Rear main seal leak on 7.4gi?

[jmcr77]

Hi guys. Great forum! I've been reading and learning a lot. My issue is with a 7.4gi in a '98 Wellcraft 260 SE. It just sprung a very heavy oil leak but the engine didn't seize. It sounded to be running normally until turned the key off. Oil pressure around 40psi at idle and about 80psi at 3000rpm, at least if the oil pressure sender and the gauge is to be trusted.

The engine compartment is very tight to try getting a look underneath and see if its a rusted through hole in the oil pan or anything obvious like that. But its pouring oil so it must be something big. To get in there and look under would probably have to take off one side of exhaust manifold and riser.

Based on the symptoms would this seem like a rear main seal leak? Is there any way to fix this without pulling the engine?
If you take the drive out can you get to the rear seal for replacement and maybe install a repair sleeve around the crankshaft?

Has anyone run into a similar issue? Any ideas on what to do in this spot would be very appreciated.

 

[Grub54891]

Does it have a remote oil filter? If so, look for leaking hoses. If not make sure the oil filter is not loose or double gasketed.

 

[Bondo]

The engine compartment is very tight to try getting a look underneath and see if its a rusted through hole in the oil pan or anything obvious like that.
Is there any way to fix this without pulling the engine?

Ayuh,..... Welcome Aboard,....... A digital camera will put yer eyes, where yer head won't fit,......

Regardless what it is,...... the motor's Gotta come out,......

 

[jmcr77]

Does it have a remote oil filter? If so, look for leaking hoses. If not make sure the oil filter is not loose or double gasketed.

It does have the oil filter up high bolted to the port side riser elbow. I traced those hoses down as far as I could see underneath and no obvious leaking there. The filter is clean so should be installed ok, don't think its double gasketed.

With the oil pressure still normal I ran it at idle a bit and watched for any pressurized oil spray but couldn't see anything like that. It just seems to be dumping oil into the bilge from underneath somewhere.

Rear main seal, or hole in the oil pan? Maybe attachment fitting on the dipstick tube? The dipstick was still dry after adding a full gallon of 25w-40 which it then promptly dumped into the bilge. Is that a clue?

Ayuh,..... Welcome Aboard,....... A digital camera will put yer eyes, where yer head won't fit,......

Regardless what it is,...... the motor's Gotta come out,......

Ouch. Thanks for the welcome! I was hoping there was some way to do it with the motor in the boat. With the drive pulled out you cant reach through somehow and get to the rear main seal?

I will try to get a camera under there for a better look. I know for sure if the oil pan needs replacing it wont clear the pickup tube with the limited access down there.

I have heard of JB Weld patch jobs on oil pans but not sure how well that would hold up. I guess use an extractor to pull whats left of the oil, sand it, brake clean, then try to epoxy over it?

 

[GA_Boater]

If you can't see the complete oil pan, how are you going to patch it? By feel? Most likely no matter where the oil is leaking, the motor gotta come out.

Find out where the oil is coming from first before guessing on a fix. From the amount leaking, it shouldn't be too hard to locate the source. Doubt its the rear main if you didn't have oil in the bilge before the gusher. Rears start slow leaking first and ooze. It's probably the pan.

Welcome aboard. We try to give good advise no matter how much it hurts. :smile:

 

[Scott Danforth]

It takes an hour to pull the motor

 

[jimmbo]

Another 'The engine has to come out of the boat' vote. Once out, everywhere can be examined, and the engine can be run, once hooked up for cooling if needed to verify the leak. There a plenty of plugs, seals, senders, gaskets, that can leak. Leaky main seals tend to ensure a well lubricated Starter Bendix, and Motor

 

[Grub54891]

I did have a fairly massive leak on the oil pressure sender on a 62 chive straight 6 years back. Amazing how much oil shoots out of that thing under pressure! But I have to agree with the above posts, pull motor and replace all gaskets and seals as needed. Patching an oil pan won't work for long. The metal is already saturated with oil, a patch don't hold up.

 

[jmcr77]

Thanks guys. Pulling the motor it is, by a landslide.

I'm thinking about building a wood gantry to hang a 1 ton come along chain hoist. I saw a guy used three 6x6x12s dug into the ground about a foot and cemented in. I'm wondering if 10-11 feet is going to be high enough.

