Engine Alarm At Idle, Then Slowly Fades Out. Possible Idle Overheat

[TwoCamSam]

Sorry for the long post, just trying to give as much detail as possible up front.

2007 4.3L TKS (2008 deck boat)
Serial# 1A041404

Just put the boat in the water about a week and half ago for the start of the season. Picked this boat up last year. 1st boat, so I am reading and learning as rapidly as I can. Please excuse any ignorant questions for a boat newbie. No stranger to turning wrenches though.

Before the boat went in the water, friend of mine came by few days before and we dropped the lower unit and changed the impeller. Old one still looked good, but I had no idea when it was last changed.

Dropped the boat in the water a couple days later. Left the boat on the trailer, but the backed it way down the ramp to get her started and let it idle 15-20 minutes or so. Just wanted to make sure it wasn't overheating, oil pressure good, and checking for water leaks (had just installed a new drain plug too). Everything checked out, unhooked the winch strap and pulled her into our slip.

Ran the boat for a couple of hours that day. Temps and oil pressure looked good. Took the boat out the next day for about 30 or 40 minutes. Had some family on the boat. We stopped in side channel off our lake super low speed to chat for a bit, just enough throttle to keep her going. After a few minutes, I heard the engine alarm go off (at the time I wasn't aware that's what the beep was) It was a solid tone, but after a couple of seconds the tone faded. It started loud and got quieter and quieter and then it stopped. Didn't think much of it at the time. Took the boat back to the slip (1000yds away or so).

Found out the next day that was the engine alarm that went off. According to my manual, solid is for engine temp. Went back down to the slip, started up the boat and let it idle. Took about 15 minutes to come up to 160ish. I keep watching the temp and it slowly kept creeping up. Eventually it got to about 180. I figured maybe since I was just sitting in the same location at the slip and not moving, I could be sucking up warm water from the exhaust. I went to bump the trim up just a tad to see if I would see the gauge move at all. As soon as I bumped the trim up, the engine alarm went off again. Same thing. Started loud, then faded out slowly. Temp was nowhere near 200 on the gauge when the alarm is supposed to go off (I know they could be misleading).

I'm going to pull the boat out of the water today and bring it up to the house to start some troubleshooting. Should I do any additional troubleshooting while it's still in the water vs having it beside the house on muffs?

Just looking for next steps on where I should I start. Boat seems to run dead at 160ish going down the lake.

Other info on the boat:
Raw water cooled (from what I know, still learning. I don't see any additional cooling/water tanks or anything) So it seems it's just pulling water from the lake and back out the exhaust.
Freshwater lake and from what I know it's always been freshwater. I'm the third owner.
Not sure if manifold/risers have been replaced in the past or not, but again all freshwater. While the boat was idling, I could put my hands on the top of each riser. Wouldn't want to keep them there for more than 3 or 4 seconds though. One sides does not seem hotter than the other. No signs of leaks/rust/etc. around them.

 

[Captain Caveman]

I guess my first test would be in the water again, playing with the trim to see if that continues to cause the alarm. If so, it sounds like an electrical problem.

You could also change the motor's trim in different water depths just to ensure that it's not causing the problem.

Other things to check would be to unscrew the intake screens on the lower unit and make sure that they are clear. You could also check the pee hose inside the motor to make sure that there are no obstructions.

You could also check the temp gauge to ensure that it is giving you an accurate reading.

On a side note, my Suzuki gives me a heart-attack once per year when the alarm goes off to tell me it's time to do standard maintenance.

 

[alldodge]

Things that can give a solid tone alarm besides temp are
oil pressure low or outdrive gear lube low

All 3 are switches and turn the alarm on by closing and connecting a Tan/Blue wire to ground

How much lube is in the drive bottle?

 

[TwoCamSam]

I guess my first test would be in the water again, playing with the trim to see if that continues to cause the alarm. If so, it sounds like an electrical problem.

Was thinking the same thing here as well. I'm going to go start it in just a few. Will play with the trim at various times while warming up to see if it goes off.

You could also check the pee hose inside the motor to make sure that there are no obstructions.

Where exactly is this "pee hose." I've read some other posts mentioning this as a check. Not sure which hose it is.

You could also check the temp gauge to ensure that it is giving you an accurate reading.

I have an IR temp gun I was going to shoot the engine with to check this as well. Is the best spot to hit the thermostat housing?

How much lube is in the drive bottle?

Bottle is full. Another newb question about this. When the impeller was change recently, mechanic cracked the drain screw on the lower, obviously filled it up once the job was complete. Is this the same lube as what the drive bottle reads, or the the lower unit sealed with it's own gear lube? Just curious.

