1998 Mercury 40hp question

[gahunter706]

I have a 1998 mercury 40hp and when I was riding this morning it started making a whining noise. It would make the noise randomly for a few seconds at a time and then stop. Other than the whining, it ran like normal. Once we got to our hunting spot, the motor stayed in the water for a few hours and on the way back to the boat ramp it didn't make the noise any more. Any ideas what the noise could be? The only thing odd that I noticed was the prop would push in about 1/8", maybe even less. I never noticed this until today, but I have never really checked to see if the prop had any play in it. Any help will be appreciated.

 

[racerone]

Re: 1998 Mercury 40hp question

Model ? serial # ----2 stroke or 4 stroke ?

 

[gahunter706]

Re: 1998 Mercury 40hp question

It is a 2 stroke serial #0G66Z847

 

[joed]

Re: 1998 Mercury 40hp question

Could it have been the over temp/low oil alarm going off?

 

[carholme]

Re: 1998 Mercury 40hp question

Is the Z a 2 as there will be no letter after the first two?

If it is , that s/n comes up as:

MERCURY - ( 40 H.P. (1998 ))
Serial No: 0G662847 Model No: 1043412UD

Parts and Service Bulletin List for s/n 0G662847:

Search Results - Crowley Marine

Service manual you require is P/N: 90-852572. If you don't have one, see my PM to you in Notifications at the top of the page.

Gerry

 

[gahunter706]

Re: 1998 Mercury 40hp question

Could it have been the over temp/low oil alarm going off?

I don't think it was an alarm. Sometimes it would whine for 2 seconds and sometimes it would do it for 10 seconds.

Is the Z a 2 as there will be no letter after the first two?

If it is , that s/n comes up as:

MERCURY - ( 40 H.P. (1998 ))
Serial No: 0G662847 Model No: 1043412UD

Parts and Service Bulletin List for s/n 0G662847:

Search Results - Crowley Marine

Service manual you require is P/N: 90-852572. If you don't have one, see my PM to you in Notifications at the top of the page.

Gerry

Thanks for the service bulletin. I was thinking that it may have something to do with the gears, and according to the bulletin the pinion gear was a problem on this motor. I am going to run it again in the morning and see if it makes the noise any more.

 

[gahunter706]

Re: 1998 Mercury 40hp question

Could it have been the over temp/low oil alarm going off?

After running it this morning, I think it was the alarm that I heard. Yesterday I only heard the noise at full throttle and it sounded like it was coming from the motor, but the alarm in the console started going off at idle this morning so I think it was the alarm that I heard yesterday. I would think that the cold has something to do with it considering it was 10deg this morning, but it was high 30s yesterday when it was going off. What would cause the alarm to go off? It has plenty of oil and was peeing like normal. Just like yesterday, it only did it early in the morning and after the boat sat in the water for a few hours it wasn't going off.

 

[racerone]

Re: 1998 Mercury 40hp question

Cold freezing weather is tough on motors.----------------For one thing the lower unit should be submerged to keep it from freezing.----Possible ice in the waterpump must be allowed to thaw before start-up.Your local dealer may be able to give tips on cold weather operation.----If the impeller is more that 5 years old it likely needs a bew one.

 

[joed]

Re: 1998 Mercury 40hp question

Alarm at idle is likely the impeller. I had a similar issue and changed the impeller. No more problems. What happened is the impeller got stiff. At low RPM there was not enough flex to keep the seal and pump enough water. Higher RPM water flow was good.

 

[gahunter706]

Re: 1998 Mercury 40hp question

Cold freezing weather is tough on motors.----------------For one thing the lower unit should be submerged to keep it from freezing.----Possible ice in the waterpump must be allowed to thaw before start-up.Your local dealer may be able to give tips on cold weather operation.----If the impeller is more that 5 years old it likely needs a bew one.

I didn't think about letting it thaw once I put it in the water, I will definitely do that next time it gets this cold. I have only had the boat/motor for about 6 months so I don't have a clue if the impeller has ever been changed, but I think I will go ahead and change it. How difficult is it to change? I have done plenty of work on cars, but this is my first boat and the only work I have done on it is change the spark plugs and lower unit oil.

 

[gahunter706]

Re: 1998 Mercury 40hp question

Alarm at idle is likely the impeller. I had a similar issue and changed the impeller. No more problems. What happened is the impeller got stiff. At low RPM there was not enough flex to keep the seal and pump enough water. Higher RPM water flow was good.

Would that cause the alarm to go off as soon as the motor was started or would it take a few minutes? The motor idled for 3-4 minutes before it started beeping and it beeped 2 times for about a minute each time.

 

[joed]

Re: 1998 Mercury 40hp question

Not sure about that particular motor but beeping alarm is oil related and constant is heat related on most mariners. The alarm should beep for a second or two when the ignition is first turned on as a test.

 

[tyst67]

Re: 1998 Mercury 40hp question

I know these motors well and it sounds like to me it was the water pressure alarm. Make sure the motor is pissing properly. it may freeze up in the cold temperature. check the **** hole to see if it is plugged or if it has dirt in it. Also check your water impeller as the paddles may be in bad shape. DO NOT RUN when you hear this alarm cause you WILL melt it down!

 

[BatDaddy1887]

Re: 1998 Mercury 40hp question

...there are many good vids on YT. Here is one that will show you how to change the impeller. Just don't forget the bolt under the trim tab!

 

[gahunter706]

Re: 1998 Mercury 40hp question

I know these motors well and it sounds like to me it was the water pressure alarm. Make sure the motor is pissing properly. it may freeze up in the cold temperature. check the **** hole to see if it is plugged or if it has dirt in it. Also check your water impeller as the paddles may be in bad shape. DO NOT RUN when you hear this alarm cause you WILL melt it down!

That makes sense. Every time the alarm went off, it was below freezing so there is a good chance that there was ice in the water tube. The last day I ran it, which was almost a month ago, the tip of the pee hole was completely covered in ice and no water was flowing. We noticed that and got it unstopped before the alarm went off, and then my control box broke :frusty: I got a new set of controls on it last weekend and plan on running it Friday night.