5.7 Compression Test

[Jholly87]

I'm looking a a 220 with 950 hours on it. Had a compression test ran on it and it was not as good as I hoped. The shop did the compression test with out running the boat prior to test. They are going to run the boat and do it again tomorrow. Boat had not been on the lake since late August but owner did run it for 20 minutes on Saturday I think.

180 200 185 185
185 155 150 168

2 4 6 8
1 3 5 7

Good spark
Two plugs do have cracked insulators. No signs of moisture.

[NautiqueJeff]

The ones in the 150's may be a concern.

[bturner]

With the number of hours it certainly would be a concern for me. The next concern is where the lack of compression is coming from. Is it the valves, the rings or a gasket? You may want to have them do a leak down test as well to see if that sheds any light on the issue (https://www.pegasusautoracing.com/do...ocID=TECH00137).

Any way you look at it IMO it's a weak engine and something that will need to be addressed at some point. I would certainly be taking that into consideration during my decision to purchase or at least what I'd be willing to offer.

[Nautiquehunter]

The lac of running could have a lot to do with the weak numbers. I agree with the shop run it and redo the test . 900 hours is not high as long as the engine was maintained.

[Jholly87]

Thanks for the feed back guys! It will be interesting to see if the results are any different after they run the engine. From everything I have read seems like the should have had the engine at least warmed up prior to the test. I guess we will see.

A leak down test would be interesting, not sure I will pay to have the shop do it but I may if the results are the same and I still work out a deal with seller.

[shag]

Cracked insulators? Were they on the cylinders with the lower pressures? If I remember right 150 is the lower end of the spectrum

[Jholly87]

Cracked insulators? Were they on the cylinders with the lower pressures? If I remember right 150 is the lower end of the spectrum

No they were not. Mechanic thought they probably got damaged on original install. The specs that I found for a 5.7 was 150 psi. But regardless 50 psi variance overall is what I am mostly worried about.

[Jholly87]

Well guys I ended working out a deal on it! Hopefully it all works out, I feel like I got a really good deal. I think I will probably run it atleast a year before I rebuild it.