5.7 merc alarm going off while running.

[dmurph]

Hello everyone ,
New to the forum , live in Vancouver Canada and have a new to me 2007 trophy 2359 pilot house sport fisher which my wife and I salmon fish on here on the west coast. The boat fuel system had water in it when we purchased the boat which we are still dealing with . I have pumped the fuel tank , changed the filter and added a racor and had the carb cleaned . I think the water was getting in through the perko gas cap which had no rubber gasket and I had heard the gas cap was recalled in the 07 trophy. There is still some water but the boat has been running great i believe . The motor is a 5.7 tko carb with alpha 1 drive with 170 hrs. I have been running at 3600 to 3800 hundred rpms and average about 28 mph in the ocean . Does this seem right the motor seems happy at 3800 rpm is that a little to much to cruise at? Last day out the alarm which comes on when the key is in the ignition staye3d on while running , it kind of seemed intermittent and everything seemed normal , oil pressure was between 40 or 50 and temp was around 175 . Do you think the alarm is faulty or what could it possibly indicate ? Thanks for the help in advance.

 

[fossill]

Re: 5.7 merc alarm going off while running.

Engine overheat, low oil pressure, or low outdrive fluid

 

[jmarty10]

Re: 5.7 merc alarm going off while running.

Yep - you narrowed it down to the last one. Check you gear lube level, you may have a monitor mounted next to the engine. If no oil in there you mayhave narrowd it down. As far as performance, lots of factors that affect performance. Prop, weight, conditions etc... Make sure the boat is propped correctly for your type of boat and engine.

 

[dingdongs]

Re: 5.7 merc alarm going off while running.

pull one of the sets of wires at a time if its constantly going off so long as you know for definite your not low on fluids and see which one stops it.could be a faulty sender too

 

[dmurph]

Re: 5.7 merc alarm going off while running.

Hey thanks for the replies everyone. Went to the boat today the drive fluid was a little below the add line in the reservoir . Topped it up to the correct level and went for a rip in the boat. The temp gauge would read just over 175 at operating , once warm at idle and creep upwards to 190 when going up onto plane. Alarm started to sound off and on when I WOULD HIT 3000 RPM, alarm would go off for a while after boat was on plane then come on and off again at random. The temp would read 190 just after getting on plane. Had topped up engine oil also and oil pressure was between 50 and 60 on the gauge. Bought a digital temp gauge for $99 and was getting a reading of 168 around what I believe to be the thermostat , got much lower on the top of the intakes , and the highest reading I had was the backside of the manifolds near the topside of the motor which read 189. After driving for a while and the boats gauge reading 190 ish I could easily hold my hand on the top of the intakes or exchangers so not hot to the touch anywhere. Do you think I have a faulty sender , bad thermostat, or maybe does the alarm sound from the drive oil being low and has not reset . The boat was running fine for several weeks now before this happened, and the day it did happen I drove for 20 min to get back to the dock, as I thought it was just a faulty alarm, my point is if I drove for that long with the alarm on I would think the you be signs of major damage if the alarm was actually indicating an overheat. I am new to this and want to learn , what do you guys think . Would love to solve this and be on the water in a salmon derby for the weekend. All mechanics are booked. Please help.

 

[John_S]

Re: 5.7 merc alarm going off while running.

190 is too high. The temp sender for the gauge and the one from the alarm are different. Unlikely to be having an issue with both at the same time. The oil res being just below the add line did not cause the alarm. You need to identify your drive and cooling system so people can help with the diagnoisis.

 

[dmurph]

Re: 5.7 merc alarm going off while running.

The drive is a alpha 1 with fresh water cooling. Also keep in mind the boat gauge read 190 but the digital gauge never read that high. thanks

 

[John_S]

Re: 5.7 merc alarm going off while running.

The drive is a alpha 1 with fresh water cooling. Also keep in mind the boat gauge read 190 but the digital gauge never read that high. thanks

Your digital gauge was measuring the outside housing temp, correct? If you want you can remove both sensors and test them in a bucket of hot water to elliminate any doubt.

Myself, have a raw water cooled 5.7L and will only be able to minimally assist with ideas.

- When was the last time alpha drive impeller was changed? If no record, best to change it.

- Heat exchanger. I'd suspect that there is some type of regular cleaning or back flushing that needs to be performed.

Others with much more expierence with your cooling system will be able to assist in a more detailed approach/diagnoisis.

 

[Don S]

Re: 5.7 merc alarm going off while running.

2007 trophy 2359 ........ The motor is a 5.7 tko carb with alpha 1 drive with 170 hrs.

1. Do you have a Mercruiser serial number for your engine?
2. You have an Alpha I Gen II, not just an Alpha I, there is a difference.
3. Do you have a full cooling system, or a half system?
4. Is your heat exchanger OEM or aftermarket?
5. Do you have an engine driven raw water pump?

If you aren't sure about questions 3,4,and 5, post some pictures of your engine.

 

[dmurph]

Re: 5.7 merc alarm going off while running.

Thanks for the replies. Had the local shop sqeeze the boat in for work today. The mechanic was confident that the impeller would need to be changed and that this would fix the problem. Not the case cahanged it out today altough it was not that bad but was a bit worn out . Alarm still going off but very sperratic. Thinking a sender could be the issue will see tomorrow as the sea trial was at the end of the work day. Don S . the serial number is 1a044196 believe this is what is written in my manual could double check on the actual motor tomorrow but I think that sounds correct. Would need to take photo to answer yout other questions. What do you guys think , now has new impeller does not seem to be overheating both risers cool getting a reading of 170 at the base of the thermostat housing with the digital temp gun. Gauge does still go between 175 and 190 when running. Noramal temp since I have owned the boat has been 175 on the gauge and now the alarm comes on around 180 or so .

 

[John_S]

Re: 5.7 merc alarm going off while running.

What do you guys think , now has new impeller does not seem to be overheating both risers cool getting a reading of 170 at the base of the thermostat housing with the digital temp gun. Gauge does still go between 175 and 190 when running. Noramal temp since I have owned the boat has been 175 on the gauge and now the alarm comes on around 180 or so .

I still think you have a problem that may get worse. What did the shop say?

 

[fossill]

Re: 5.7 merc alarm going off while running.

I don't know at what temp the alarm is calibrated to sound. I'd change the alarm sending unit. Easy to do and not expensive.
In saltwater applications you want to run 160 or cooler as salt water exposed to higher temps cruds things up. I'd change the thermostat to lowest available 160 or 140 if possible.
As an aside overheating under prolonged high load conditions usually points to clogged/restricted heat exchangers or faulty head gaskets and or cracked head from my experience. I doubt that's your problem though with the info you've given.

 

[dmurph]

Re: 5.7 merc alarm going off while running.

Seems like a loose connection to one of the sending units was the problem. Unplugged the units and replugged them in and no issues now.

 

[achris]

Re: 5.7 merc alarm going off while running.

Not possible. The alarm switches are N.O., so if there was a loose connection you would have the opposite problem, the alarm not sounding. Your problem is/was something else. Test each part of the circuit by disconnecting each sender and grounding the wire. The alarm needs to sound.

Chris.......

 

[Pete104]

Re: 5.7 merc alarm going off while running.

chris, what's N.O.?

 

[Don S]

Re: 5.7 merc alarm going off while running.

N.O. stands for Normally Open in electrical terms. N.C. stands for Normally Closed.

 

[Pongman]

It can’t be low oil pressure or something like that? Pressure is 42, that’s low.

 

[GA_Boater]

It can’t be low oil pressure or something like that? Pressure is 42, that’s low.

This problem was resolved one way or the other 8 years ago.

Closed.