Hello everyone, I just purchased a 1990 350DA (later called 370). She has been well taken care of and all maintenance done over the years as I know the 2 original owners at my boat club. All fresh water usage except a few short trips down the Hudson River to NYC harbor and Long Island sound with return to fresh water slip.
Mercruiser MIE Bluewater 7.4L's w/ Hurth V Drives. Engine serial #s 0C756620 and 0C756621. Just over 1700 hours on original engines so about 56 hours a year in the Northeast. Oil consumption is zero to maybe half a quart per season. And I would like to keep this boat for 10 years until I retire at which point I will buy a 40 or larger with diesels
Compression test on both engines this summer showed that all the cylinders all were in the high 150s to low 160's PSI range, with one cylinder at exactly 150 PSI. So the psi drops from factory spec range from 15 to 30 psi and the variance from the low of 150 to high of 165 is no more than 10%. She will still cruise at 20 mph and run 28 to 31 depending on load at 4100 WOT.
Just a few questions; internet research seems to show there were 2 factory spec compression ranges for these motors with the Mark(Gen?) IV being 180 psi and the Gen V being 150.
1st of all, does anyone know if this engine Gen & PsI info is correct? and secondly can someone confirm that I have Mark (Gen) IV engines based on my serial numbers? (So that my cylinders were originally 180 from the factory and the wear levels are above)
And if if I have Mark IVs originally 180 psi, what is the opinion of those more knowledgeable than me on the relative level of wear vs life expectancy on these motors before I may need a rebuild? In other words, is there any chance I could possibly get another 10 seasons (+560 hours = 2260 hours) out of these motors without a rebuild or repower?
