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Technical: Isuzu 42 Servicing Info

Posted by indigodream on 8 January, 2013

This is my reference page for the parts I regularly need for servicing the engine and also somewhere for me to store copies of the engine manuals etc.

So you know which engine we have here is a photo of my engine bay (after a re-paint so unusually clean!)


I used to buy filters from a motor factor in Croydon which has now closed 😦 so some of the references are tied into their references. Nowadays I tend to buy genuine parts from Kings Lock Chandlery (they do online also) and OEMs from inline filters – links below.

These are my parts lists:

Air Filter:  Isuzu Part No. 100066-4LS OEM References:  FRA CA5315 or Cooper AG 294,  An equivalent seems to be a Reisse 46100020.

Supplementary Fuel Filter:  FRA C1191PL or FDE-HDF296, I fancy the second is better?

Main Fuel Filter:  The manual say Isuzu Part No. 897172-5491. Last time my engine was serviced it was by the excellent Neil Coventry he put in an Isuzu 5876100220 so I suspect that the part number has changed. Finding an OEM equivalent is interesting.

Main Fuel Filter OEM References:either Baldwin BF954 or Donaldson P553240 or Fleetguard FF5030, Filtron PP944 or Mahle KC5. Note these are all a fraction longer then the Isuzu part so slightly more awkward to remove with my style of filter wrench.  This site cross references the Isuzu 8971725491 with an Isuzu 8941329471 and that in turns leads to a Fleetguard FF5394 which is shorter, same length as the Isuzu so I have ordered one, look out for us anchoring somewhere. Update: The FF5394 looks almost exactly like the Isuzu filter, works well, no issues so far. Note to self: I have photos to post.

Oil Filter Isuzu Part No. 894456-7412 OEM References: FRA PH6811 Mahle OC205

Correct oil is 15W40 CC grade which can be hard to get hold of. Supermarkets sometimes have it, motor factors often have Comma 20W50 CC Engine Oil, can be really cheap but outside the scope of what Isuzu recommend – see page 26 of the Isuzu manual. There is an excellent Morris oil best bought from that lovely garage in Wheaton Ashton.

Chandleries stock genuine Isuzu parts but take care, the genuine parts are always expensive but not all chandleries are the same – did not note down prices but I think Kings Lock in Middlewich had pretty competitive prices for Isuzu branded spare parts (and they are nice people). Hint: When shopping in a chandlery just cover your eyes as you put in the PIN number, puts the shock off for a month or so.

My last shop from inline filters in December 2021 had these prices but all are plus VAT ie add 20%:


1 ea. FFR-CA5315 FILTER-Air(Round) £6.52
1 ea. FDE-HDF296 FILTER-Fuel(Can Type) £3.90
1 ea. FBW-B1425 FILTER-Lube(Spin On) £8.84
1 ea. FFG-FF5394 FILTER-Brand Specific(Fleetguard) £4.73

My “Library” as it is so far:

The correct parts – click parts-list

HMI engine manual – click hmi-isuzu-manual

PRM gearbox manual – click prm-manual

Isuzu Canal boat leaflet – click Isuzu_Canal_Boat_leaflet

Isuzu Pricelist – click Isuzu_pricelist_202009

Isuzu dealer list – click Isuzu-dealer-list-20010608

Isuzu Engine Manual – click isuzu_4le1_opm

Isuzu Workshop Manual – click Workshop-Manual-Isuzu-4lb1-4lc1-4le1-Gb

CAV Filter manual – click CAV Filter Manual

Other bits from the boat:

Haztec Manual (new type sensor): Click Haztec Instructions

Flojet servicing instructions: Service PAR-MAX 31xxx and Flojet Quad

I should start a list of useful web sites if only so I don’t have to resort to google when I can’t quite remember them. I will add more later but whilst I think about it here are two:
We needed to get our alternator sorted so used the excellent A&A Auto-Electrical in Croydon to check it out for us, their diagnosis was cream crackered and they put us onto these people who could get us a new alternator at a cracking price next day: They also do starter motors . . . .
This was a useful site for odd Isuzu Parts but website has been down for a while:
If you have any useful sites to add or part numbers for obscure things eg starter solenoids please do post a comment.

21 Responses to “Technical: Isuzu 42 Servicing Info”

  1. Capt Ahab said

    Yes but what about Beta parts. The Fram parts from Midland Chandlers are equally pricey and there must be cheaper generic alternatives.

  2. indigodream said

    No idea! Send me your parts list and next time I am in there I will leave it with them and get them to look up alternatives and a price, I think they do mail order? Otherwise I think Joe on Yarwood has been into a car parts place somewhere on his travels and may be worth talking to as I think he got an amazingly good deal for Beta filters.

