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Merc cruiser trouble

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jeremy1982

New member
New to this forum and I bring bad news...ughhhh.Well I bought a new to me boat.Its a 96 sea ray 200 signature.Nice boat at a very cheap price!!See where I'm going with this???Anyways it has a 5.0 merc inboard....ran really rough but for the price,even with a motor swap I came out okay.Went to change the oil and got milk!!!pulled the plugs and done a compression test,one side all 4 cylinders were around 120.Other side not so well!80,30,95,100!Im trying to figure out whether its a cracked block or needs a new head gasket???Give me some insight?
 
what sort of job would this be to replace head gaskets?Ive done them on outboards and other small engines but never a v8.The motor doesn't look very complex but I have never tore into it either.Other thing I forgot to mention which is highly important is that the head with the 30 psi had a good bit of water shoot out the spark hole when I first turned the motor .also it lost that 30 psi within seconds.didnt even have to bleed the gauge off.
 
Ayuh,..... The odds are yer problems are much deeper than just head gaskets,.....

I'd pull the motor, 'n mount it to a stand to work on,... Much easier than in the boat,....

I'm guessin' that by the time it's all said, 'n done, yer gonna be replacin' the long block motor,...
 
Well...I got lucky I guess.Tore the motor down today and.....busted head gasket and a cracked head.Block is in good shape though.Just a little hair line crack right beside the intake valve.I have a new question....would a auto head be any different from the marine one???
 
Thank goodness,Ive been searching the internet trying to find a OEM and they no longer make them.There is one one eBay the I may give a shot...just have to rework it
 
I would take both heads in and have them magnafluxed and if good have them both surfaced and ground the same. But thats just me you dont want to go back there any time soon. Do you still see cross hatch marks on the cylinder walls?
 
The cylinder walls look great from what I can tell.Im thinking the rings are in good shape as I took a bottle of Marvel oil and dumped them in all to prevent any rusting while the heads apart,so far its holding and not getting past the rings so I don't think they are fried.I pulled the other head and....what do you know...Cracked in almost the same spot.It was more of a surface crack then a see threw like the other side.I ordered 2 used heads off eBay that have a warranty with them so as soon as they get here I'll have them checked out.Is this a normal fail with these heads?Ive been looking on line and seeing a lot of cracked heads on the Chevy 305/350.I know this is a mass produced head but just wondering
 
Here's a good question,reading the Mercruiser service book and it says on the heads to torque the bolts to 22 ft lbs then 55 degrees on short bolts,65 on mid and 75 on long.However the Chevy 305 book says 65 ft lbs?Why such a drastic difference??Reason I ask is cause when I took it apart they were a lot snugger then 22 ft lbs,well 25 ft lbs with that extra 1/8 of a turn.??Any advice??
 
I always torque them in 3 stages 20, 40, 60 and final torque 65-75 depending on the application
Never liked the degree settings anyway.
Your mis-reading thew torque , its first to 20 Ft.Lbs ,then you mark the bolt and turn it an additional 55 degrees more
 
I think I'm going to go with approach ..20..40..60 then finish with the 65.I would think that would be more consistent then the degrees anyways,Thank you
 
Torque to yield bolts are more for aluminum heads to maintain clamping pressure at different expansion rates and also depends on the type head gasket. If you oil the threads that will increase clamping pressure compared to a dry thread. With a fixed final torque value I will pull it down in at least five steps just for giggles the more the merrier IMO.
 
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