Looking for some opinions please. Found a beautiful boat for sale with a 2001 500efi. 338 hrs, springs done at 300 hrs. Compression done 165 high, one cylinder was 145 and one 135. Is that range to much? Was told there is probably a problem. What should the numbers be? Thanks for any info

I like them to be within 10% of the highest number. Did you try squirting a little oil in the low cylinder to see if it cam up?

I will test mines in the next couple weeks also, curious to see what my readings will be!!!

No didn't squirt any oil, but checked cold and then again hot.

you can put rings and rod bearings and lap the valves in a tired old engine and get good compression readings across the board. there are guys on here who won't buy a boat with the engine in it. unless the engine comes with paperwork and a warranty, you pretty much gotta consider it little better than a rebuildable core. and an engine is easier to fix than a hull or stringers or interior, etc. if the boat is better than the other choices you have in your price range... I am not saying buy it anyway, but you can usually get the price down a bit more too.

Solid , Solid advice !

When I was looking to buy I wanted a boat that had motors that where unopened for the reason above. My 500efi's had 345 on them and where never opened and to me that was a good thing. The winter after I got it it went in to get top ends and a good go through that way I knew it was done right by the guy I wanted to do it. Now I don't second gess the work that was done or sead to be done. Just my opinion

Befor the the rebuilds my port was 155 to 160 lbs and stb was 140 to 155 leakd own was 5 to 15%

if a cylinder is 10% or more down their is a problem,it is usually caused from poor sealing at valve&seat.this is very common on the hp500 engines.

agreed, valves not seating, may be starting to tulip a bit