Sundance 340 Mercruisers with V Drive Alarm?

cheetah

New Member
Feb 7, 2010
19
Queensland Australia
Boat Info
Sundancer 340
Engines
7.4 Litre Mercruiser V-Drives
Hi,

I have just purchased a 1999 Sundance 340 with twin 7.4 litre MPI Mercruisers and V-Drives. The boat is in amazing condition and I am ecstatic with it in all except one way. The enginrs run beautifully, oil pressure, temp everything; however after about 15 - 20 minutes running the port engine alarms, one beep about every 3 seconds, everything seems perfect, temp, oil pressure everything. Now this alarm only sounds if the engine is running above about 3000 rpm, if I keep it at 2500 or below it will run all day with no alarm.

When the alarm does sound, if you turn the engine off, restart it and keep it at 2500 rpm or less it runs beautifully.

Any thoughts?

I even wondered about an overheat alarm for the gear boxes, but it doesn't seem to make sense that it dissapears when turned off, restarted and kept below 2500 rpm.

Oh, also, when the alarm does sound there is absolutely no perceptable change in performance what so ever.

Any help would be much appreciated.

Regards,

Jon
 

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I would start by repacing your impllers in your water pumps. Or just replace both water pumps. Don't just replace one, do them both.
 
Hey Jon, one of my friends has the exact same problem on a 2000 380 Sundancer. He has replaced a couple of sensors but it's still alarming. Keep me posted as to what you find out, cause we really don't know why it's doing that.

Thanks, Bruce
 
Hi Tom,

Thanks for your response, I have been doing some reading and came across something that seems a little ciunter intuitive: it seems that by using Premium Unleaded fuel, 98 Octane, this can set off the anti-knock sensors....has anyone heard of this?

Regards,

Jon
 
Also, My buddy has 8.1 Horizons in his 380 so it's going to be interesting to find out what is the culprit.
 
I do not believe knock sensors have anything to do with it. Knock sensors are used to control spark advance based on fuel octane, no alarm should be set.
 
Well folks, I might have an answer, it seems that 1 pin of the anti-knock sensor connectors was bent and it looks to have corrected the problem, at least on a 20-30 minute trial. Apparently there is a wierd effect that the short can cause an alarm, even though there is no anti-knock alarm.

Oh well....am heading to Tangalooma Island this weekend, for those of you not in Australia google it, we are lucky to have this pristine Island and many more just 40 minutes from where I berth the boat.

I shall let you know the outcome next week and thanks for all of your advice.

Regards,

Jon
 
Well folks, I might have an answer, it seems that 1 pin of the anti-knock sensor connectors was bent and it looks to have corrected the problem, at least on a 20-30 minute trial. Apparently there is a wierd effect that the short can cause an alarm, even though there is no anti-knock alarm.

Oh well....am heading to Tangalooma Island this weekend, for those of you not in Australia google it, we are lucky to have this pristine Island and many more just 40 minutes from where I berth the boat.

I shall let you know the outcome next week and thanks for all of your advice.

Regards,

Jon


Where are these anti-knock sensor connectors located?
 
Ok, I have some good news, it seems that the bent pin in the connector for the anti-knock sensor; I just spent two days and did over 3.5 hours running and not the slightest hint of an alarm.

Bruce, I need to appologise to you, I was unable to take a photo for you, unfortunately it was very rough on the way back today and when I went to open the hatch to take a photo for you it wouldn't open, I suspect that it is the pin that connects the hydraulic ram to the hatch that has fallen out but I was in a bit of a hurray and din't have time to open the inspection hatch and sort it out, sorry.

However talking to my mechanic it is quite common, although he said he usually sees it with worn wiring that might short out on the block.

I hope this helps your buddy Bruce,

Goodluck.

Regards,

Jon
 
Hey Jon, one of my friends has the exact same problem on a 2000 380 Sundancer. He has replaced a couple of sensors but it's still alarming. Keep me posted as to what you find out, cause we really don't know why it's doing that.

Thanks, Bruce

I trust by your term of exact it is "EXACTLY" identical, time duration etc.
 
Ok, I have some good news, it seems that the bent pin in the connector for the anti-knock sensor; I just spent two days and did over 3.5 hours running and not the slightest hint of an alarm.

Bruce, I need to appologise to you, I was unable to take a photo for you, unfortunately it was very rough on the way back today and when I went to open the hatch to take a photo for you it wouldn't open, I suspect that it is the pin that connects the hydraulic ram to the hatch that has fallen out but I was in a bit of a hurray and din't have time to open the inspection hatch and sort it out, sorry.

However talking to my mechanic it is quite common, although he said he usually sees it with worn wiring that might short out on the block.

I hope this helps your buddy Bruce,

Goodluck.

Regards,

Jon

Jon, is it the main wiring harness? Is it a single wire?
 
Hi Bruce it is, on mine, a single wire which comes out of the main loom, the mercruiser website had a clear diagram on its website for my engines not sure anout your mates.

Regards,

Jon
 
Again, Many thanks. I found it yesterday in a Merc manual.

It's Mardi Gras day here so we'll check it out tomorrow.:thumbsup:
 
I was there 2 years ago for Mardi Gras....had a great time, I am over in New Orleans again March 10-15.

Please let me know if it is the same problem.

Regards,

Jon
 
We're still recovering from Mardi Gras (HICUP:wow:). My buddy just got back today from a Carnival Cruise and I believe we're gonna look at it this weekend.

He said he replaced that sensor already but wasn't sure about the connector. He had someone helping him cause he couldn't squeeze into that small spot to reach it. I'm probably gonna be the one going in the hole this time.

I'll keep you posted as to what I find.
 

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