told me, once I get the side imaging, I will spend most of my just idling around amazed and what I have been missing for all these years.

 

[Bruce Freeman]

Check the oil tank under the engine cover, it should be full to the top. I had an issue with mine where the oil pick-up tube in the main oil tank had some alge on it and waht I thought was an over heating alarm was the low oil alarm for the the engine oil tank.

Juat a thought.

BF

 

[Dan J.]

As long as the lower unit is submerged you should be drawing and pumping water through a properly working unit. (On muffs, trim motor perpendicular to ground.) First question I have, is there any low water pickups on the L/U? (Water intake holes in bullet nose of L/U.) If so, if they are not taped over while ran on muffs you'll be feeding air into the impeller and I would suggest without hesitation to replce the impeller, gasket and housing before use on the water. Removal and a visual check of the T-stats and poppit would be advised next. A little mud residue on them in a hot powerhead can concrete shut your 'stats and poppit. Bruce brings up an important thing to watch for. The older the motor the higher the chance of a blocked screen setting off the sensor and worse, starving the engine. Algae build up can eventually close it. Along that line, make sure your saddle tank on the head is completely full of oil. With cap off, let engine fill saddle tank up while running then re-install cap with 1/8" or less of air left to go. You want that tank completely full. One last thing, (hopefully very extreme) and it can be a gut wrencher, pull each plug and look for one (or more) that are sparklingly clean. A small cylinder crack will steam clean that plug and give a tell that a serious issue is looming. The last item I mentioned is a longshot, so don't get too worried. The beauty of your XR6 is that it is one solid built unit on a proven design and easier to figure out than many of the newer designs. Good luck!

 

[Charlie Carter]

Dan - Nothing taped up. I had the compression checked before I bought it and it was 120 across the board. The mechanic didn't say anything to indicate a cylinder crack. Oil is full and appears to pick up fine.

 

[joseph currier]

charlie,

this is a trouble shooting problem. you need to connect the dots.

the question dan asked you first is weather or not you have low water pickups on you lower unit, they would be located near the nose cone, if you do you must tape them up

to run on muffs properly. if you dont have low water pickups the next step is thermostats, poppit, and yes impeller and houseing and all seals&gaskets.(even if the prior owner is the pope and states he did it) nothing says it was done correctly.

these things must be ruled out before you can speculate futher period. and they are the cheapest solution.

next check your pick up screens for debris make sure they are clean.

after all these issues are ruled out, look under the motor cowling for any water

coming out of any gasket in and around the block this should rule out head gasket.

next run your engine on a auxillery tank with gas premixed 50/1 this should help rule out weather not getting oil is even an issue, if no overheats with premix gas

them look at the oil delivery system.

but with all due respect charlie sometimes it just works out better if we just bring it to a pro and pay the piper(almost always cost less in the long run) unless you have the school and background in marine mechanics or feel you can fake it.

i've seen hundreds of guys who were shade tree mecanics do more damage than good.

at any rate good luck remeber it's connect the dots you cant move on to one thing without confirming the first.

 

[TROY WAINRIGHT3]

Charlie,are you getting alot of smoke from the exhaust when its runing?Should be pretty thick cloud of smoke if not its probably an oiling problem.Had my 2004 xr6 rebuilt lastyear do to catastrophic oil failure.In short that means merc put a crappy poly gear on the crank of that motor with a metal gear on the oil pump.Guess whats gonna go first.Try adding oil directly to the tank like your double oiling for break in.If the alarm doesnt sound ya know the problem and can disconnect all that oiling crap.Yes its a hassle but i feel a lot more confident in my motor.Good luck and let us know.

 

[joseph currier]

charlie,

troy seems to have a need to mix direct oil into the gas?on your 43 gal tank? after you find the problem your stuck with premix in your boats tank? makes no sense.

as i already said use a portable tank hook it up to the motors fuel line mix it 50/1

and see if you still overheat? if so have a pro figure it out.

who want's a mickey mouse fix on their new boat?

no disrespect intended to troy but expermentation done by someone who has no training is a terible idea.

if you are not confident in your mechanical you will be much happier bringing it to a qualified merc mechanic.

just my two cents.

 

[TROY WAINRIGHT3]

Sorry joe,didnt see the portable tank idea.

 

[Charlie Carter]

If it was an oil issue, wouldn't the oil alarm go off? (Stupid question #2). There is a cloud of smoke when I start it and I can smell the odor of oil when it is running. There isn't a "cloud" of smoke while it is running though, either idling in neutral or in gear.



I am taking it to the shop this morning. From all of the posts here, I have decided it is beyond my comfort level, at least at this point. I'll let you know what it turns out to be. Thanks everyone

 

[Charlie Carter]

Preliminary report from my mechanic is that one of the thermostats was working, one wasn't. I'm having him replace both since he is already there. More to follow....



And the bad thermostat was the problem.:lol: I spent over an hour idling around the lake getting familiar with my Humminbird SI and never had the first problem with overheating.



Thanks to everyone for their help and suggestions.