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Mercury 525 Service

Motoxxxloak

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Either I am terrible at the search function (and Google) or there just isn’t much information on this.

I have a 525. Roughly 150hrs. I’d like to replace the water fuel separator (currently have Sierra 18-7844 installed) and the oil filter (Merc 35-866340K01 installed). I feel as if there is at least 1 or two more filters that should be replaced as I thought I saw what looked like a small fuel filter on back/top of the engine?

I had really good experience with Wix filters on my last big power motor and would like to use them again unless there is something better the brain trust recommends?

I also used to run Kendall GT-1 in that motor but am not finding any good suggestions to run in this motor? Boat never leaves havasu and might see 20hrs this season. Any input is greatly appreciated!


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BDMar

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I have the Wix Racing filter for that engine and also all the fuel filters.
 

port austin pirate

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Either I am terrible at the search function (and Google) or there just isn’t much information on this.

I have a 525. Roughly 150hrs. I’d like to replace the water fuel separator (currently have Sierra 18-7844 installed) and the oil filter (Merc 35-866340K01 installed). I feel as if there is at least 1 or two more filters that should be replaced as I thought I saw what looked like a small fuel filter on back/top of the engine?

I had really good experience with Wix filters on my last big power motor and would like to use them again unless there is something better the brain trust recommends?

I also used to run Kendall GT-1 in that motor but am not finding any good suggestions to run in this motor? Boat never leaves havasu and might see 20hrs this season. Any input is greatly appreciated!


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Book says replace oil en filter at 25 hours drive 50 hours or seasonal Merc recommends their 25/40 oil. I have run Merc oil now run 15/50 Amsoil dominater. seems to work well. Me and a lot of others change drive oil at 25 hours, A lot of the guys say Mobil 1 15/50 works well much better price all kinds of opiniuns on oil. the only other fuel filter is on the electric pump under the engine, But at 150 hrs it should be fine. ther is a small air filter at the back in top of the plenum have to look at manuel to get change hrs. Do you have the Merc manuel. can get online if not. I usually just use Merc filters. Others who are more knowledgeable than me will give you some input
 

02HoWaRd26

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Orielly’s was 60$ for 10q of Mobil 1 synthetic and the Wix filter for my 496 two weeks ago.
 

Fun Times

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525...I feel as if there is at least 1 or two more filters that should be replaced as I thought I saw what looked like a small fuel filter on back/top of the engine?
Do you have your engine serial number handy? as this engine does have an additional fuel filter up top / inline with the fuel injector rail but Merc had a few designs of filters so your engine serial number would be needed to help ensure you find the correct one/all your parts.
 

Runs2rch

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Fram Racing Filters are built better than the Wix Racing filters now. They filter better, and have a bypass.

HP4 Fram oil filter

Wix 33226 for water separating fuel filter.
 

hold_j

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Well shit, I Hope u put more then 20 hours this season you channel queen haha im at 12 already since the beginning of February lol

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Duck'ed_Up

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Well shit, I Hope u put more then 20 hours this season you channel queen haha im at 12 already since the beginning of February lol

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Hahahha you said “channel queen” I’m dead


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02HoWaRd26

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Do you have your engine serial number handy? as this engine does have an additional fuel filter up top / inline with the fuel injector rail but Merc had a few designs of filters so your engine serial number would be needed to help ensure you find the correct one/all your parts.
OM958384
Seems i have the spin on, on the starboard front corner and the canister on the port rear corner.

So what about plugs and what is the capacity of the oil do you know?
 

Fun Times

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OM958384
Seems i have the spin on, on the starboard front corner and the canister on the port rear corner.

So what about plugs and what is the capacity of the oil do you know?
OM958384 comes up as an RACE STERNDRIVE 2007 525 EFI HIGH PERFORMANCE 525EFI SGL PLUGIN WPS 525 EFI BRAVO Model Number 4WH2225WH 525.