  3. Alf said

    I use Baldwin ( there is a good comparison search, simply type in what you have & their alternative is then shown.

  4. Rob Wheatley said

    Filtermania Stafford takes some beating, does national postal service too

  5. Andy said

    Hi there what is the largest size prop I can put on my boat I’ve got a Isuzu 42 with a prm 150 gearbox many thanks Andy

  6. indigodream said

    Hi Andy

    We have an 18×12 driven by the same gearbox and engine as yours and really happy with the combination. We can’t get any more than 2000 rpm so I think that is as big a prop as we could have. If you are thinking that you want a larger prop then check the clearance to your counter first.

  7. James Maccuaig said

    Hi iv`e got a leaking injector pump on a 4lc1 any one know the generic part no of this pump.

  8. liz said

    Oh font of all knowledge….it appears I need a new stop solenoid…have you any idea what the part number is?…I can get someone to come and change it for me…but obviously I need to order one first. HELP…many thanks..your site is brilliant for a boater with no manual or knowledge! Liz

  9. indigodream said

    Hmm worrying that you need a new stop solenoid, seems that you are not the only one! I asked the real font of knowledge, Neil Coventry, who texted me that the last one he got was from EnginesPlus and cost a fortune, much cheaper to fit a stop cable! Some else has written about being quoted £400.

    The only thing I have seen worth trying (other than a main dealer) is a company called JGsupplies Tel: 07976 960921 but I was a bit thrown as the website is something else – worth a phone call as the quote a cost of £60 BUT not an original part. Also try Quayworks as the link above. Please leave a comment if you get anywhere.

    This is how I got there:

    There is a thread about stop solenoids on CWF here: which is useful but also confusing. Someone reports the part number as MV1-77 897209-1140. This tallies with the number in the HMI manual so seems right. When I googled for Isuzu 4LC1 solenoid I got a different number. That said there is also a useful link to this ebay page: which gives the same number as my googling but it is an MV1-81, is it the same, no idea but as there is a phone number in the UK I think it is worth a call.

    Sorry I can’t be of any more help.

  10. Mark said

    Just bought a narrowboat with one of these engines fitted,
    Most helpful.
    Thank you.

  11. Andy Metcalfe said

    Big thanks for all the info. Just bought a low hours marine unit and want to replace the filters. Any issues with the air inlet on the 4L.42 marine unit? It seems very restricted being so close to the heat exchanger.

  12. indigodream said

    Have you got an older model perhaps? Air filter sits on top, will add a photo to this page

  13. Andy Metcalfe said

    I can’t add a photo but there is no room for an air filer. The inlet is a disc of metal with holes in, between the rocker cover and the heat exchanger. The paperwork I have shows it as being bought new from Southampton boat show back in 2008 but has only done 60 hours. It is now installed in my Colvic Atlanta 32 motor sailer and runs okay. If you email me I can send you a photo.

  14. murray Roberts said

    Indigodream your Isuzu info is so useful its saved me hours of searching, do you know where I can buy the rubber grommet that fits the air filter unit to the rocker box I’ve and Izusu 42. Many thanks again for creating this resource.

  15. indigodream said

    No idea! Engines Plus or an Isuzu Engineer? Otherwise original filter was a Cooper AG294 which seems quite common so a motor factor may be able to work out a part number? Try

  16. Murray Roberts said

    thanks no joy there i will have to make some thing

  17. Cap'n Ed said

    Very helpful Rgds Ed
    PS How you keeping? Dodging the Covid bullet?

  18. indigodream said

    Is there a bug going round? Is that why I keep on seeing Lt. Gruber on the TV?

  19. clive hares said

    I don’t know why but some Isuzu 35s have a proper air filter and some just have the silly disc mesh. mine has the latter which i am not comfortable with so i have acquired a suitable size filter from a car scrappie and then i am going to remove the rocker cover, blank of the existing inlet and cut a new one in the top, then make something to fit the rocker cover to the filter. i will also adjust the tappets while i am at it, the manual says to adjust every 1000 hours and it doesn’t look like the lid has ever been of with 52000 hours on the clock.

  20. i need to replace the head gasket on my Isuzu 42 (about 15 yrs old). do you have any useful information on this?
    i looked at the workshop manual for the 4L series but dont know how similar they are

  21. indigodream said

    I would have thought a 15 year old one was a 4L?
    Have you tried the Isuzu Marine engines owners group on facebook? Worth joining as there are some really knowledgeable people there:

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