performance marine filter application

[TominKY]

First time post here. I have a boat with a Gen VI based big block Chevy - stroked 454 in a performance marine application. When I built the engine, I did a lot of research, and learned that people were having problems with the stock GM bypass valve in the block (right above the filter adaptor) were frequently going into bypass mode in marine applications, due to the additional backpressure from oil running through the external cooler, filter, etc. When this happens, oil wasn't getting cooled or filtered and bearings were burning up. So I did what most others were doing - I installed a plug in place of the bypass. This means that all of the oil has to go through the filter and cooler (via an oil thermostat). For that reason I have always run a filter with synthetic media. Since this is a marine application and it is possible to get some water in the oil, the concern is that standard organic media could swell and clog from the moisture and restrict oil flow.

For years I have been running a Wix 51258 filter with no issues. However, recently a friend who is a fellow performance boating enthusiast informed me that apparently the level of quality of the Wix filters had declined considerably. He said that some on here were now recommending some of the better Fram filters. In the past, I had read that Fram should be avoided, but apparently they have upped their game. It appears that their Ultra Synthetic like uses all synthetic media. Can anyone tell me if this is a decent filter, or recommend a good alternative that uses synthetic media? This boat gets its oil changed every fall, usually with less than 50 hours on it. Since it's not in a car going 15k miles/year, filtering efficiency takes a back seat to flow. In other words, the oil stays pretty clean in this thing.

Thanks for your replies.

 

[BrendanC]

pull that plug out and order this. 30PSI bypass. as for a filter, a carquest extended performance or premium is what i’d use. super thick can, silicone ADBV and in the extended protection, polymer mesh backing on synthetic media.

 

[ZeeOSix]

It appears that their Ultra Synthetic like uses all synthetic media. Can anyone tell me if this is a decent filter, or recommend a good alternative that uses synthetic media?

The current Fram Ultra does not use full synthetic media anymore ... that change happened well over a year ago. Get the new Carquest Extended Performance as mentioned by BendenC. It's got full synthetic media with a nylon mesh backing. There are a couple of recent threads about that new filter to hit the market.

Thread:

Thread 'New Carquest EP 20k Filter C&P'

Aug 8, 2025

Carquest EP Extended Performance P84356(7317).

100% Synthetic nylon backed media
20k mile rating
High Flow
Made in Vietnam
$16.99
No efficiency rating

Media 2.25”x50.50”=113.625”

• Glenda W.
• Replies: 81
• Forum: Engine Oil Filters

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[ZeeOSix]

I did a lot of research, and learned that people were having problems with the stock GM bypass valve in the block (right above the filter adaptor) were frequently going into bypass mode in marine applications, due to the additional backpressure from oil running through the external cooler, filter, etc.

What's the details on this setup? Is the oil flow running through the externally mounted oil filter and oil cooler that are plumbed in series? If so, this can also make the oil pump hit pressure relief and cut back supplied oil volume (especially if RPM is high before the oil is warmed up) unless the oil pump pressure relief setting has been increased.

 

[TominKY]

I'm running a thermostatic sandwich adaptor, so the oil only flows through the cooler when it gets hot enough to trigger the t-stat (can't remember the exact temp). I usually run about 180- 200 degrees when running at cruise speed. If I lean on it for a while I have seen it get to around 220-230, but it cools right back down. I am running a standard volume oil pump with the heavier bypass spring. I have been running this particular engine/setup for 13 years, and so far so good. Thanks for the reply.

 

[TominKY]

BrendanC, changing the bypass at this point would almost certainly involve pulling the engine, something I'm not really interested in doing at this point in the game. Thanks for the advice.

 

[TominKY]

Where can I find a cross reference to select a CarQuest filters with the same specs as my current WIX filter? Thanks!

 

[BrendanC]

Where can I find a cross reference to select a CarQuest filters with the same specs as my current WIX filter?

would need to go compare them in person. the wix cross references to this or a fram PH25.

 

[ZeeOSix]

I'm running a thermostatic sandwich adaptor, so the oil only flows through the cooler when it gets hot enough to trigger the t-stat (can't remember the exact temp).

That certainly helps keep the the external oil cooler system restriction down when the oil is cold.

I am running a standard volume oil pump with the heavier bypass spring. I have been running this particular engine/setup for 13 years, and so far so good. Thanks for the reply.

The heavier pump relief spring helps to keep the pump out of relief due to the added flow resistance of the remote filter setup. Sounds like it's never caused any lubrication issues, so I'd just get something like the new Carquest EP (like BrendanC suggested) with the nylon mesh backed full synthetic media since it's also 99% @ 25u efficiency. If you order it from AAP online you can usually use a discount code and get them a bit cheaper. You can order on-line on AAP's website, and pick it up at the store for no added charge if you have an AAP close by.

 

[TominKY]

Apparently that is a different filter - the p85522 for the Carquest. It it too long and too skinny. Local Advance Auto didn't have a PF25 to check it against.

 

[ZeeOSix]

Apparently that is a different filter - the p85522 for the Carquest. It it too long and too skinny. Local Advance Auto didn't have a PF25 to check it against.

Figure out what vehicle specifies a Fram PH25 on Fram's website, then go to Advance Auto Parts website and look up the right Carquest filter for that vehicle.

 

[TominKY]

Looks like it should be 85258. Maybe a little dyslexia?

Thanks for the help, guys.

 

[ZeeOSix]

Per Fram's website, the PH25 fits a 1978 Chevy C10, 5.7L V8. Using that on AAP's website brings up the Carquest Premium 85060. They don't show a Carquest EP available.

 

[TominKY]

So the Premium also has the full synthetic media?

 

[TominKY]

AAP website says "synthetic blend" media, which usually means it has cellulose material.

 

[ZeeOSix]

So the Premium also has the full synthetic media?

Only the new Carquest EP is full synthetic with a nylon mesh backing. But don't currently show one that crosses to the Wix 51258 or Fram PH25.

 

[ZeeOSix]

AAP website says "synthetic blend" media, which usually means it has cellulose material.

Still rated for 10K miles and is 99% @ 20u. Probably flows just as good or better than the Wix you've been using.

 

[TominKY]

My main concern is how the media would react to any moisture that could be present. In a marine engine you can end up getting some moisture in the crankcase due to reversion of the exhaust from cam overlap and wet exhaust, as well as condensation due to the cold lake water flowing through the cooling passages. That's the main reason for the oil thermostat - to get the oil temperature up high enough to boil it off. I'm probably being a bit paranoid about the whole thing, but I just thought it would be best to err on the side of caution regarding the filters that I use.