bertram31.com

Bruce (or other knowledgable faithful),
I have a vapor locking problem on hot days. In the colder fishing season, I have no issues. In the July heat, if I shut the engines down, it takes a few hours before I can restart them. My engine manufacturer says the best remedy is to install booster pumps as close to the fuel tank as possible. He is reccomending a Carter Marine type pump that puts out 7psi max. I know my Racor's will handle 7 PSI but Gary at flo-Scan did not want to comment on putting any pressure on the sensors. I have very little room to work with between the flow-scans and the engines without redoing the plumbing of the entire boat.

Here is how my boat is currently plumbed. Fuel pickup, fuel shut off valve, 4 feet of 5/8' fuel line, Racor spin on filter with flo-Scan meter directly attached. 2 more feet if 5/8 line running to the engine then to a Mercruiser / Siera type spin on filter on the side of the engine. From there, the fuel gets pumped into the fuel rails by the fuel injecter pump (which is the only pump I have been using thus far). From out of the fuel rail, the fuel goes thru an exchanger where it is cooled and then back into the Mercruiser type filter on the block.

Bottom line question, If I could live with slight variations in flo-scan readings, is it save to put the booster pump before the flo-scan meters?

By the way, special thanks to Mikey who let me hang out at his place in Irvington, VA while I waited for my engines to cool enough to start.

Chiles

Chiles,
Most all manufacturers have gone with a dual pump system, one to pull the fuel from the tank to the engine, the other to boost the pressure for the injectors.

It sounds like you have the early Merc injection system which was prone to vapor locks.

An addition of a Carter vane style pump would help.
You will have irratic readings from the floscan but I would mount the pump after the fuel filter and floscan sensor.

There is a small and fine screen in the pump that will clog without a filter before it.

As an example, Marine Power mounts both pumps on the engine.

One thing I have done to help vapor lock is to insulate all exposed metal fuel lines.

Bruce,
These are the Mazda Rotary engines and have (for the most part) a fuel system very similar to Mercruiser because he uses their filters and fuel coolers, etc. I guess it only makes sense that I would inherit the same issue. Needing a pre-filter before the pump gives me all the reason I need to redo the way I installed the fuel lines. It's not going to be easy, but doing it right seldom is.

Thanks for the advice.

Chiles

Bruce,what material do you use to insulate the the metal fuel lins with, thanks Russ

It's not going to be easy, but doing it right seldom is.

Amen brother.

Russ,
I use a heavy wall fuel line most of the time and anywhere the line has a clamp to secure it, I insulate that to reduce heat transfer from the block.
Also depending how the high pressure pump is mounted, I may insulate the mounting or relocate it.