# Engine alarm at low trolling speed



## Murphy's Law (May 27, 2014)

Last few times out I have had my engine alarm go on when trolling at low speeds. I have a Mercury 4 stroke 50hp. When I speed up a bit it eventually goes off. Could the primer bulb be the problem or is it more likely a water pump going bad??


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## kmb411 (Feb 24, 2005)

My two guess is the impeller may be going bad (normally replaced every 2-3 years) , or the intakes could be clogged/ have debris. Those are the easy first two things to check.


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## Murphy's Law (May 27, 2014)

Will check those! Thanks!!!


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## EyeCatchEm (Jan 6, 2014)

I have the same problem right now with my 200hp Suzuki 2 stroke. I'm beginning to think water pump. I flushed my engine which should be your first thing. Swapped thermostats, now on to water pump again.


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## bountyhunter (Apr 28, 2004)

EyeCatchEm said:


> I have the same problem right now with my 200hp Suzuki 2 stroke. I'm beginning to think water pump. I flushed my engine which should be your first thing. Swapped thermostats, now on to water pump again.


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## bountyhunter (Apr 28, 2004)

I though the beeps came in code that way you new where to look for the problem.


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## blackxpress (Nov 20, 2009)

What does the alarm sound like? Is it a beep, beep, beep, beep or a beeeeeeeeeeep? If the latter that means, "Shut me down and don't start me again until I'm fixed." I'm going to take a wild guess and say your problem is low water pressure but that's just a guess.


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## Murphy's Law (May 27, 2014)

It is a continuous beep not broken. I have spoken to 2 outboard mechanics today and they agree it sounds like water pump needs a new impeller.


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## UFM82 (Apr 6, 2004)

If you are getting an overheat condition at speeds above idle but it seems to go away when you speed up that is your engine telling you to change the water pump. As has been mentioned before, the rubber vanes take a set over time and lose their ability to pump water. An outboard sitting still in neutral idling generates very little heat but put the load of pushing a boat at that same RPM and it builds up a good deal of heat. The water flow generated by a weak pump simply isn't enough to keep it cool. All you have at that speed is the water pump. However, speed up and you get more ram-force water pressure as the water is forced into the intake in the lower unit. That's why the engine cools down once you speed up. 
However, while some think just a new impeller is the fix for this issue and in many cases it is. BUT, not always. In fact, there is an additional item that you may not think about. Since impellers run in SS shells in the water pump some never replace the housing. Also, the impeller must seal well on the bottom of the housing. That means to fully do the job and repair the engine completely you should replace the impeller and both the upper and lower housings. When you replace the impeller you are already right there so it's no more work. Also, the upper oil seal for the driveshaft is part of the lower water pump housing on most outboards and it's a good idea to replace that occasionally as well. 
The poster with the Suzuki will most likely remedy the condition he has by replacing all three components as listed. My Merc 150 is very particular about its water pump and it tells me it is unhappy by overheating at RPMs between 2500 and 3500 at first. If I let it got longer the range grows. I've not let it go much further as I think $80 for all the parts is not too much to pay to prevent buying a new outboard. (A new 150 is what, 12K?) It takes about an hour to change the entire thing and you get to lube the driveshaft splines and shifter rod splines at the same time. Who could ask for more?


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## Murphy's Law (May 27, 2014)

Thanks ufm82!! Really appreciate the help!! I will have the water pump replaced this weekend.


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