For the replacement pan I've read that automotive 454 BBC pans painted with something extra to prevent corrosion like bedliner or thin coat of marine tex should work about as well as the Volvo Penta part, which seems hard to find or expensive.

Does anyone know the right automotive oil pan for a 7.4gi? Dipstick is on the starboard side but I guess it could be relocated to port side easy enough. Its the original motor on a 1998 boat. Will have to get the exact serial next time I'm with it. Guessing its either a BY or a WT, maybe the 1997 LK, would those 3 pans be any different?

 

[Scott Danforth]

Volvo Penta purchased the oil pan from GM. find a GM industrial engine dealer.

as for a gantry, not sure what you have for storage, however my last gantry i built was free-standing in my storage building. the building provided the side-to-side support and kicker braces provided for fore/aft support. I used 3 2x12's across the span and each side had 3 2x6's vertically.

 

[jmcr77]

Thanks. I will check with GM industrial dealers. The current pan has a dipstick tube on the starboard side but the pans I see are for port side. But I guess with a banjo bolt in the drain plug hole, you can turn it and mount a disptick tube on either side of any 454 pan? It seems for boat applications the factory dipstick hole on either side is plugged anyway.

Just checked for serial stickers on the engine but they are all rubbed off from age. Its a 1998 boat with original engine so I think its a "BY" model. Do the previous and next year models of 7.4Gi change much?
Trying to find a pdf manual. I see Don S had a lot of VP manuals among his other knowledge but his 4share links are all expired. Boatinfo has lots of manuals but can't figure out how to save them and something seems wrong with their pictures.

Following advice I got a selfie stick and tried to put the phone under there, mostly got a good look at the sides. It seems the starboard side of the engine is dry but the port side is soaked in oil. The hoses and clamps look ok but possibly the oil cooler area is leaking. From what I could see of the oil pan it looks to be in good shape with no visible rusted areas.

Maybe replacing the oil cooler can be done in the boat. I think will need to pull the motor anyway and deal with some rust below the manifolds. Wish I had a storage building to support a gantry beam but making a wood frame outdoors seems doable. Anyway looks like a project for spring. I'm wondering how to winterize this motor for outdoor storage. Its about to get down to around 25F next weekend.

With a big oil leak, does that still have to be found and sealed somehow? Moisture can get up into the engine through the leaking area? It definitely wont hold an oil change will just leak it all out again.
I've read adding some 2 stroke oil and fuel stabilizer to the fuel/water filter and running the engine for about a minute will work better than spraying a fogger can into the air intake. Is this the way to go?

Any ideas would be appreciated.

 

[Bondo]

I'm wondering how to winterize this motor for outdoor storage. Its about to get down to around 25F next weekend.

Ayuh,...... Pull the drain plugs, 'n drain it dry,......

Air don't freeze,......

 

[jmcr77]

Thanks. Just gravity drain, or try to blow it out with an air compressor? First pour in antifreeze then drain and leave open? Must be a propylene gylcol only formula no ethylene glycol blended in right?

I took a few blind videos with the selfie stick just guessing where to point the phone camera but one of them came out pretty clear. It looks horrible on the port side but think some of the surface rust makes it look worse than it is. Does anything stand out in this mess?
I tried to upload it here: https://streamable.com/7fr20

It seems the back side of the oil pressure sender is badly rusted and maybe blown out. I guess that would cause pressurized oil spraying everywhere which could explain that whole side of the motor being soaked in oil while the other side is dry.

Oil cooler is rusty like most everything down there but it looks to be solid for now, at least more solid than the oil sender.
Power steering fluid was low so there must also be a power steering fluid leak. The steering was stiff last time out.
Power steering cooler looks rough and some hoses are suspect but it doesn't seem obviously leaking, the back of the PS pump itself doesn't look very good. The motor mount also seems angled a bit much, is this another issue?

Any opinions very appreciated.

 

[Scott Danforth]

Just drain. No AF needed

oil sending units do rust

oil cooler is copper, so I doubt it rusted

power steering cooler is copper too

power steering pump is same saginaw pump as GM truck, however the can is slightly different for the industrial/marine motor.

