My Mercruiser I/O Experience

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Ken Butti
Posts: 35
Joined: Sat Oct 30, 2010 6:26 pm
Location: Lacey (Olympia), WA

My Mercruiser I/O Experience

Post by Ken Butti »

Got my Sea Lancer out for the first time on June 2nd (see attached photo), and had it out a total three times last month. The 120-HP Mercruiser engine had a loud "ticking" sound that concerned me, along with the crankcase being over-pressurize (blow-by). Performed a compression check and got 149-149-90-130. Yikes! I was hoping it was the head, but when I pulled it, it looked fine. However, I then saw and felt that the #3 cylinder had deep grooves in it. So much for just a top-end overhaul. I tore down the engine and found the source of the "ticking" and low compression (see attached). I was probably very lucky I didn't have a major engine failure out on the Puget Sound! Connecting rod looks a little twisted, too.

Long story short, I surmised that the P.O. sucked a valve at some point, pulled the head, and either figured the piston & cylinder escaped damage, or intentionally left it (for me!). It's in the shop now, getting a short-block treatment. #3 cylinder will need so much taken off to get the grooves out that they have to bore out other three cylinders, also. Will wind up with slightly larger displacement, four new pistons and rings, all new main & rod bearings, and probably replace #3 connecting rod.

Hope to have my new engine by next week. And, a boat that should give me years of trouble-free fun!
Valve-Damaged #3 Piston.jpg
Valve-Damaged #3 Piston.jpg (98.22 KiB) Viewed 20351 times
Friend's Dock on Long Lake in Lacey, WA.jpg
Friend's Dock on Long Lake in Lacey, WA.jpg (153.64 KiB) Viewed 20351 times
Ken Butti
1969 Peshtigo-Built Sea Lancer
Lacey, WA
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