Here's some parts catalogs for your engine,

Spark Plugs are new Merc part Number 33-8M0114747 (old number 810883) which comes out to be Mercury 810883 replacement spark plugs NGK part box # 7822 = Plug # NGK BPR6ES (NGK V-line-2), https://www.mercruiserparts.com/8m0114747-plug-bpr6es-4

See item number 48 for the plugs, https://www.mercruiserparts.com/bam/subassembly/31347/13369/40

Oil Capacity should either be 7 or 8 quarts of engine oil as it varies as you can see here if desired, https://www.mercruiserparts.com/hi-performance-engine-oil-chart

 
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fastenuff3

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Either I am terrible at the search function (and Google) or there just isn’t much information on this.

I have a 525. Roughly 150hrs. I’d like to replace the water fuel separator (currently have Sierra 18-7844 installed) and the oil filter (Merc 35-866340K01 installed). I feel as if there is at least 1 or two more filters that should be replaced as I thought I saw what looked like a small fuel filter on back/top of the engine?

I had really good experience with Wix filters on my last big power motor and would like to use them again unless there is something better the brain trust recommends?

I also used to run Kendall GT-1 in that motor but am not finding any good suggestions to run in this motor? Boat never leaves havasu and might see 20hrs this season. Any input is greatly appreciated!


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the small filter on back off engine you need to take apart there is a filter inside. i got a cleanable filter from teague. i use valvoline 20w50 vri and wix racing filters are good
 

02HoWaRd26

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the small filter on back off engine you need to take apart there is a filter inside. i got a cleanable filter from teague. i use valvoline 20w50 vri and wix racing filters are good
Any idea what you ordered for the cleanable filter? Also how often do you service that one?
 

Fun Times

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Any idea what you ordered for the cleanable filter?
For others with the 525 EFI's following along here, your design fuel filter at the fuel rail should be depended on what your engine serial number is as the earlier years had a different type/design than the newer 525's... [U]02HoWaRd26[/U] has the second design.

The first design injector fuel filter serial number range listed is 525 EFI - 0M900146 THRU 0M953619 , Fuel Rails And Injectors

The second design falls under the rest below,
525 EFI - 0M953620 THRU 0M956326 ..
525 EFI - 0M956327 THRU 0M962885 ..
525 EFI - 0M962886 & Up ..

First design item # 22,

2235-807174T FILTER, FuelACT$63.42$61.001
Second design # 27,

2735-8M0050994 --FILTER, Fuel848355SS/ACT
$35.97$35.321
 

02HoWaRd26

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yes the factory one is paper
I haven’t gotten back there but the new filter arrived today. Do i need any special tools? Any tips or tricks to this or once back there it’s obvious??
 

fastenuff3

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I haven’t gotten back there but the new filter arrived today. Do i need any special tools? Any tips or tricks to this or once back there it’s obvious??
use line wrenches and pull housing out and then pull housing apart on vice
 

02HoWaRd26

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use line wrenches and pull housing out and then pull housing apart on vice
Is this the same one??? Jesus Christ if so is it reverse threaded? Or is it mines never been opened since new? Cause this mother Fuq’r i cannot get opened.
DCC20329-E79A-469A-B940-282543DB2D7D.jpeg
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02HoWaRd26

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yes that is it and it is not left hand thread. i have copper jaws in my vice so i put it in the vice alot easier to get apart
Yea i got it today, used vise with my an fitting clamp, but took a 3’ breaker bar. WTF lol.
added a tad of grease on the oring, but idk I’d that filter had ever been changed it was pretty gross.
 

evantwheeler

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aeromotive 100 micron p/n 12604. i check it yearly.make sure its the same because i have a 600sci it looks the same
I'm not up to speed with custom boats, but in sand cars, we put a 100 micron BEFORE the pump, and a 10 micron AFTER the pump. Are you sure that a 100 micron goes right there before the fuel rail, and not a 10 micron?
 

02HoWaRd26

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I'm not up to speed with custom boats, but in sand cars, we put a 100 micron BEFORE the pump, and a 10 micron AFTER the pump. Are you sure that a 100 micron goes right there before the fuel rail, and not a 10 micron?
It’s what Teague recommended him as well me when i ordered this one from them.
 

02HoWaRd26

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Any heads up on an impeller, now that I’ve officially taken over @Motoxxxloak ’s thread, since he’s afraid to get dirt under his nails and has a shop do his labor 🤣🤣🤣lol sorry buddy lol.
 

