Scary Noise when put into gear

B

bryan25rs

Member
Jun 30, 2011
154
Cape Cod
Boat Info
2008 Sundancer 310
Engines
Mercruiser 6.2 Liter V-Drives w/DTS
I did a search and found some similar posts, but none with same transmission setup. I have a 2008 310 DA with 6.2 V-Drives & DTS, 330 hours. I had just come back from a 30 min cruise in 3-4 footers. backing in to the slip i heard a knocking sound coming from the starboard transmision. Before the boat went into the water (314 Hours) I did the following, new spark plugs, new transmission fluid and filter, new seawater pumps, new bottom paint, props balanced, propspeed applied to props and shaft. After i shut down i checked trans fluid, its clean and correct level. The noise is only present in forward and reverse, as the rpm's increase so does the beat of the sound. When in neutral there is no sound at all. i saw some reference to misfiring or ignition related casues, but i have Vessel View and i would get a misfire code, right? Any help or ideas would be greatly appreciated.

Thanks in adavance - Bryan
 
I went and looked at the boat again and noticed that the engine seems to be running a little rough. my port engine is idling at 690 rpms my port is is bouncing from 630 to 660. It also cranks a lot before firing. I unplugged a spark plug on the engine that is running fine and it stubbles the same way, it also does not trip a trouble code of any kind. I was told by a Merc tech that they through a misfire code like a automotive ecu. I have a friend that is a diver i am going to have them dive on it and take a look. I am thinking it is the ignition system. I am going to change out all the plugs, cap & rotor, and wires. Any other ideas, please let me know.
 
It sounds like you should definitely look into the starboard engine, but usually when a stumbling engine is responsible for transmission noise, it's present at idle, but goes away at higher rpms.
 
I was at the boat last night after work and replaced the cap and rotor, it made a difference but engine is still stumbling. There was some corrision on the contacts inside the cap, it might be the origonal one. I also picked up another set of plugs and a wire set and i am going to do those tonight. I have a diver freind coming to inspect the prop, shaft, and cutlass bearing tonight. Anything specific i should have him look for. I also ran the engine up to a higher RPM and the noise does go away, so i think i am on the right track.
 
It could be as simple as your shaft zinc cane loose and is hitting the hull and prop ... as me how I know!!! I thought I had tranny backlash, boy was I happy when I pulled the boat to find the zinc sliding on the shaft
 
I just cant catch a break! the divers found everything to be perfect. I went to go and change out the plugs and wires and saw oil in my bilge. I checked the oil level and it looks like milk. I just changed the oil last weekend. Coolant is clean and the level has not gone down. As far as i know on a Horizon sealed cooling engine the only thing that has sea water going through it is the riser, am i right? Does this mean i need to replace the risers? How often should they be done? It is a 2008 with only 330 hours on it. I pulled a spark plug from each side and the ones on the side i suspect it wet and rusty, is my engine smoked? I have water in my oil and cylinder? I am freaking out!!! Any insight is welcomed and if anyone knows of a good boat mechanic on Cape Cod i would love their contact info.

Thanks in advance, Bryan
 
according to the merc manual, my risers are cooled by coolant the only thing with salt water in it is the elbow, i think? I believe i have a dry joint, warm riser. Anyone know if this is right?
 
check your engine oil coolers(if equipped) they have raw water going thru them
.
post some pics of the engine
 
Check the thread immediately below this, "7.4, water in oil......" Good info in that thread that will help you. First priority is to get that water out of the engine stat.
 
The only cooler I see in the flow chart is for the transmission
 
Can I us a cheaper oil for the flush, and should I change out the filter each time
 
How do I know if it's salt water or antifreeze in oil, I was assuming it was salt water because my antifreeze is clean and the level does not appear to be low. However I don't think I would take much antifreeze to muddy up the oil.
 
Bryan, I have same motors, I would crack risers and have a look; if they have never been done it's time. Will the motor turn over? If not, pull a plug and turn over; water should come flying out. Get water out of cylinders ASAP change risers and multiple oil changes until oil is clean. You most likely had a water jacket give way in riser and it is/was dripping into your exhaust. This is the most common way for a Seawater to enter the motor. You have to coolers on your motor, transmission and Fuel, in that order, after seawater goes through fuel coolor it heads up to heat exchanger and then out to risers/exhaust.
 
Also, download Manual # 37, this will give you everything you need to know about cooling and exhaust on those motors. The best price on dry joint risers with gaskets was at mercexhaust.com.
 
You should not have an elbow on a V-drive setup; you should have just a riser, more than likely a 14 degree that sits directly on top of manifold. The gasket should be closed on each side, that Gasket is more than likely the culprit and/or the riser is leaking badly. With the dry joint setup, it is hard for the riser to leak into exhaust; that's the beauty of the setup, however, that gasket is the only thing that blocks seawater from entering exhaust. Don't worry about the coolers, if either failed it would leak or overheat in case of blockage, either would have anything to do with seawater in your motor. Pray that it's this, as coolant in your oil means bigger problems ( head gasket, crack in block etc) . I would crack risers off stat and inspect.
 
Vessel view will not give you a miss fire code your engine PCM will keep adjusting engine to try to get smooth so you could have a miss fire issue. Vessel view gives you more serious engine damaging codes like low water psi high temp transmission and engine low oil pressure things that will cause serious damage. When a mechanic hooks up his scan tool he will see the misfire on his scan tool.
 
image-2.jpg
Here is my flow diagram

image-3.jpg

This is what my oil looks like

image-9.jpg

This is what the plugs look like, both taken from under riser, the one on the right is from the side i suspect.

image-6.jpg

This is what my riser/elbow setup looks like

image-8.jpgimage-7.jpg

This is the riser i suspect, top view, its next to fuel tank
 
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