head gasket or other issue??

[Oldpos]

i just bought a 2001 PartiKraft 240 with a I/O 3.0L Mercruiser with 435 hours on it. The previous owner said the head gasket kept blowing on him. he said first time they changed the gasket for having two cyl no compression and it blew again within thirty minutes, second time he rebuilt the head and found the dowl pinsfor head alignment damaged and replaced those, again blew within an hour. third time replaced head gasket and bolts, this time motor ran for 4 hours then blew, now has three cyclinders no compression. do you think the thrid time it blew the rings in the lower end? what other possibilities for it to go through so many head gaskets? i am trying to decide weather its worth working on or go buy a used engine. the pontoon boat is well worth the time and effort. i can get a used 3.0l from the 70's with all compression's in the mid 120's and on an engine test stand that i can witness running, or dive into a motor with a history of blowing head gaskets. should i buy a "new" head, head bolts and gasket and try it?

 

[Scott06]

Worth looking at yes would check block and head surfaces are flat and Not damaged

also would check the timing I recall seeing a service bulletin about blowing head gaskets on 3.0s where MerCruiser wanted to set the ignition timing to 1° after TDC. I think detonation May have been a cause of head gasket failure in these engines

 

[Scott Danforth]

the head is most likely warped, and the ignition is most likely way out of time.

What RPM are you running? the 3.0 is 4600 RPM max

so take the head to a machine shop and have it fly cut

the 3.0 from the 70's is too old and 120 psi is a rebuilder. Dont waste your time.

good compression is 150psi per cylinder

if you go to replace the motor, you need to be looking for a 3.0 base motor post 1991 (with the 1-piece RMS crank) for your boat. take a look, they are available nearly everywhere in free boats.

 

[Oldpos]

I have never started or ran the engine, when i bought the boat the owner told me the story of the head gaskets and figured it wasn't worth damaging the motor further trying to start it without looking inside the motor.

with 435 hours i cannot imagine it blew the rings out of it with a rebuilt head, or are these marine motors more sensitive to supposed rebuild heads?

 

[Rick Stephens]

Both Scott's pointed you the right way. In addition to checking/fly cutting the head, you may need to have the block checked and decked if not flat. A GM motor is a GM motor.... none of them are more susceptible to blowing a head gasket than any other. Just need to find the reason for the gaskets popping and fix it. Start with a quality machine shop, take them the block and heads and let the chips fall where it takes you.

 

[Scott Danforth]

• running a 3.0 at 4800 RPM for a half hour on end will blow the head gasket out. the head warps just enough to cause problems
• detonation will kill a head gasket or pistons, which ever is the weakest at that moment (its a coin toss)
• sever detonation will kill the pistons (there will be holes in them)
• improper installation of head gaskets and improperly checking flatness and improperly cleaning the surface will result in multiple head gasket failures
• big block 2-bolt main kits from ARP makes a good head bolt set for the 3.0

 

[alldodge]

Blowing gasket that quick and that many times would tell me the PO has no idea of what hes doing. Would not be surprised that the head was removed/replaced without any checks of head or block

Remove the head and use a straight edge (framing square, aluminum level, other) and feeler gauges to measure any gap found on block and head.

 

[Scott06]

Blowing gasket that quick and that many times would tell me the PO has no idea of what hes doing. Would not be surprised that the head was removed/replaced without any checks of head or block

My money is on this reason, probably coupled with a over heat In It’s past that warped the head.

In in the end I think your better determining what’s wrong vs getting a engine with low compression. The 3.0 I had for many years (20) had 145 psi when I sold it and it was not babied lots of tubing and skiing

 

[Scott Danforth]

My money is on this reason, probably coupled with a over heat In It’s past that warped the head.

In in the end I think your better determining what’s wrong vs getting a engine with low compression. The 3.0 I had for many years (20) had 145 psi when I sold it and it was not babied lots of tubing and skiing

Agreed..... Dad lost a head gasket on the Avanti when he first owned it. the marina did a marginal job on the head gasket and it went about 6 hours later. they did not clean the surface adequately and did not check the flatness.

I then pulled the head, had it skimmed .005 and spend an hour with 3M gasket removing discs to get the block perfectly clean. I also installed ARP bolts..... the motor held for 8 years prior to dad selling it to me, and with me beating on it like I rented it for years..... go back to basics and determine the cause.

 

[Oldpos]

thanks all, i am pulling the head in the morning and taking it to a machine shop. the block i hope is good i will try and check it with a straight edge. I have a funny feeling the PO or his mechanic may not have done the best work, i could be wrong though. The timing i will definetly check too.

 

[Lou C]

When I replaced the heads on my ‘88 4.3 the biggest part of the job was cleaning the block deck and the cyl head bolt holes. Literally took me hrs to get it the way I wanted. Then checked flatness with a straight edge and feeler gauges. Even though it had a previous overheat it was still within specs. The reman heads checked out perfect. I replaced the head bolts with ARP bolts.
before installing the head thread the bolts in by hand to make sure they will thread in all the way. If any doubt use a thread chaser on the threads. Follow torque specs carefully.