02HoWaRd26

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Other than it’s expensive, any reason not to use the case of Kendall GT1 i have sitting here for the oil change?
 

Fun Times

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Other than it’s expensive, any reason not to use the case of Kendall GT1 i have sitting here for the oil change? (impeller?)
Search online impeller kit part number 46-807151A14 for your preferred pricing options.. Item number 4, https://www.mercruiserparts.com/bam/subassembly/31347/13369/170

What's the engine oil weight of your GT1.

Quicksilver Marine Oil 25W40 or Quicksilver Synthetic Blend Marine Oil 25W40
Or,
Mercury High Performance 4-Stroke Synthetic Blend Oil 25W50 Recommended for use in all Mercury Racing four‑stroke engines including: FormulaRace and Verado outboards and 525 EFI through 1650 sterndrives.

Outside of oil preferences, 'These are some of the recommended weights to use.
 

Shlbyntro

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Merc 25w50
Or Castrol 20w50

I've had great results from both.

Delo 15w40 is also great but can have lower oil psi when returning to idle from hard running
 

Lavey 29

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I would use a racor or a FST spin on filters. I would use a Sierra fuel spin on filter before I would use a Merc fuel spin on filter. Wix fuel filters hugely over rated as they offer nothing great over any other fuel filter and they rust badly when water is in the fuel. Merc rust badly as well. I cut filters open 5 days a week to know the good - the bad and ugly. Just saying
 

02HoWaRd26

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Anyone know what year they took the 525 from a distributor to coil packs?
 

02HoWaRd26

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So Mercury suggests the use of the NGK BPR6ES, well there are two different part numbers for this plug. I emailed NGK and they said
“Hello,
Thank you for your inquiry. The difference in the stock number is that 4008 comes in a traditional box and has a SOLID terminal nut. 6775 comes in a blister pack and the terminal nut can be removed. For a high vibration marine engine, 4008 is preferred so that the terminal nut does not come loose“

So for anyone else using this thread for 525 info the preferred spark plug for the 525 is the .......

NGK BPR6ES 4008
 

02HoWaRd26

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I will update in this thread.
But have spent about an hour researching the “mechanical fuel pump oil change”

I’m going to pull mine out and do the impeller as well on the bench.
I ordered a two pack of the Bravo drain plugs (79953Q2) and a 3/8-16 tap as well a brand new 5/16” drill bit.
Will remove and drain the pump, then there shows to be a flat spot which a lot of people have used as their drain plug location (fumoto valve would be bad ass is all i can say)
Then it should make the job 10 times faster next year. Mercury makes a huge ordeal out of this service but cheaped out on the pump by not putting a drain on it. Hopefully i remember to take a bunch of pics along the way.
 

FROGMAN524

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So Mercury suggests the use of the NGK BPR6ES, well there are two different part numbers for this plug. I emailed NGK and they said
“Hello,
Thank you for your inquiry. The difference in the stock number is that 4008 comes in a traditional box and has a SOLID terminal nut. 6775 comes in a blister pack and the terminal nut can be removed. For a high vibration marine engine, 4008 is preferred so that the terminal nut does not come loose“

So for anyone else using this thread for 525 info the preferred spark plug for the 525 is the .......

NGK BPR6ES 4008
These are what came out of my 600s which are same 502s as 525.

IMG_3766.jpg



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02HoWaRd26

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These are what came out of my 600s which are same 502s as 525.

View attachment 964311


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Yes, however there are two part numbers for the BPR6ES the 4008, as well the 6775. The difference is packaging as well that the 6775 the terminal nut is removable and could loosen in the Marine world. As per NGK.
 

