Mercruiser 470 Woes

[Bookworm007]

Let me set you the stage, I have a 1976 21ft Bayliner Hardtop cuddy cabin that I got from a family member for "free". I am slowly learning nothing is free when it comes to boats. The hull is in good shape, it has a clean fuel system, new floors, the 470 has a new headgasket, rebuilt head, good exhaust manifold, 4 inch heat exchanger, alternator conversion, recently serviced strendrive, and I have been out really enjoying the boat, but........ Last time I was out the engine seems to have developed a knock whenever above 2 thousand rpm. The engine has 145 psi on all cylinders, electronic ignition and 25 psi of oil pressure warmed up at idle and 45 psi at 3500 rpm. I haven't cut open the oil filter but I did drain a small amount of oil from the pan and could see what might be very fine metallic particles.

Here is my dilemma..... I can get a 470 short block for around 1 thousand dollars, I found another boat that is trash a "rebuilt" 470 for 300 bucks. Also found boats with the parts needed to swap in a 350 or 4.3l engine. (Mounts, exhaust, sterndrive) my Bayliner has stringers wide enough to accommodate a v-engine.

What should I do. Obviously short-term repairing the 470 is the cheapest decision..... But I could part out the 470 and replace it with the 350 or 4.3 and make this boat easier to sell should that day come.

Thoughts advice? Options other than a bad bearing? Ways to diagnose a bad bearing without pulling the engine?

Thank you!

 

[Scott06]

350 or 4.3 swap is best approach, especially if you can find a good condition tear out. You’ll have a modern power plant which will be better regardless if you are going to use it or sell it down the road

 

[QBhoy]

Get rid of the 470 ASAP. Like ground hog day engine after engine, unless you are fanatical about these things and spend more time tinkering, than actually using the boat. Best suited to the retired and stubborn amongst us really.
a 3.0 will drop straight in, but if you have the required and the ability, get a 4.3 in it and likely only need an inch or two in pitch change on the prop.

good luck.

 

[Bondo]

Here is my dilemma..... I can get a

Ayuh,...... Welcome Aboard,....... Buy the rotten hull, with the runnin' 5.7l / alpha drive, 'n swap it's driveline, Complete, in yer keeper boat,.....

 

[QBhoy]

Ayuh,...... Welcome Aboard,....... Buy the rotten hull, with the runnin' 5.7l / alpha drive, 'n swap it's driveline, Complete, in yer keeper boat,.....

A sound idea. Only downside might be getting rid of the old hull ? Not an easy thing to dispose of where I live, at least.