85_sc

I bought a 305 tpi today I was told it came from an 88 camaro. There is a cold start injector the block has 5.0 L on it so i know it's a 305 and it has centerbolt heads and a one piece seal crank so that means it is an 86-89. The one think that i couldn't understand was there was a tag on the block that had a serial number and said it was a mercury marine engine. Did mercury marine ever make a tpi 305 inboard? If so does anybody know the specs. I only live about 10 minuits from merc and I have alot of engine parts I picked up from employees for cheap so it wouldn't suprise me that the guy that had the camaro blew the motor and put in a new one that he got from merc. Maybe I should call up merc with the the serial number and they could help me out.

85_sc

Well i found out some infor the engine is a 91 305 I couldn't find any specs on the camshaft or the compression but the one I have came with a 2 barrel carb and made 180 horsepower at the prop. It could also be had with a 4 barrel holly and intake and that was rated at 240 horsepower at the prop. Boats are somewhat like cars since they do have some "drivetrain" loss but i'm sure it is alot lower that a cars since it's spinning less stuff. He also said that they have these engines orderd from gm to there specs and all of them came with bigger valves that an automotive head. So i'm guessing that means it has 1.94 intake and 1.6 exhaust valves.

bigals87z28

#1 thoes valves are way to big for a 305 bore... probably 1.94/1.50 like on the vette heads,

#2 the 305 is a popular engine for marine use from what i see and under stand

#3, thoes heads could be aftermarket, or just modded 305 heads... look for casting numbers or other marks.

#4 The cam shaft and tpi and all that, you could be putting 240-250 out of the 305. you never know.

85_sc

I really hope that this engine is putting out 240-250 I’m going to take the engine apart this winter during Christmas break and check things out. I have two sets of vortec heads from mercury marine they have Manley stainless steel valves (haven't checked the sizes) and comp valve springs titanium retainers and screw in studs all for the low price of 175 dollars for a pair, I have connections . I hope these heads are prepped the same but I’m not sure because the vortecs were prototypes used by the r&d department at merc performance division (15 min from my house) somebody said some pairs were ported by lingenfelter himself but I haven't dropped a valve on them yet to check for any bowl blending.
All the info on the 305 came from the mercuiser performance division customer service rep. It sounds like the heads are gm castings just "worked" to merc specs by gm according to the rep. But whoever put the tpi on the engine also could have put the original tpi heads on it to so I could be out of luck.