Is the Mercruiser 7.4 Gen V an interference motor?

[CLi87]

Does anyone know if a Mercruiser 7.4 Gen V is an interference motor? I tried researching it but i'm getting a lot of differing answers, I'm guessing it depends on the generation of the motor but I couldn't find a definite answer to if the Gen V was interference or not.

 

[tpenfield]

It might depend of the application (performance, truck, industrial, marine) and if a high lift cam is used.

Marine applications will tend to use lower lift to get greater valve timing separation. I thought that all of the 454/7.4 generaqtions had the indented pistons, but not necessarily for interference purposes.

 

[Scott Danforth]

if you are spinning the motor fast enough to break a timing chain, yes, the valve would be toast. it is an interference motor

however the likely hood of you breaking a timing chain is about 1 in a million.

there is only .08" of clearance between the valve opening and the piston in a few positions of the crank.

 

[CLi87]

Long story short, I did a compression test when I got the boat and it all tested out fine, did some work to the boat over a couple of months and now the exhaust valve on cylinder #1 is stuck open. I took the valve cover off and the rocker was loose and when I pulled the push rod out I noticed it was slightly bent, was wondering if my valve was also bent from impacting the piston or if it's just stuck from carbon build up or rust or something. All the other valves look fine and move up and down freely.

 

[Scott Danforth]

Pull the manifold and look in the port. Most likely you will find rust

Or you ran lean and tuliped the valve