3.7 with a knock - Questions!

[Oshawapilot]

Re: 3.7 with a knock - Questions!

Here is a thread on the subject, but not the one I'm thinking about:
http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/cooling-system-alarm-559511.html


edit: here it is:
http://forums.iboats.com/mercruiser...ressure-alarm-stern-drive-engines-390801.html

Thanks, that would be a mod we could contemplate in the near future, or certainly before next season.

We put another few hours on the engines today, again all seemed perfectly well - oil pressures never went below 40 PSI at idle hot, and maintained better than 60 under power. Found a rebuild plate on the Starboard engine indicating a rebuild had taken place in 1994, as the previous owner had advised us, although it sounded more recent. Standard bearings all around, .030 overbore on the cylinders was indicated. Port engine appears untouched, again as the PO indicated was the case.

Spent a lot of time poking and prodding in the engine bay this evening trying to wrap my head around some plumbing and electrical setups, and then failed again to dig into the portside noise issue any further. Both engines ran like a top all day, however.

 

[Oshawapilot]

Re: 3.7 with a knock - Questions!

Just following up a month later. Have probably put about 10 hours on the engines, some of it puttering about the lake, but a few weeks back we went out for a good long cruise for a few hours running at speed. The engines seem relatively happy at around 3100 RPM and settle into a comfortable temperature zone at that power level.

No signs of overheating on the suspect engine at all and engine oil pressures stayed perfectly comfortable even after an hour at cruise power, both while at cruise, and after reducing power back to idle afterwards. I still haven't narrowed down the sound (It doesn't appear to be the leaky exhaust issue we had hoped for though), but at this point it hasn't got worse and the engine isn't showing any other outward signs of distress, so the plan is to carry on.

She'll be coming out of the water in another month or so for the winter. I've advised that proactively doing the pump impellers and a few other things before next season would be money well spent.