 

[jmcr77]

Ok will just open all the plugs and rod the holes to gravity drain. Maybe remove the raw water pump cover to drain it and probably find it needs an impeller.
It seems 2 stroke oil and fuel stabilizer in the fuel filter should work to fog the engine and the fuel system, just need to shut it off before it starts pulling regular fuel from the tank again, about a minute should be enough? Can I fill with some cheap lighter weight oil just to test for leaks or should keep using the 40 weight?

Oil sending unit does look like the worst part on that side of the motor, its back side looks totally rusted out. The cooler looked rusty but being copper I guess that's just its mounting bracket rusting away.
Whats strange is the oil pressure was always reading normal at the gauge. Went up gradually with rpm then back down at idle no erratic readings or bouncing around, no low pressure alarms or shutoffs.
If it was spraying a ton of oil from the sender wouldn't it show something strange at the gauge? Its on a T fitting with another oil sensor seems to be a separate unit for the low oil pressure alarm, maybe that one rusted through?

Looks pretty high up in the oiling system if the leaking is coming from the sensors on that T fitting. Shows completely dry on the dipstick so that would still indicate a pan leak way down at the bottom right? But a pan leak shouldn't spray oil that high up the port side of the motor. Maybe multiple leaks?

 

[Scott Danforth]

oil sender is on the pressurized side of the system, if there is a rust hole, or other, it will read normal pressure until the oil pump completely emptied the sump.

once the oil is pumped out, nothing will show on the dipstick.

 

[jmcr77]

Thanks. That sounds like it might be whats happening. If the oil is filled and then leaks down below a dipstick reading without running the engine then its probably the pan?

Tried to capture pictures from the video and saw there does seem to be rust and oil traces on the pan by the factory dipstick hole on the starboard side, otherwise that whole side looks dry. The bottom of the pan around the drain plug banjo bolt dipstick tube fitting seems ok.


The port side is completely soaked in oil so that seems to be the leaking area, or at least the biggest leaking area. The rusty sender does seem the most likely cause.


I also noticed some signs of oil weeping by the front main seal.


Would switching from Quicksilver 25w-40 to an oil with a high mileage additive package help swell the seals?
I hear if you switch to high mileage oil you cant go back or you get more leaking than before. Was thinking maybe just a heavier operating weight synthetic like Mobil1 15w-50. Would that be a good or bad idea?

Finally found the info plate on the side of the engine and its a 1997-1998 BY model 7.4GIPBYCCE.
I see Don S uploaded the 1999-2000 EF model manuals which are probably similar to BY and may have good pictures compared to whats on the boatinfo site.
I searched and he referred people to it many times but his 4shared link is now expired (http://www.4shared.com/dir/14518190/c08a758e/EFsharing.html) Did anyone happen to save those files?

 

[Scott Danforth]

if the engine is not running and your loosing oil, it is your pan

looks like rust trail down the side of the pan where the dipstick goes. Pull the motor to get the pan off

front leak looks like the pan to timing cover portion of the oil pan gasket

regarding "additives"........there is no mechanic in a can......

pull the motor, spend the few hours replacing the pan and pan gasket and be back boating.

If it was me, and I had the room, I would go with an aftermarket full sump

https://www.amazon.com/Canton-Racing-18-302-Length-Marine/dp/B002R61RQQ

however summit racing has stock marine oil pans for $150

 

[jmcr77]

Appreciate it. Best plan I can think of is to winterize now then pull the motor in spring for the pan and also try to deal with all that rust. Whats likely the cause of that much rust, leaking exhaust manifold gasket?

Hopefully wire wheel and new high temp paint will handle most of it but probably find some parts that need replacing. The back of the power steering pump looks rough and there's definitely a leak in that circuit somewhere since fluid is low.

This is a gen 6 454 right? Parts are mostly the same with the automotive version if you add extra paint?
It should be 1 piece rear main seal and 1 piece oil pan gasket. Felpro OS34407R will work for a gasket?
The pan looks pretty decent besides that rust trail around the side mounted dipstick tube which isn't needed anyway, think taking it to get that area welded over is worth it?

 

[Scott Danforth]

condensation and crappy paint followed by lack of maintenance leads to rust. once you get it all cleaned up, painted, etc. suggest spraying fluid-film or boeshield on the engine every 6 months

oil pan is thin (as in 28 gauge thin), you most likely need to replace.

could be a gen VI, may still be a gen V. look at block casting.

either way, pan gasket the same

oil pan is industrial engine full-sump on a marine motor