Alarm driving me crazy...

[clinche]

Re: Alarm driving me crazy...

JerryJerry has you on the right track. As you get the boat into higher RPM's your boat needs more water volume to regulate the extra heat. YOU have a restriction keeping that extra volume from being achieved. Once you bring the RPM's back down, you are back within the range of heat transfer. That's why your engine cools back down.
Look for any pieces of old impeller. It only takes a little bit of blockage to screw up the whole system. If you can't find anything in the water passages, look to the risers.

can u please guide me from where to start checking the water passages so i make sure im doin everythin right?

thanks

 

[clinche]

Re: Alarm driving me crazy...

hey just throwing in my 2 cents, when i baught my boat it needed a new impellor, when i took it all apart i noticed a few of the impellor blades that broke off fell down into the inlet on the outdrive, easy to check, just take off the inlet covers and make sure its not blocked there. never know could solve all your problems...

where can i find the inlet covers?

 

[Bt Doctur]

Re: Alarm driving me crazy...

The inlets are where you put the muffs for flushing.
You say you replaced the impeller with a full kit? or just the impeller.
Had one similiar that turned out to be the pump base gasket. At hi speed the water pump housing is in the exaust flow above the water level and was sucking hot gas under the pump base.Only way i found it was to drop the lower,and put the muffs on it. sprayed out from under the base gasket.

 

[clinche]

Re: Alarm driving me crazy...

The inlets are where you put the muffs for flushing.
You say you replaced the impeller with a full kit? or just the impeller.
Had one similiar that turned out to be the pump base gasket. At hi speed the water pump housing is in the exaust flow above the water level and was sucking hot gas under the pump base.Only way i found it was to drop the lower,and put the muffs on it. sprayed out from under the base gasket.

ohh ok..the inlets look clean but i am only looking from the outside..To be quite honest i am not 100% sure if the mechanic replaced the housing. i am sure that impeller was changed and a couple of gaskets and i recall us finding a white platic tube (about 2inch tall) which was in bad shape..mechanic said that the lower unit had overheated and he just threw away this part! the lower unit is an alpha gen 2..

 

[clinche]

Re: Alarm driving me crazy...

still no time to start checking the hose pipes for any blockages.

Today i started the motor on the muffs. engine started right away considering the last time it ran was 3 weeks ago. Now i noticed that the water coming out from one side of the outdrive is too hot to touch (close to boiling) however the other side is just warm.

Quick question guys:

Is this a symptom of one riser running hotter than the other and that there is a blockage of water somewhere in the system?

any input will be greatly appreciated.

 

[clinche]

Re: Alarm driving me crazy...

anyone?

 

[Don S]

Re: Alarm driving me crazy...

What engine do you have? Volvo? Mercruiser? Model or SN's

 

[clinche]

Re: Alarm driving me crazy...

What engine do you have? Volvo? Mercruiser? Model or SN's

mercruiser 5.7ltr V8 carb S/N L-376357 and alpha 1 gen 2 drive

 

[intrepidvoyager]

Re: Alarm driving me crazy...

notwithstanding any cooling system issues you may have if an ir thermometer pointed at the thermo housing is reading lower than the alarm temp switch closing temp ....check yours ...should be 185 to 195 ... then you have a bad sensor/switch ..OR.... make sure a previous owner did not mess around with the wiring ........ these switches work on resistance so any ground anywhere in the circuit will work the alarm.

 

[intrepidvoyager]

Re: Alarm driving me crazy...

just remembered ...had an issue where the alarm test module was acting up .... thats the curcuit that will activate the alarm as when you turn the ignition to the run postion and don't start the engine ...... also make sure the previous owner did not add a low oil pressure, low fuel etc switch to the curcuit.

So to confirm its a sensor/switch or not when the alarm sounds and the engine temp is reading normal on the IR thermo pull the wire off the sender ....if the alarm stops its the sender ..... if not probably something in the harness or the module is grounding

 

[intrepidvoyager]

Re: Alarm driving me crazy...

now to test on the hard whether you have a blockage on one side vs the other ..or before the manifold/risers ... hook a hose up to the ok side manifold inlet and run water thru the manifold/riser ..... put a bin under the leg ... make a mark half way up the bin .... set your stop watch ...and run the water full pressure ..... time how long it takes to fill the bin to the mark. ...... then do the same for the suspect manifold/riser side and note the diff ....if there is a diff well got to be in the manifold/riser ...... if not its in the delivery of water to the bad/hot side .