 

[alldodge]

Your motor doesn't have a pee hole

Is this the same lube as what the drive bottle reads, or the the lower unit sealed with it's own gear lube?

Yes same bottle. As a test, if the alarm is sounding disconnect one of the wires going to the lube bottle. If alarm goes off, then lube bottle switch is hanging and may need replaced

Can do the same disconnect test for the temp sender and oil pressure switches. (Not the oil pressure switch that supplies power to the fuel pump)

The TB-V module also can sound the alarm

 

[alldodge]

Delete: wrong thread

 

[TwoCamSam]

Your motor doesn't have a pee hole



Yes same bottle. As a test, if the alarm is sounding disconnect one of the wires going to the lube bottle. If alarm goes off, then lube bottle switch is hanging and may need replaced

Can do the same disconnect test for the temp sender and oil pressure switches. (Not the oil pressure switch that supplies power to the fuel pump)

The TB-V module also can sound the alarm

Got it. Going to head down, start the boat, and run a couple of tests while it's warming up. Will post back with findings.

 

[TwoCamSam]

Went and started the boat and let it idle in the slip for about 20-25 minutes.

When I first turned the key to on, the alarm sounded as usual for the test. I decided to wait a bit to see what would happen (suspecting the alarm needs to be replaced as well) after about 5 or 6 seconds of the normal high pitch squeal, it slowly started to fade like it was dying, then quit. Turned the key to off, then back to on and it barely made any noise.

Anyway, started the boat. Took a solid 10-15 minutes it seemed to crack 160-165. After a bit it very slowly started to climb. My 20-25 idle time produced a temp of 190.

The gauge is accurate. I was hitting all over the thermostat housing and base of the intake manifold and it was right at what the gauge was reading. I noticed the sensor (when hitting with IR gun) on the port side of the thermostat housing was reading about 20-30 degrees less than the sensor on the starboard side. Assuming the port side is getting the intake of fresh water before its cycled through the block.

I played with the trim up and down while it was warming up multiple times. No alarm.

The alarm finally tripped at 190 on the gauge. Also probed the motor temp again and it verified 190-192 on top of the thermostat housing. Base at the manifold was slightly lower.

When the alarm tripped, I didn't have time to unplug the drive oil sensor before the tone slowly faded as it has been doing. Shut her down after that.

I was curious and probed the manifolds and risers. I'm hoping I don't need to replace these right now, but it is what it is if so. So, if I probe the riser where the water inlet is, it was about 130-140. Could have kept my hand there for quite awhile. If I probed dead on top of the riser, I'm in the 190-200 range. Both starboard and port manifolds returned approx. the same reading. No drastic difference between the two.

If something was up with the new impellor, I feel like it would have overheated much faster than it did. Is that true?

Oil pressure was running about 60psi when cold. As she warmed up, dropped to about 50-55 psi just idling.

Could this just be a thermostat not opening all the way restricting some flow? I probably should change it anyway. $30 part and I don't know when/if its ever been changed.

Thanks!
-Sam

 

[alldodge]

I doubt its the lube bottle, you proved its the temp switch, and your are getting hot.

One side of the mans will always be hotter then the other, its just water flows easier to one side

Get a short piece of clear hose and fittings at the hardware store. Connect the hose between the thermostat housing and the outdrive. With motor running see if you see air bubbles

 

[TwoCamSam]

Get a short piece of clear hose and fittings at the hardware store. Connect the hose between the thermostat housing and the outdrive. With motor running see if you see air bubbles

Will do! I assume you mean to drop the short piece of clear hose between the current line from the outdrive to the thermostat housing, not try and replace the whole bit just to watch for air. So a piece of hose roughly the same size, barb to put them together, couple of clamps.

If I do see bubbles, that obviously means I'm getting air in the cooling system which isn't good, but what exactly could/would be the culprit causing air to get in from the outdrive?

 

[alldodge]

Yes short piece

Might be the pump housing or hose fitting

 

[TwoCamSam]

Quick update. Haven’t been able to get the clear hose yet from the hardware store.

However, I did go ahead and put in a new 160* thermostat because I had it on hand. Seems like it had never been replaced so it was well over

New thermostat didn’t help. Did get a look at the check ball valves and they are sealing well too.

I’ve pulled the lines from the transom at the power steering cooler inlet (which just seems to be a black pipe. No screens or anything in it) I’ve got plenty of water volume when starting the boat.

Also pulled the line at thermostat seems to be plenty of flow as well.

took the boat out for a ride yesterday. Slow overheat sitting at the dock, but as soon as I give it just a bit of throttle I’m dead on 160 the entire time I’m running down the lake

 

[alldodge]

Lowes and Home depot both have clear hose, its in the plumbing section