Engine Compression and Leak down test
 

I'm purchasing a used 2008 Sunsation Dominator. The sale is contingent on engine hours scan, engine leak down test and engine compression test twin 496 HO's. So, what documentation should I be requesting for the tests completed?
Photos of actual numbers etc.. Any particular questions to ask. Any help greatly appreciated.
Thanks

if its twin engines I doubt every cylinder will get done per those tests. But you will be told it was. In the auto world they do not even do that form testing anymore. Everything today is looked at with waveform / scope testing among other forms of testing.

I would only use a mechanic that you choose to do the test and not one that the seller chooses.

Thank you

The owner is allowing me to choose. But it's over 500 miles away so I'm not familiar with any shops and have reservations on what to ask for as per documenting.
Thank you

I had a highly recommended mechanic run a compression test on a boat I bought. I found out a year later he lied. I ended up having to do a complete rebuild because the engine sat so long that the cylinders rusted so bad the rings didn't touch a good part of the cylinder. Good thing I bought it cheap. If you have someone do it for you at the location, check it when you get it home, to verify.

if I was in your shoes I would be there and look at every spark plug that was removed also I would verify every reading but keep in mind that you could have great compression say like 160 pounds in every cylinder and and at the same time have high cylinder leakage on a leak down test so if you have 160 compression in the bore and your cylinder leakage is over Say 22 percent that motor could be tired
also make sure you water test it and make damn well sure both engines run in manufacturing specifications at wide open throttle
also there are several weak links on those engines such as manifolds and cool fuel 3 units
my recommendation is to have someone that knows what they are doing give you a mechanical survey on the power plants
also check the transoms for play in the steering pins also upper seal leaking into the bilge and lastly bravoitis and mercathode efficiency
don’t forget to also have the drives surveyed for contaminated gear oil and bent prop shafts also check the carriers for corrosion your spending a lot of money and it’s your investment so protect yourself

activator, thank you for the information greatly appreciated!

I have went and test driven the boat and it ran well at WOT hit the Max RPM and 82 mph. It is very evident the boat has been well maintained by the condition of this 2008 boat. But I agree need to have the powerplant surveyed. Thanks again for all the input!

Most will lie about doing all 16 cyc. especially in boat that is not even 102 inch beam with big blocks. And 496 s at that., Even worse yet for room / access to anything.. When I do all of that for testing, I tell the owner and BUYER it will need new risrer gaskets and manifold gaskets min plus the R& R labor as well. Someone has to pay for all that work because 95 percent of the time you are not getting leak down tools and a compression gauge in the inner engine sides. So with that said the exhaust has to come off and that raises the price of the pre purchase inspection. So with that said if your inspection report does not have charges and or states for any of that - GUESS what more times than not all 16 cyc did not get tested. trust me on that one..

here is an example of exactly what Im talking about. Scroll thru the engines pics and check out the access. No way a guy on a 2 to 6 hour inspection is getting all 16 cyc leaked down and compression tested/ NO WAY. And to do all that for under a grand in cost. Not going to happen with zero access.

Make sure everyone looks at the engine pics very closely. Keep in mind the exhaust manifolds even take up more room side by side than the risers in the pics.The exhaust manifolds are wider than the risers is my point making ZERO access. I know cause I work on 2 to 4 -- 496 s per week during the whole boating season


https://www.boattrader.com/boat/2011...2-ssr-6884653/

Very good information. I will be asking these questions to the shop performing the inspection. I really appreciate the input.
thank you..

If you posted some info about the location, then you may get some recommendations.

How many hours on the engines?? and get the increments of how many hours at each rpm range.

The meters say like 522 and 520. Haven’t seen a engine hour scan read out.

the shop is David Wade Marine.
Baton Rouge Louisiana.

Very good point, I know a mechanic that will do all of that but most are shocked when the quote comes in at 2-3K min depending on travel. If its travel he charges for room/ expenses. Gets expensive fast but so does a motor rebuild.

jeez, how do you even change spark plugs on that?

Salt is more an issue than the block.