302 compression and riser question

[w1bcr]

hi everyone
the latest project boat a 1974 sea bird mercruiser w/ford 302
model 288204 last owner rebuilt motor and used it one season then
winterized it and it sat for 12 years
got it to turn over after putting mystery oil in all cyls
and got it running seems to run alright but the compression test
showed some low pressure 75 was the lowest 120 the highest
don't mind pulling motor but would prefer to wait till fall or when i
find something i can swap and keep using it
should it be alright ?
and should i replace the exhaust manifolds and risers ?
has closed cooling and held a 20 psi test on manifolds and block
for 24 hours was full of antifreeze when i got it but had been sitting for
12 years
thanks jim

 

[84EdH]

Re: 302 compression and riser question

if its been sitting that many years, the rings and cylinder could have rust scale, so running it might up the compression as the rings reseat. don't push it too hard for 5 hrs or so, then change oil. manifolds/risers.......if they look ok and don't leak, I would just run them.

 

[Walt T]

Re: 302 compression and riser question

Water hasn't been in the manifolds and risers so they SHOULD be okay. I'd replace the riser gaskets just to have a look see. Be prepared for oil leaks. Seals and gaskets don't like to sit and become hard and brittle.

 

[w1bcr]

Re: 302 compression and riser question

Pulling the risers is on my list as I ran it for a bit w/o raw water so gonna check flappers and yes raw water impeller
Also how concernd should I be with pump in outdrive ?

 

[HT32BSX115]

Re: 302 compression and riser question

Pulling the risers is on my list as I ran it for a bit w/o raw water so gonna check flappers and yes raw water impeller
Also how concernd should I be with pump in outdrive ?

Didn't see this thread before I replied in the other one!!

I would replace the pump and housing in the outdrive unless you or someone else replaced it in the last couple of years or so.

Definitely remove the risers and inspect the sealing surfaces. Is that a salt water engine? If those risers are more than about 4 or 5 years old, you might want to change them if they're really rusty.

It appears that you have a Full closed system? If so, your manifolds might be just fine.

Look for evidence of water in the exhaust ports. That will tell you if raw water was leaking past the riser gaskets after shutdown and if so, you will have found the source of possible rust in the cyls if that water sat on top of your pistons over a winter (or if salt, a few weeks!)....It doesn't take very long for salt water to destroy an engine after leaking into an exhaust port with an open valve......


73/Rick