02HoWaRd26

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A8A541B3-EB55-436C-AE6F-D3570407D883.jpeg
7BDD0A2B-7EA7-4D4B-8D56-3BC276145CEE.jpeg

Looking down at what i gotta do! Removed the battery box and prop mount just for ease of space.
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Definitely was time for the impeller.
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Marked drilled with 5/16” drill bit. Drilled real slow and at about a 70* angle so when i got in minimal shavings would hopefully get in. Slight hit with the bevel bit to clean the outer edge. Then i ran my 3/8-16 tap in. Blew out from the fill out the drain into a paper towel was happy to see no shavings come out.
8BC6C9BB-0F44-496B-A61A-3BC008EEB571.jpeg

Test fit all was perfect, except realized that the plugs needed polished.
45D93727-9352-4556-BDAC-C7A2A3B463D1.jpeg

Now when the new impeller gets here tomorrow it’s all ready to slap back in.
0236740A-DFAA-4C89-AF54-00553BC31330.jpeg
FF8BDB5B-4560-4BAA-900B-35928CAC618A.jpeg



All in all not including removing my battery etc i spent maybe an hour, and next time should take 20-25 minutes total.
Pull drain plug with small bowl under it. Pull fill plug, let completely drain. Put the drain back in, then fill with drive fluid, fill until it wants to drain out the fill put plug in and done. (Should be about 4-5oz of drive oil)
 

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Motoxxxloak

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View attachment 966738 View attachment 966739
Looking down at what i gotta do! Removed the battery box and prop mount just for ease of space.
View attachment 966740 View attachment 966741
Definitely was time for the impeller.
View attachment 966743 View attachment 966744 View attachment 966745 View attachment 966746
Marked drilled with 5/16” drill bit. Drilled real slow and at about a 70* angle so when i got in minimal shavings would hopefully get in. Slight hit with the bevel bit to clean the outer edge. Then i ran my 3/8-16 tap in. Blew out from the fill out the drain into a paper towel was happy to see no shavings come out. View attachment 966747
Test fit all was perfect, except realized that the plugs needed polished. View attachment 966748
Now when the new impeller gets here tomorrow it’s all ready to slap back in. View attachment 966749 View attachment 966750


All in all not including removing my battery etc i spent maybe an hour, and next time should take 20-25 minutes total.
Pull drain plug with small bowl under it. Pull fill plug, let completely drain. Put the drain back in, then fill with drive fluid, fill fill it wants to drain out the fill put plug in and done. (Should be about 4-5oz of drive oil)
So, there is a way to drain it without taking these steps but it is painfully slow? I know we talked about this and not sure if the 525 pump is the same as the one I did many years ago.
 

02HoWaRd26

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So, there is a way to drain it without taking these steps but it is painfully slow? I know we talked about this and not sure if the 525 pump is the same as the one I did many years ago.
Yes you can suck it out with a syringe or you can remove as i did, then roll it over to drain slowly.
This way also makes easier as the fill acts as a vent, no vent and 90w makes for a slow drain.
 

FROGMAN524

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Was there fuel in your gear oil for the pump? Just ordered these yesterday from Hardin marine on recommendation of Mike from Marine Design Corp who design them pressure equalizers.



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02HoWaRd26

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Was there fuel in your gear oil for the pump? Just ordered these yesterday from Hardin marine on recommendation of Mike from Marine Design Corp who design them pressure equalizers.



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I had read that a lot of people do find that issue. This was my first with this style pump and luckily no fuel in mine.
 

FROGMAN524

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Just got these in today.

IMG_4334.jpg



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FROGMAN524

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It’s supposed to equalize the pressure between the pump and the gear case. Keeps the pump from failing snd pouring fuel into the case. I believe you have to drill and tap on both sides.


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Duck'ed_Up

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I had read that a lot of people do find that issue. This was my first with this style pump and luckily no fuel in mine.
It is a common problem! My boss has a 42 fountain with 700s which have harden 2 stage pumps. Needless to say the pressure pushed the oil out and ruined a mechanical fuel pump and main shaft on his two stage. Now both have the vent tube kit from Hardin


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02HoWaRd26

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It’s supposed to equalize the pressure between the pump and the gear case. Keeps the pump from failing snd pouring fuel into the case. I believe you have to drill and tap on both sides.


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Are you doing the install yourself? If so it’d be awesome to see the whole job, and if you decide to do the drain job the part number for the drain plugs is (10-79953Q), and you’ll just need the drill bit (5/16”) and then a tap (3/8-16)
 
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