Need Help with Mercury 50 HP Motor

[CaptainJack]

Hoping someone can help me with this...I've had this motor in the shop the last month without any solutions.

I have a 4-Stroke Mercury 50 HP Motor.

I have noticed that the last few times I've taken the boat out it runs good going out but when I come back that I seem to have issues.

On the way back to shore I cannot get the boat to run more than 7 MPH on my GPS. With my throttle all the way down.

I've brought it into the shop twice, each time they have said that they have tested the motor and everything looks good. That I shouldn't have any problems.

Other observations:

When it's idleing the motor seems to shake a lot and many times it will shut off. I am also noticing noises that I haven't heard before during idleing: clanging noises like metal hit metal, a noise like when you have a hole in your muffler on the car).

I am thinking that my motor must be overheating...but I'm not sure.

Any help would be appreciated.

Thanks

[harvey lee]

I has some similar issues with a new 50 4 stroke. Wouldnt idle very good and at top end whatever that was the motor would kill and I had to pump up the primer bulb.

After 7 trips to the dealer, they replaced my fuel line and primer bulb, fuel pump, another pump along with another hose somewhere. Long story short, motor runs great now and they replaced all parts and lines for the fuel system.

Mine also had a clicking noise which I believe is the fuel pump pulsing.

Marineman will chime in when he sees this post and should have some very good suggestions for you along with a few others.

[Surface Tension]

Need more info.

Runs fine on the way out but can't get back any faster then 7mph. Are you shutting off the engine and then it acts up or are you making a loop?

Are the RPMs high or low when this happens?

What type of gas tank?

Are you seeing water coming from the tell-tale?

When an engine overheats you should notice a "smell".

Have you pulled the cover off and felt for high heat?

If your are overheating its damaging the engine and it shouldn't be run.

Have you checked the oil level in the lower unit?

[CaptainJack]

Quote:

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Need more info.

Runs fine on the way out but can't get back any faster then 7mph. Are you shutting off the engine and then it acts up or are you making a loop?

Example: I was out on the Saint Croix on Sunday. Went out at about 9:00 am. Get to a spot shut the motor off...fish for 45 min to 1 hour, move to another spot. It's running fine at this point. Do this for most of the day...Later around 4:00 pm, I decide to troll with the motor. Ran it for about 1 - 2 hours...noticed the noises. Around 8:00 pm decide to come in...start the motor fine...sounds a lot noisier then before, throttle all the way down, can't get the boat to go more then 7 MPH on GPS. Motor is spitting out water fine...good strong stream. I do notice that when I'm trolling about 2.5 to 3.0 MPH, the stream seems water coming out of the motor seems weaker, but if I increase speed to about 3.5 then the water stream is strong.

Are the RPMs high or low when this happens?

Don't know...my gauge does not work. But when I got it from the shop this is what they wrote on my Work Order:

1. Ran up motor, checked over, all systems check out OK.

2. Checked gearcase and it checks OK.

I do know that when the throttle is all the way down the motor sound strong...even though it's going slow, the motor sound powerful like no problem.

What type of gas tank?

I have a white/pale looking plastic Gas Tank. Now that I think about it...About 2 months ago, my aerator went out and I brought it in and they replaced the aerator. In the process, they said they had to remove the Gas Tank to get to the back. After this is when I started noticing this problem. I wonder if they didn't connect the gas tank back correctly?

Are you seeing water coming from the tell-tale?

Yep...Full Throttle it's coming out very strong. Trolling under 3.0 MPH not so much. Seems to be weaker...kind flies around almost like the wind is blowing the water.

When an engine overheats you should notice a "smell".

Have you pulled the cover off and felt for high heat?

I have checked for high heat...not really noticing anything.

But I did notice the first time this happened which was about two months ago...After I took the boat out of the water...I was smelling a Gas odor.

I have not noticed this smell lately though.

If your are overheating its damaging the engine and it shouldn't be run.

Have you checked the oil level in the lower unit?

The Oil level looks good and full, I always check before I go out.

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Here's some additional Info...

One other thing I notice that seems kind of odd is that, when I am about to return to shore...I have the motor tilted about even with the water level (Top of motor is flat), as I push the throttle forward and motor starts to power up, I notice the motor will slowly start to tilt down on it's own towards the water. (It's like the Prop Pulls further into the water?) I slow down, lift the motor up, start to go again and same thing happens.

Any help would be appreciated. As stated before, this boat has been in the shop twice and no one can solve it.

[Surface Tension]

"I do know that when the throttle is all the way down the motor sound strong...even though it's going slow, the motor sound powerful like no problem. "

I think you have a spun hub on the prop. Theres a rubber hub thats pressed into the prop. The rubber can get old or if you hit something it will slip inside the prop.

If your tell-tale is weak at idle its usually a sign its ready to go. I'd replace the impeller and have the prop looked at.

[LMITOUT]

Quote:

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One other thing I notice that seems kind of odd is that, when I am about to return to shore...I have the motor tilted about even with the water level (Top of motor is flat), as I push the throttle forward and motor starts to power up, I notice the motor will slowly start to tilt down on it's own towards the water. (It's like the Prop Pulls further into the water?) I slow down, lift the motor up, start to go again and same thing happens.

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There is a certain RPM the motor cannot exceed before it will trim the motor down. I believe it is 1000 RPM. Over that the motor will lower to ensure it's receiving the proper amount of water for cooling.

Next time out trim it up some and then slowly start to accelerate while watching the tach. It will probably start lowering the motor at the same RPM every time. Should be in the manual.

Even at full speed across the lake if you try to trim more than you should, the motor will automatically lower back to that maximum trim position.

[CaptainJack]

LMITOUT:

I have never noticed that before though. Even in the Spring, before this was happening. I could run this motor about 30-40 MPH and the motor just sat still(Where ever I had it whether higher or lower than normal). I have never seen the motor move down like it is doing now.

Thanks everyone for your thoughts and info.

I'm going to bring it in today after work and I'll have them check the Prop.

Hopefully that will solve it.

I'll post an update when I know something.

[LMITOUT]

The newer engines might be different than the 60 2-stroke....not sure. That engine would trim up as far as I wanted, but if I went over ~1000 RPM it would drop back automatically to that certain trim position that it was set at. It didn't go all the way down though.

Same thing when running across the lake. If the conditions were just right where the boat wasn't porpoising, I could keep trimming until I got to that point where the engine was over that magic position and it would drop back down a tad and that's as far as I could trim.

good luck.