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1985 Crusader 7.4 Rear Main Seal

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vikingtime

Contributing Member
It's been a long while since I visited the forum (I've been lucky to have a few years with only very minor problems). Currently I have an oil leak in my left hand 1985 Crusader 7.4 serial number 56549. We have some more diagnosis to do but right now it appears to be the rear main seal (tomorrow I'll be running the boat out with a mechanic friend to see if he can find the drip while underway).

Can anyone tell me the part number for that rear main seal? I will be farming this job out to a pro but I'm trying to brace myself for the service cost. I understand that if it's a one piece seal it's considerably less clock time because the engine doesn't have to come out (verses the two piece).

Also, I'm assuming the RMS can be done in the water but I probably shouldn't assume that.

Any information and advice is appreciated.

Thanks
 
i believe this to be a two piece seal. Gen IV correct? 17740 on the Felpro for reverse rotation. $65 last time I bought one. Of course, you are looking at 10x that for labor and a new pan seal, etc.
 
fastjeff said:
Ugh! Is your PCV system working properly? If not, it might be pushing oil past the seal.

Jeff
Click to expand...

Thanks for the info guys.

As for the PVC, my friend (who is a mechanic) seemed to rule them out (I told him I would pick up new ones and he said not to bother-( I think I'll make some calls today and pick them up, seems like it make sense so they can be totally ruled out) but we did pull the air filters off and they are ridiculously clogged - this was caused by the sound proofing (acoustic foam) above desintegrating into a fine black powder. I'd be shocked if this is causing the problem but he wants to start with the basics first. I will be cleaning those today and then we are planning to run the boat later and try to pin point the leak.

This is a significant leak, I'd estimate it's dropping at least a 1/2 quart per hour. After seeing the bilge, I was expecting an oil pan failure but it's in pristine shape and so far all indications are that its coming from the RMS - which definitely seems to be a two piece like Diver Dave said.

Initially I noticed that a good portion of the intake manifold gasket got sucked in (which I replaced 3 years ago). I was thinking that might be the source of the leak so on Sunday I applied Black RTV to it. I guess it's still possible that's the source, it seems unlikely since there was not enough oil there. I haven't run the engine since putting the RTV on.

I'll keep the thread updated as things progress.

Thanks
 
My mechanic friend couldn't make it down tonight to run the boat with me but I found the problem and it's not the rear main seal (thank god!).

He told me yesterday that he ruled out the oil sensor but when I started the engine today I saw a very steady drip coming from what I believe is the oil pressure alarm sender (located close to the dip stick). It took only about 10 seconds to locate it because of the volume of oil that was dripping out. The sensor my friend checked yesterday must have been the oil gauge sender (based on a diagram I just looked at).
oil2.jpg
I will change the sensor out tomorrow (part #97767 I believe) and very likely the problem is solved for $20 verses the unthinkable RMS project.

Thanks again for the help!
 
Your pic is of the low oil pressure SWITCH...they only come in one version...

Those engines do not have PCV valves; just breather tubes going from the rocker cover to the flame arrestor.

Finally, you don't have to give up $20 for a part w a crusader decal - you can get one from a good auto parts store for less than half that...
 
makomark said:
Your pic is of the low oil pressure SWITCH...they only come in one version...

Those engines do not have PCV valves; just breather tubes going from the rocker cover to the flame arrestor.

Finally, you don't have to give up $20 for a part w a crusader decal - you can get one from a good auto parts store for less than half that...
Click to expand...


Mark,

Is this the right part number:

97767Sender, Engine Oil Pressure (Alarm)
http://www.marinepartssource.com/crusaderpb/3507dp59.asp

Thanks!
 
based on your description & the link, I'd say yes..

Your can try a sierra OP22900...Andrew, our host used to carry them. I checked his "store" and is says obsolete.

Standard (SMP) the auto replacement parts maker makes them as well as delco...sorry, no part numbers handy.

They are nothing more than a SPST NC switch that opens once 6psi (nominally) is applied.
 
I changed out the switch and fixed that leak but when testing it I found another and it sure looks like it's the rear main.

Take a look at the video, what do you think?

 
If the front of the flywheel inspection plate is wet then yes, rear main seal is possible...could also be the oil pan seal...

a few paper towel and some brake cleaner should remove the accumulated grime - then an inspection mirror and a flashlight could tell you for sure...
 
Those oil pressure switches break a LOT. Carry a spare. Sometimes they leak, sometimes the internal diaphram splits and the horn always sounds. I've had to replace several at sea... One caused 4 to 5 quarts of oil into the bilge.
 
Quick update:

Visited my local trusted marine mechanic Friday showed him the video and when I told him I had switched to synthetic last season he told me that was the cause of the problem. He suggested I dump the synthetic and refill with straight 40 weight. He also suggested I pull the flywheel cover off and let any excess drain so I have a better picture when I put the new oil in and run it (which I did).

I changed the oil/filter Saturday and ran the boat yesterday. The problem now appears to be "almost" completely resolved. After a 1 hour run I had a very small drop of oil on the new pigmat. I'm going to try this for awhile and see how things go. Worse case he said I can run the boat to him early next spring and he'll change the RMS for $1K total.
 
Terrific advise! Glad to hear it's working out so well.

Jeff

PS: Agreed on the short life of pressure switches. This is the first year I didn't have to replace another one. (Yes; I carry a spare.)
 
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