188 Sundeck Mercruiser 250 IO Six Warning Beeps

FrankHD

Good evening fellow boaters!

I have the subject boat and engine and I will routinely get six warning beeps while driving the boat.  A look in the owner's manual provides no insight into what the problem might be, other than something is abnormal.  Engine temperature appears to be normal.  Oil level appears to be normal.  It may be my imagination, but the engine seems a little noisier than when it was brand new, but I only have about 30 hours on the engine.  I have only used non-ethanol gas.  A search online has indicated it might be 

1. a water separating fuel filter that needs replacing (I would be surprised if this is the problem as I am only using non-ethanol fuel, and am not sure where this filter is located in the engine compartment),
2. Cooling system water intake clogged (this could reasonably be the problem as the slip I am in has a lot of seaweed in and around it, and a very silty bottom, but I am not sure how to unclog it), or 
3. Low oil level (when I check the oil level with the trim all the way up it looks like the oil level is actually slightly above max... I assume if I trim down it would lower the oil level, which I will check the next time I am anchored out of the swampy slip area).  

On Sunday I got the 6 beep caution alarm as I was motoring through the no-wake zone near the slips and again later when I restarted the engine after anchoring and began to accelerate in deep water.

rholder

I have had similar problems.  Took the boat to an authorized Mercruiser shop and they ran the diagnostics on the engine and got low oil pressure messages.  They decided to change out the oil and they put in Mercruiser's top synthetic oil and then they used Mercruiser's racing filter which from what I understand is larger and allows you to increase the amount of oil in the system.  The boat ran fantastic afterward.  At the end of last season, the shop that I had used was too busy to get my boat in for winterizing.  I took the boat to a local guy who winterizes boats.  I told him about the filter and the oil, and I don't think that he followed my directions.  I'm having the same problems this summer.  I can't get in to another repair shop for at least a month.  I'm going to try and change the oil myself with instructions from the first shop that helped me.  Fingers crossed.  Hope this is helpful. 

FrankHD

So, in the end it turned out to be low gear lube oil.   I discovered this by pouring through the owners manual several times and discovering a page that said that the reservoir is conencted to the alarm system.  Why they didn't say that on the alarm system page, I don't know.  You would think they would list all of the sensors connected to the alarm system in the alarm system section.  Grrr. 

Unfortunately the gear lube reservoir does not come with a dipstick, so the only way to see this was to use a lighted mirror to stick down in the engine compartment between the front of the engine and the bulkhead.  A friend suggested refilling the reservoir and then making my own dipstick.  Stick the dipstick into the reservoir and then mark the dipstick at the full line.  When the level is about 1 inch down from the full line, the gear lube oil level is low.  I ended up using one of those flexible spring-loaded grabbers used to fish things like dropped screws out of tight spaces as a dipstick.  Works well!