Are you talking about the kind of thing usually found on an outboard? Never heard of it being installed on an inboard.
On an outboard I believe it's typically installed between the external fuel/water separator and the motor, although with the strength of the fuel pumps on modern four strokes these primer bulbs have been rendered largely unnecessary- I have an F200 Yamaha and there's no need to pump, the motor pulls fuel just fine on its own.
Squeeze Bulb Priming on Diesel Powered Boatsby Tony AthensOur Politics here to help understand "Squeeze Bulb Priming". For sure, I have been using Squeeze Bulbs with diesel fuel for well over 20 years now. I still have not seen one rot or fail externally, so to me they have withstood the test of time in the field. I still get feedback from those who do not have any experience with them worrying about "this and that". All I can say is they are used and approved with gasoline in all types of applications, so to me, they must be safe, regardless if ABYC or some surveyor has an issue with them. If I worried about those things, I just as well quick thinking for myself and go back 20+ years in my work.
As to flow and restriction: If you use the typical 3/8" variety squeeze bulb, you can install them in series ( if you like, with no valves or "T's") and not worry about any undo restriction on most mechanical diesels up to 250 HP or so with rotary type fuel injections. On engines with inline or CR "Bosch or Nippon Denso" type fuel systems, I'd use either a single semi-isolated system or a fully isolated system and 1/2" - 5/8" line for the main fuel system as much as possible. With the fully isolated system, you can feel 100% comfortable even using 3/8" clear vinyl hose for fuel line so you can "see" the bulb do its job. Also, when testing fo air, you can allow all the fuel to go through the clear hose an see if you are sucking air someplace before the bulb.SIMPLE MULTI-STAGE FUELTRATIONTM SYSTEM WITH SQUEEZE BULB PRIMING
PRIMING SYSTEM CAN BE INSTALLED BEFORE OR AFTER THE FILTERSNothing I have used does a simpler or better job than the old fashioned and simple "Squeeze Bulb" as to priming the system or using it as a tool to check for other fuel system problems. I'd love to see a 1/2" ID unit, but I have not found one yet...Simple & Effective Isolated Squeeze Bulb Priming System using Clear Vinyl Hose
I think the value of this type in installation is 100% obvious to most anybody that has gone through priming a diesel engine in a vessel from both the practical and safety standpoint when you have to get your engine running - In other words, I suggest you just forget about the politics of "squeeze bulbs" that come from ignorant boaters and the typical wharf rat that thrives on "dock talk".
For those who are squeamish about using clear vinyl tubing for this part of the system (because "no one" has approved it) please, you have my blessings, or feel free to substitute CG A-1 fuel line for the squeeze bulb hoses. Personally, I'd rather watch my fuel prime, and understand realize the limitations of clear vinyl tubing used as a temporary diesel priming hose, and then just replace it if needed for about 2 bucks every few years when & if needed - Your call !!Tony Athens / Seaboard Marine - Jan 09
These are an absolute must! I put one in years ago because the boat was constantly plugging filters and the tiny primming pump on the engine wasn't cutting it. I will never own a boat that doesn't have this set up again. They usually only come in 3/8" but with a couple isolation valves you can still use larger size fuel hose to feed your engine. Theres no easier way to fill a racor and get fuel back up to the engine.