xhere

I have a 00 32 Sunsation with twin bone stock 502mpi 190hrs. on engines. When I purchased the boat 9 months ago it had 120hrs. I had it in the shop to have the engines checked over and a compression check came back with rather bleak findings!

Starboard Eng.
cyl. 1 100psi cyl. 2 105psi
cyl. 3 100psi cyl. 4 100psi
cyl. 5 85psi cyl. 6 95psi
cyl. 7 110psi cyl. 8 110psi

Port Eng.
cyl. 1 120psi cyl. 2 50psi
cyl. 3 115psi cyl. 4 90psi
cyl. 5 100psi cyl. 6 65psi
cyl. 7 115psi cyl. 8 60psi

I had reservations about the findings so when I brought the boat home I had to check for myself. I performed a dry and wet compression test and had the same results. I was hoping their gauge was inacurate, but no such luck! The wet test did not change the results....
The bizzarre thing is the engines appear to run good, no miss, good idle, pulls 5k rpm @ WOT, Both engines use 1 qt. after about 10-12 hrs of use, oil pressure 30psi hot idle. It seems to me that with compression like this it should hardly run.....Any thoughts on most probable cause? Thanks in advance.

Griff

More than likely you have a bad head gasket on the port even# cylinders.

Overall, I'd say all the compression #'s are weak.

Have a leak down test done to determine where you're loosing compression. Most likely, the engines both need valve jobs. All those #'s are low, especially with that low of hours. Have you ever had the ecm's scanned to verify the hours. It will tell you how many hours and at what rpms they have run, if they've been overheated, or banged the rev limiters a lot.

offthefront

iTrader: (1)

pull the heads ....good valve job ...maybe add roller rockers ....new head gaskets ..... zoom zoom .....

however .... Griff is correct ... leakdown first ....

xhere

I appreciate the advise...I will do a leak down before a tear down...And hopefully the problem remains on the top end! Typically when a head gasket blows will it have heating - cooling problems or erratic temp gauge? Temp gauge seems steady around 170.......Thanks again!

offthefront

iTrader: (1)

eratic temps.... can be steam pockets ....maybe due to bad sea pump ..hense not enough cooling ....hense excessive heat .... and a blown head gasket ....might have started the hole process ....m

mcollinstn

be sure to do your comp check on a warm motor (preferably warm after being up to operating temp on the cooling down side of the curve). Make sure you have the throttle plates wide open when you do the compression test.

I'd love to see a re-test. That's low hours for any sort of issue like this.
Unless it spent some time underwater..

Griff

Chances are the head gaskets are bad between the cylinders--the thinnest point and where they get the hottest. They are more than likely leaking from one cylinder into the other.

If the head gasket was bad where there is water circulation, you would know it real fast. You would have lots of steam and water in the oil.

xhere

The cylinder leakage test did determine a valve problem....I pulled the heads on the port motor and the cylinders appear to be in good shape. I pulled a couple of exhaust valves and it appeared that the sealing surface was toward the leading edge of the valve, not centered in the face of the valve. It also appeared that on 2/3rds of the valve was seating properly. I reassembled heads and took them to a reputable performace engine builder to go thru them....I recieved a call from the builder about a week later and was told that the heads had 454 exhaust valves in it!!! On top of that he said one side had Manley 454 exhaust valves with other side having stock 454 exhaust valves. He said the intake was correct and they where 502 heads... Has anyone ever heard of this happening before? The original owner of the boat bought the boat with 10hrs as a demo and requested 502mpi's installed before he would purchase the boat...So I am assuming that some sloppy reman motors was installed or at least heads anyway!!! The builder installed the correct valves and performed and performed a 3 way cut on the valve and seats.. He states that this process seals better than stock. So if I am living right all might be ok! Can anyone give me the proper torque on the cylinder heads and should the head bolts be replaced. Thanks everyone for your help...

offthefront

iTrader: (1)

first rotation 30lbs ...Second rotation 59lbs ...third rotation 89lbs on short bolts and 92lbs on the long ones ...

I am not sure about replacing em .. ARP's to be sure if you do ...but I'm sure someone will have imput ......m

the duke

ARP bolts with ARP lube. 65 lbs. do it in 3 steps
25
45
65

or ARP bolts with 30w oil. 85 lbs 3 steps

35
60
85