8v71 compression specs

[jusbumn]

I have 8v71 naturals. I have been trying to find compression specs. Appreciation any help.

[MikeP]

DD service manual states compression for an average new V71 engine is 565 PSI and that minimum compression for V71 at 600 RPM is 515 PSI

(spec per Oct, 1989, sec 13.2, page 3 of the manual)

[jusbumn]

Thank You. T reason I ask is that recently I had a compression check done on my 8V71. About 2000 hours. Averaged around 470. Engines don't smoke. Mechanic who did test said it needs to be rebuilt now. What is general opinion? Doesn't burn excessive oil either.

[MikeP]

A classic case of "If it ain't broke, don't fix it." The specs show its compression is low - ASSUMING the compression test was performed correctly. BUT if the engine performs well with no problems, I wouldn't touch it.

[SeaWhisper]

Thank You. T reason I ask is that recently I had a compression check done on my 8V71. About 2000 hours. Averaged around 470. Engines don't smoke. Mechanic who did test said it needs to be rebuilt now. What is general opinion? Doesn't burn excessive oil either.

Run them!

[Boatsb]

Thank You. T reason I ask is that recently I had a compression check done on my 8V71. About 2000 hours. Averaged around 470. Engines don't smoke. Mechanic who did test said it needs to be rebuilt now. What is general opinion? Doesn't burn excessive oil either.

If they run proper RPMs with the correct props. get the boat to it's rated speed, don't smoke and start easily why would he think they need a rebuild? There is something missing in the story. Did the oil samples come back bad? is there a dead cylinder? Is the mechanic looking at a new car?

[Regal2800]

forgive me for going a little off topic, but ff the piston seals were bad the engine would be burning oil and thus smoking. Wouldn't the oil analysis show excess soot in the oil analysis? I guess the previous poster is right to bring up the oil analysis. I just wanted to make sure my train of thought is correct.

[MikeP]

"Is the mechanic looking at a new car?"

Good One!

[Boatsb]

It won't be the first time. I worked at a marina where the owner would put valve grinding compound in the oil to help the engines get closer to repower time faster. I left this job after that and a few other things came to light. Lets just say he was not an honest guy.

[ron6785]

Sounds like the engines are performing just fine. Enjoy !! If you're not smoking and using excessive oil, sounds like you've got a set of bullet proof engines , arguably the best DD's ever made. Do they start easily, which is usually a teltale sign of the compression level.