Warning! New filter system on new Yanmar engines is Bad!

eherlihy said:

The metal cup is actually called a "heat shield." I believe that they are an ABYC requirement - too lazy to look it up. I don't have one on my boat, and they are STUPID expensive (like $150) for a $2 piece of stainless.

Click to expand...

I looked through the ABYC standards. The two most pertinent standards are H-33 "Diesel Fuel Systems," and P-4 "Marine Inboard Engines and Transmissions." NO MENTION OF A SHIELD REQUIREMENT FOR THE FILTER BOWL.

There IS a USCG requirement (USCG and EPA Compliance Guidelines; Fuel and Emissions) for inspected vessels that every part of the fuel system must be able to withstand 2.5 minutes of exposure to a heptane fueled flame. The temperature within one inch of the (bottom of the) component under test must reach 648ºC at some time during the test (now you know why these shields are so close to the filter bowl).

The need for the shield, which could hold fuel, to deflect the heat makes the use of it seem like a BS requirement to me.

There is also a requirement that any fuel pump be located within 12 inches of the engine, with the only exception being if the pump is used to move fuel between multiple tanks. I don't meet this requirement either.

Mark ....
Sorry for your problem.

The 'best' way to deal with this and to prevent fuel gremlins from exposing themselves at the exact WRONG time during 'serious' travel (ie.: crossing a bar, or entering a busy port channel, etc.) is to install an independent fuel recirculation polishing system that also constantly delivers to an independent 'day tank' of 1-2 gallons to a small 'day tank'. This will enable when SHTF of the fuel system, one can quickly 'open' the contents fo the day tank directly into the lift pump and keep going for an hour or two with a high probability of ultra clean fuel .... enabling one to get to a safer place and then assay the system properly.

The recirc system (for an engine of your size/hp) is simply a 10" long by 2.5" diameter (industrial type - steel) filter housing, an independent 12vdc Walbro-type pump sized to totally 'turn over' the entire contents of your fuel tank at about *2-3 gallons per MINUTE* per 100 gal. of tank capacity. Retention size of the recirc. filter should be 'open' to allow for the *largest possible flow rate* ... about twice the retention µM of your 'main'/workhorse fuel system filter (usually a 10µM). That ~20µM filter in the recirc. system statistically will deliver the particle count to MUCH less than 10µM as it will constantly deliver the fuel over and over and over through the independent recirc. filter (from the tank, pump, back to the tank ... and day tank) any time the engine is 'on'. My current recirc. pump system using a 15µM depth type spun bond polypropylene filter sometimes maintains 'sub-micronic' levels of fuel particles.
The day tank (1-2 gallons) arranged high in the engine compartment, and with LARGE as possible hose/tubing to prevent flow resistance, so that no pumping needed to deliver to the lift pump .... all 'work' done by gravity, once the bottom 'kock-valve' plus atmospheric vent valve of the day tank is opened. .... then you'll have about 1-2 hours of run time before you 'have' to find the problem. A clean-out 'hand hole' needed on the day tank for routine inspection and cleaning of bacterial/fungus.

Racor offers self contained recirculation polishing systems for the LARGER boats ... youre required to sign a mortgage. Simply follow the Racor advertising sketches and build your own ... for a minimum constant 'turnover' of about 1-2 gallons per minute per 100 gallon tank, at ~15-20 µM using a 'depth type' cheapy filter element and 'steel' filter housing - Home Depot stuff.

FWIW In the tropics or far 'outports' when I pick up bad fuel ... usually very fouled with tank wall crap from delivery barges in heavy seas ... I can 'usually' return to visually clear** (less than 5µM particles) in about an hour on a 100 gallon fuel tank ... sometimes using several depth filters.
FWIW2 - If you put fuel into a clear glass container, hold it up between your eyeball and the sun .... any denoted 'haze' indicates particles greater than ~5µM. I usually visually test all fuel going into my tank ... using a 6 ounce clear water glass.

FWIW3 - the absolute simplest remedy is to install a 2 valve block and bypass 'around' all the Racor train, etc., and when the engine stumbles simply open the block and bypass to operate 'briefly', with NO filtration, until youre in safer waters - "chancy" but will work 'briefly'.

Another suggestion is to install a 12vdc vacuum switch assembly wired to an 'alarm' to your main fuel system - one wired vacuum switch between the lift pump and the so-called primary filter. The differential pressure set point should be set for 10-15% lower than the RAcor's operating CHART (flow rate in GPM vs. differential pressure - psid across that filter) with your engine running a 100% rpm / WOT. Youll also know (by alarm) WHEN to soon change out your main fuel system filters. If thats too much, put a simple vac/pressure gage between the filter train and the lift pump ... and routinely monitor it with the engine running at WOT ... simply check now and then if the vacuum gage is showing a noticeable increase or the correlation to ∆P on the Racor *flow vs. ∆P chart* is now at 90% of the required fuel flow to keep your engine running at wide open throttle - WOT

Of course, you should be 'dosing' with Biobor™ for antibacterial and antifungal control.


The problem with small pieces of 'crap' ... chunks of bacteria (mini-strings)/funguses/plastic etc. debris is that they offer 'sites' where even teeny particles can begin to 'bridge' onto the small piece of crap and can set off an exponentially 'fast' full blockage of the fuel system. In industry, any foreign object at greater than 1/4 the diameter of the diameter of the tube/hose can cause a rapid complete blockage .... as most of these particles in most liquids are electronically surface charged ... they 'clump' together.

hope his helps.

Pictures are better than words. This is from ~1995-2008. Component part numbers need updating, etc.

Other suggestion, that 12vdc 'bleeding' pump in the upstream probably should be replaced with a 12vdc full-on diaphragm-type pump plus 3 valve block & bypass ... as a backup for a failed engine lift pump - not cheap.

... Plus, that pump in 'pressure feed mode' and an emergency scenario will add about 6psi to the fuel delivery system ... you'll realize the value of adding 6 psi to the fuel system when you carefully scrutinize your Racor filter's flow chart diagram (GPM per PSID) ... more additional flow through a partly clogged filter !!!!!
Note: pressure feed is for fuel systems monitored constantly by a marine engineer, as if you have any piping, etc. failures with pressure feed on the system, you are vulnerable to filling the bilge and overboard in a hurry. All pressure feed systems should have double flared connections (NEVER with 'compression' fittings), and well rated pressure service design for the entire fuel system .... plain rubber hoses are strictly 'verboten'. Pressure feed systems rarely need air purging or 'bleeding' to affect a 'restart'.

FWIW - the common fuel system design on recreational boats are specifically designed to FAIL EASILY ... any time there's a fuel system failure, a vacuum feed system automatically 'sucks air'; and, instantly shuts down the entire fuel and engine system, usually with no oil leaks into the bilge, etc.