Overheat - MPH Mercury performance

[bucky]

Looking for insight from the community. I have new ('11) Aqua Patio tri toon with 115 Merc. I have 2 issues and wondering if they can be related. First, The speed has been lacking. In the 18-23 mph range (gps). Reading other posts, I changed out the prop to a 14R13. I'm not a speed demon, but did not notice a big difference. Second, the channel to my slip is shallow. 2-3 feet. I have had the warning alarm go off a couple times. I understand that I'm overheating and I need to trim up. I'm learning. Its a challenge because with any acceleration, the motor trims downs automatically. To trim more than 1/2 up, I have to almost idle in. Within the channel, other boats & pontoons are passing me by... The motor has to be 3/4 up to avoid the alarms/ motor shutting down.

I assume that trim function is a safety feature. Is that common ? Could the motor be mounted at the incorrect height ? Would that add to the overheat issue as well as the overall MPH performance. When on the open lake, I have been trying trim up to see if that impacts performance. Same result with this trim function. Since, I swapped out the prop out, I'm trying to determine if I should have anything else checked out.

Any comments would be appreciated. Thanks !

[cwag911]

The trim should stay where you set it. There could be a problem with the trim pump or checkvalves inside. I would have the dealer look at it. I don't know if you have a trailer but if you do, raise the motor up some and then see if you can push it back down.

[Bryden24shp]

I have had the warning alarm go off a couple times. I understand that I'm overheating and I need to trim up. I'm learning. Its a challenge because with any acceleration, the motor trims downs automatically. To trim more than 1/2 up, I have to almost idle in. Within the channel, other boats & pontoons are passing me by... The motor has to be 3/4 up to avoid the alarms/ motor shutting down.

This makes no sense at all! I think you need to get your dealer involved. He can hook it up to do a diagnostics scan, the EMM should have a code in it for the alarms. Should be under warranty, correct?

Hope you find out its something simple to fix. Let us know what you find out!
Bryan

[gramps]

Well your speed should be a lot better than what your getting. What are your rpm's? Mercury is sending our their Service manager to check out my motor next week as I have had a lot of problems.
I have changed 3 props with absolutely no difference in rpm's or speed, so I know that something is wrong besides all the other problems that I am experiencing.
Take the boat to the dealer and let them correct it.

[GregF]

You should look into a water pressure gauge. It will give you instant feedback about your cooling system. Simply being in shallow water should not cause overheating if you are not plowing mud. Is it peeing?

[bucky]

Being a new boater... i had the boat pulled and took back to the dealer after first overheat. They ran the motor through the diagnostics check. No harm to motor on the alarm incident. i was told because the channel was shallow 2 to 3 ft, I was getting dirty water. Picking up silt from bottom going through channel. by trimming up i get cleaner water. i insure its always peeing when going though the shallows. tilting way up seems to address the overheat.

I have the sea star steering package. i assumed that the tilt adjustment as i accelerated, was part of that set up. You hear the motor adjust if you tilt up with speed. Its not a failure to hold the motor position. Again, I assumed it was a safety feature.

At the same time, they switched out the prop to address the speed. the rpm's are in the 5000-6000. The motor feels like it is laboring. I may just have to get the dealer out on the lake to see first hand.

thanks for the comments

[GregF]

You should really have it trimmed down when you accelerate. If it is trimmed up you are pushing the stern down and making it plow. You are actually drawing more water than you would at idle speed.
I always get a laugh out of people around here at 2500 RPM or so trying to get through a shallow spot with their motor trimmed way up.
If you are trying to jump up and get up on top in shallow water, trim it all the way down and ride the trim up to level as the boat gets over the bow wave. It is a trick best learned in deeper water. Once you figure it out you can get going from a pretty small hole.

[Bryden24shp]

Bucky, does that motor have a low water pickup? I'm not sure if the 115's do or don't. If it does, you can tell by looking at the nosecone, on the lower unit. It should have a hole in the front of it, with a screen in it. You may be getting silt through that, if you have it. If you do, take some electrical tape and plug it off. It should stay on long enough to see if the condition goes away. The motor will be fine as long as the upper water vents, in the side of the lower unit are under water.
Just a suggestion, if you have a LWPU.

What do you think, GregF? Will it have one?
Bryan

[GregF]

I don't think it is standard on a merc 115. My neighbor doesn't have it on his.

My Yamaha seems to have better tilted out performance than my old Merc 60. It pumps more water with the prop chopping water

[LTB Racing]

The 115's do not have the low water pick ups....and yes the trim will bleed down under power if its trimmed to high and into the trailering posistion...Somethings a miss here....how many times have you had the alarm? is it always in the same area that you overheat? Never anywhere else?
Is this a 115 4Stroke?