 

[clinche]

Re: Alarm driving me crazy...

now to test on the hard whether you have a blockage on one side vs the other ..or before the manifold/risers ... hook a hose up to the ok side manifold inlet and run water thru the manifold/riser ..... put a bin under the leg ... make a mark half way up the bin .... set your stop watch ...and run the water full pressure ..... time how long it takes to fill the bin to the mark. ...... then do the same for the suspect manifold/riser side and note the diff ....if there is a diff well got to be in the manifold/riser ...... if not its in the delivery of water to the bad/hot side .

that is some useful info. i will test this out next weekend and will post the outcome..it is highly unlikely that their is a blockage in the risers or manifolds as they were replaced this year..but still worth a try...

Thanks for the input..

 

[intrepidvoyager]

Re: Alarm driving me crazy...

OK ...great you have a ir thermometer ....handy tool in this situation ..... however 180 is too high for any riser temp ..... you should be able to put your hand on the riser at any rpm and not get burned. You may have, like so many engine issues, a couple of things going on here. The differential in riser temp indicates a reduced flow on one side but the fact that both are over heating is curious taking into account the ir reading at the thermo ...Were all the temp readings taken at the same time ? .... if so then both risers are suspect .....just to confirm ...you have done the impellor right ? ...did you check that there is no debris on the raw water side of the ps cooler or oil cooler if you have one ? ...... think you mentioned you did the thermostat ... even new thermos can be faulty but you can easily check with your ir therm.

Did you check that the raw water pump drive belt is tight and is not slipping.

Check for blockage in the leg raw water inlet.

you mentioned that the risers were done fairly recently ..... with all the above in mind I am beginning to suspect that you have the wrong riser gaskets installed ...or incorrectly installed .... easy to check but before you do ...if you can backwash the manifolds with hose ...if you can and see if any crud comes out ..... keep posting and someone will hit the nail on the head

 

[intrepidvoyager]

Re: Alarm driving me crazy...

oops ...forgot you are taking these temp readings on the hard where you cannot duplicate the cooling flow rate of the boat being in the water ...so once you have satisfied yourself re the previous mentioned issues you will have to get the boat in the water .... then check temps . you might be interested in the following re flow rates , etc

Warm versus cold manifold refers to the temperature of the cooling water that is introduced into the exhaust manifolds on a marine cooling system. This specific system feature can apply to raw water (also known as open cooling) systems as well as Fresh Water (also known as closed cooling) systems. For the purpose of this article we will be primarily detailing the raw water cooling systems. To read more about 1/2 versus full closed cooling systems, select this link.

The standard raw water cooling system operates via a pressure balance. The easiest way to think about these systems is that you have a circuit of coolant being circulated through the engine via the engine circulating pump. There is also a supply pump that introduces cooling water into this circulation loop, depending on the position of the thermostat and amount of coolant being allowed to exit the system. For example the circulating pump on a standard small V8 GM based engine will flow approximately 50 gpm through the engine. The typical raw water supply pump inside the Alpha sterndrive is capable of flowing about 18 - 20 gpm depending on the gear ratio and restriction the system experiences. A standard 300 Hp small V8 engine dissipates approximately 300,000 Btu/Hr of heat into the coolant. To maintain a thermostat temperature of 160 degree F at wide open throttle this engine would need a pump to flow about 8 gallons per minute (GPM) of 70 degree F water into the system to maintain this engine temperature. Since the Alpha raw water pump can flow 18-20 GPM there is significant bypass (excess) water supplied, which therefore has to be dis-charged somewhere.

In a cold manifold system the warm water that flows through the thermostat, as well as this excess bypass water are joined together in the thermostat before exiting and being introduced into the bottom of the exhaust manifold. The fact that your are mixing together a lesser amount of 160 degree F engine water (8 GPM) with 10+ GPM of cold lake water allows the aggregate coolant temperature in the manifold to fall below the 110 degree F threshold needed to prevent the accumulation of condensation in the exhaust system.

 

[clinche]

Re: Alarm driving me crazy...

OK ...great you have a ir thermometer ....handy tool in this situation ..... however 180 is too high for any riser temp ..... you should be able to put your hand on the riser at any rpm and not get burned. You may have, like so many engine issues, a couple of things going on here. The differential in riser temp indicates a reduced flow on one side but the fact that both are over heating is curious taking into account the ir reading at the thermo ...Were all the temp readings taken at the same time ? .... if so then both risers are suspect .....just to confirm ...you have done the impellor right ? ...did you check that there is no debris on the raw water side of the ps cooler or oil cooler if you have one ? ...... think you mentioned you did the thermostat ... even new thermos can be faulty but you can easily check with your ir therm.

Did you check that the raw water pump drive belt is tight and is not slipping.

Check for blockage in the leg raw water inlet.

you mentioned that the risers were done fairly recently ..... with all the above in mind I am beginning to suspect that you have the wrong riser gaskets installed ...or incorrectly installed .... easy to check but before you do ...if you can backwash the manifolds with hose ...if you can and see if any crud comes out ..... keep posting and someone will hit the nail on the head

Thanks again for your input. I did change the thermostat, impeller (housing not sure), risers and manifolds. All readings were taken at the same time. At thermostat 140-150, left riser 200, right riser 180. These readings were taken at 4000rpm.

