push rods for 305

[udoittwo]

My brother-in-law needed to rebuild his 1997 305 marine motor. The block was cracked so he was told to find another motor that uses the 1 piece crank seal. Did the machine work. When we went to assemble found that the "new" motor is an 1986 and won't accept the 1997 roller lifters. Everything else fits.

We're getting a new marine cam and flat lifters but am wondering about the push rods. Will it use the old push rods or what is the correct length for a non-roller/flat lifters? Are they just standard push rods?

Thanks for your time and any answers and
STAY WELL!
Karl.

 

[Scott Danforth]

correct, roller cams did not hit boats until 1995 for the 1996 model year with vortec heads

push rod length is dependent on rocker style and lifter style. so yes, your existing push rods wont work.

you will be down on power with a flat tappet cam vs the roller cam

if you have vortec heads from the '97 going on the flat tappet motor with stock non-adjustable rockers from the vortec heads, you will need to measure the pushrods

if you have adjustable rockers you can go to NAPA and get pushrods for a 1985 to 1995 truck with an SBC

 

[udoittwo]

Thanks for the info.
HAVE A GREAT DAY!
Karl.

 

[udoittwo]

Now I'm totally confused. JEGs racing has a chart that says Chevy small blocks 265-350 1955-87 use a 7.1 push rod.
1997-07 use a 7.4. Other sources say 7.8 for either style lifter? Most Ebay list 265-350 use 7.8.
There was a complete kit, push rods, flat lifters and rockers, for 1987+back that used 7.8.
IF the early ones called for 7.8. What would the 7.2 do. Just make less power?

 

[udoittwo]

I just looked at Summit racing and they list the 305/350 roller lifters at 7.2?
Does anyone have a stock 1987 or early 305 Mercruiser that is apart that they can measure a push rod for me?
How critical is the .6 difference in a non racing motor?
Thanks for any help,
Karl.

 

[gr8shot]

Half an inch will be the difference between the pushrod not reaching the rocker at all, and performing normally. Since you've got a hodge podge setup, I'd highly suggest measuring to ensure correct length. There's tons of youtube videos showing the right way to measure.