Mercruiser 470 3.7 L Blow By issue Piston Removal In boat possible?

[DBEE]

We were sold a cl boat last summer and found out it has a severe blow by issue, did compression and #3 was 40lbs so pulled the head and found blown head gasket but now after pouring a quart of ATF on all 4 cylinders and seeing if we lost any oil in last 24 hrs we lost all the oil in # 3 draining past rings. So the question is can this oil pan be pulled in boat? Seems like plenty of room under and wondering if anyone has done this in a Glasply 18 ft ski boat? I can try it but rather hear back from other experienced marine mechanics if this is doable. FYI no signs of damage to cylinder walls so ring must be broken or stuck in. Be great to pull this piston and fix it. Boat runs awesome otherwise.

 

[Bt Doctur]

Will be a lot easier to just pull the drive, then the motor

 

[DBEE]

I have 8 inches of clearance i just need to lower it to get to the connecting rod and pull this piston. Seems like an experienced boat mechanic would have do this to access oil pump or oil leaks and may know this answer. To pull everything is huge task and the boat is old so not feeling the overhaul time.

 

[Rick Stephens]

I have pulled and reinstalled a running motor in an hour and twenty minutes (for a pinched Y pipe o-ring). It is a lot easier to work on a motor out and it is dirt simple to pull a boat motor. Tons easier than any car or truck.

 

[Scott Danforth]

faster to pull the motor in an hour than it is to try to wrestle the pan out in 3. not to mention your test of pouring in ATF and waiting a week is wrong.

the 470 motor eats head gaskets for snacks as it is a cruddy design. any overheat (as little as 5degrees) will cause the aluminum block to heat enough that the floating bores shift and blow out a head gasket.

check the deck and head for flatness, fly-cut the head as required, install a factory head gasket, then do a compression test.

after you get the motor running, find out why you overheated in the first place and fix that or you will be pulling the head again for another head gasket.

 

[achris]

Don't even think about dropping a sump pan in the boat... Pull the drive (5 minutes), pull the engine, couple of hours tops. There are screws under the engine you can't see, can't get tools on with the engine in the boat.... Not worth the pain to try, just to find out you need to pull the engine anyway.

Chris.....

 

[DBEE]

The boat had tons of power and no overheating at all, was running like a champ but the blow by was so bad i rigged an old paint thinner can to catch the oil. I hear ya on the motor pull but wow so much more to pull, remove and deal with if i can get to the connecting rod and and check a single piston. I owned a european auto repair shop for 30 years. Im confident with difficult was hoping people had an answer if this was possible v engine removal. That turns into a complete go through on every level, gaskets and parts which multiplies the cost and weeks of time. Yes engines, heads, outdrives can be pulled fast but the reassembly is 8X on all parts. Maybe someone will chime in on if this is doable v not. Either the rings are broken or they are carbon frozen but no damage to cylinder walls at all. hmmm

 

[achris]

IT'S NOT DOABLE.

I had oil pan/timing cover problems at about 3 years old on my current engine. Over a period of about 8 months, I had the engine out and back in 11 times. If I could have done it in the boat, I would have. Refitting the engine doesn't involve much more time than pulling it. Takes as long to tighten a bolt as it does loosening it. And there are no gaskets involved in the engine side. The drive is quick, both ways... Watch my videos. And once you have the drive off, you can check things like uni joints, gimbal bearing and engine alignment, things that are annual service items anyway.... 1 gasket.

Chris.........

 

[DBEE]

SInce the head is off and my schedule is full what tried and true chemicals work to unstick frozen rings, I am assuming the rings on cyl 3 are frozen due to blown head gasket and moisture intrusion prob rusted. I have been pouring seafoam in and letting is soak. Seems like this cylinder might have a second life if the rings would free up. I wont have time this summer to take this boat all the way down so alternative fixes would be preferable. My experience tells me these are not broken rings otherwise the piston would have detonated long ago. I can reinstall head and do a running solvent as well.

 

[dubs283]

Seems like an experienced boat mechanic would have do this to access oil pump or oil leaks and may know this answer.

these are experienced boat mechanics giving you the answer, look at their number of posts and ask any member here if they trust these folks advice

nobody is trying to lead you astray, you asked for advice and you got it. in my opinion every member on this thread has giving the best and ONLY advice you should be accepting

do yourself a favor and pull the engine to do the work you are describing, it is the fastest, easiest way

 

[DBEE]

thank you for all the great replies. this 1980 boat however is not worth a total over haul of time and investment. That is why I am on this forum to seek ideas, alternative solutions and to hear from experienced folks who own or repair this 3.7 l motor so I can try last resort options. Thanks for the advice and responses. My apologies if I some how was not abiding by rules or guidelines. We can close this question or delete it off if you like. thanks

 

[achris]

DBEE When you pull the engine out, it's not a total overhaul, it's just pulling the engine out...

I'm sorry we couldn't offer you the advice you wanted to hear. You came here asking if it was possible to pull a piston without removing the engine. Many people, myself included, have offered you our honest, EXPERIENCED opinions. Many of us do this for a living. Trust me, if it was easier, that is the way we'd do it. It's not, so we don't. The faster, easiest and cheapest way is to do what you don't want to hear us tell you.... Pull the engine.... Pulling the engine is a 2 hour job, refitting it is about the same. Any time in the interim would be less than you would spend trying to get things out, and back in, that you can not see. You will spend more time fiddling around with the engine in the boat than it take to R&R the engine. And after 4 hours of not succeeding, you will decide that you need to pull the engine. BTW, cost of parts and gasket to R&R the engine? $0.... Yes, $0.....

What's involved?
Remove the drive (10 minutes)
Disconnect the fuel line and main electrical harness plug (5 minutes)
Disconnect main power feed at the starter motor (6 minutes because sometimes they are a bit deeper into the bilge)
Disconnect throttle and shift cables (5 minutes)
Loosen rubber exhaust boot at the bottom of the exhaust elbow (2 hose clamps. 3 minutes)
Remove 2 rear engine mount screws (sometimes hard to access, so 5 minutes)
Remove 2 front mount lag bolts (any more than 2 minutes and you're 'slacking;')
Hook up a 2 leg chain lifting sling. (lift points are mounted on the engine, 3 minutes)
Lift engine.
Pull the boat out of the way and lower the engine to the floor.

Chris.........
iboats moderator.

I will not close this thread, in hope that you come back and continue to be an active member of this community...

 

[Scott Danforth]

look at the videos in Chris's signature. everything you need to do to pull the drive and the motor.

while chris can get a drive off in 5 minutes, mere mortals take about 20 tops.

realistically removing the drive and the motor is a 45minute job.

back to the 3.7 platypus engine......seriously, the blowby you experienced was due to the bad head gasket. it is a common problem due to the design of the motor.

 

[Bondo]

I have 8 inches of clearance i just need to lower it to get to the connecting rod and pull this piston. Seems like an experienced boat mechanic would have do this to access oil pump or oil leaks and may know this answer. To pull everything is huge task and the boat is old so not feeling the overhaul time.

Ayuh,..... Welcome Aboard,..... Ya need 9" or 10" for the pan to clear the oil pump pick up,......

as stated over, 'n over, Pull the motor, then fix it,......