Correct me if im wrong. Temp alarm should not go of at these readings right? So its either a faulty temp sender or its grounding or the same issues with the gear oil sensor or oil pressue sensor.

I have not as yet checked the oil cooler for any debris. I'll include that in my check list. The belts are all firm so that should not be an issue. Could their be a malfunction in the engine circulating pump??

 

[intrepidvoyager]

Re: Alarm driving me crazy...

ok ....lets deal with the sensor issue first ....you are right ...no way the temp sender should be firing the alarm at a thermo housing temp of less than its rated closing temp ... so look on the bolt head shaped ring on the sender ( where the socket goes on ) clean it off and you should see the closing temp ......like 185 with a degree o after the 185 stamped in the surface.....if you have say a 160 sender for example you have found the problem ..... our big block runs at 167 at the termo and we have a 195 degree sender ...BUT I can hold my hand on the riser at any RPM's

ok ...lets assume you got the right sender ...then something else is going on ...... first make sure you have good positive to the inst panel (ip) and also a good ground ... check for corrosion on terminals ........ unfasten the wire to the oil pressure sender and temp sender then turn the ignition to run ...you should not hear any alarm even after the delay .......while you do this see what happens to the temp guage ..... does it move at all ? OK ..now ground the temp alarm sender wire ...should fire the alarm ...if not watch the ip volt meter ..if it swings to high temp you have the temp guage and alarm wires mixed up or there is fault in the wiring ...also the fact that your oil pressure is abnormally high is strange ..normal operating range for a 350 is 35-60 psi ... what could cause this abnormally high reading and also account for the alarm going of is resistance in your wiring ..... your op sender works on a certain resistance range so if you add thru faulty wiring a few 100 more ohms to the sender circuit your guage will read higher ..... that's how to adjust a guage that reads off .... just add the right resistor in line for up or to ground for down. so maybe you have got some resistance going on in the harness .check first off that you have 12 volts at the oil pressure guage ...then detach the sender wire from both the guage and the sender and run a separate wire from the sender to the guage ..start the engine and see if the pressure reading is the same ....if not you got a wiring issue.


now on to the riser issue ...as per the article re raw water cooling its obvious there is something really wonky with your system .... the fact that your temp at the thermo is fine ...even low.... indicates there is nothing wrong with the engine water pump ..if the engine water pump was faulty your engine would overheat in minutes.... also if you were not getting raw water flow thru the entire system and out the leg the engine would heat up considerably ...... ????? ........ i got to tell you that i am interested in your problem as i have been messing around with boats for decades and do not recall ever seeing a radical temp differential sit like this before ???? ..... the only conclusion that i can come up with right now is that raw cooling water is somehow flowing out the exhaust but not thru the riser water jackets ...so thats back to the gasket issue. there is something else you can check ...... in the Y tube going to the leg there are oval shaped flappers that restrict water from back washing up the Y tube and into the riser/manifold on mercs......maybe you got them......... it might be that these are not opening properly so at higher RPMs you are not getting the flow needed to keep the risers at a proper temp ......also guess you are aware but with IR thermos ....if you take a reading of temp in a hose for example and point the ir at the hose clamp ... a refelective surface .....you will get a false reading .....

keep posting ...we'll get to the bottom of this eventually ..GRRRRRRR

couple of questions .....what oil ..viscosity are you using ?? ....also have a look at your dipstick ...is it the original mercruiser dip stick ? also is the tube the dipstick goes in tight or not

 

[intrepidvoyager]

Re: Alarm driving me crazy...

OOPS FORGOT ......check the back of your risers and make sure you do not have VP style risers that do have temp senders ????

 

[Knightgang]

Re: Alarm driving me crazy...

I agree with intrepidv. that you have something out of whack... With the volume of raw colling water bypassing the system and dumping directly into the risers to keep thier temps down, you should not get riser temps as high as you have posted. Either water is being trapped in the risers or the Y pipe to the leg and heating up or there is not enough bypass water flow. This could have happened by using an improper gasket at the thermostat housing... or some other blockage in this area...

Good luck and let us know...

 

[intrepidvoyager]

Re: Alarm driving me crazy...

really good point Knightgang re the thermostat.....also maybe should check that your hoses to the manifold and risers are not inverted ....

http://ocranch.us/tmp/v8cooling.jpg shows the correct layout .

I'd pop over to have a look, but sorry I'm stuck on an island in the middle of the pacific with a bunch of hula girls ...75 degrees today ...hope you guys arnt freezing to death

 

[Knightgang]

Re: Alarm driving me crazy...

72 here today... quite cool at night, but the days are NICE... However, I do not have hula girls here.... Well, I guess I can;t have everything...