advice wanted on injector pump + pre-pump/primary fuel pressure increase

Hi folks,
I have an old 1980s Volvo Penta diesel engine 6cyl fitted with an 11mm Bosch Zexel injection pump. The turbo on the old girl is something out of a horror movie and makes a pathetic 165hp. I wish to fit a variable vane turbo I have and I need to increase fuel to suit. Looking to achieve around 240hp which is well within the range of the turbo.
The zexel pump has no lda. I want to increase fuel in a way that will provide the top end fueling I need but when the boat is at cruise it’s still going to be fuel efficient. I see three possible options,

1. Fit an alternative Zexel pump with an lda
2. Try to find an Zexel lda pump top that I could retro fit to my existing Zexel pump (possibly from a damaged pump)
3. Attempt to pressurise the fuel prior to entry into the fuel pump using an electric pressure pump and variable pressure regulator

It’s the third option I’m keen to talk to people about. I’ve heard of people trying this with mixed results. For light increases in pressure I’ve heard success. Larger increases see seals popping out of the pumps etc. I heard of one guy who modified the pump seals to take the pre-pressure increase and managed to get this to work for him. It seems like an economical way to increase fueling and have control over rpm via the regulator.
Does anyone have any experience with this or advice? Thank you

It doesnt work. For fuel economy LDA doesnt matter, it is only to reduce transient smoke. So just turn the screw and be happy with it.

Leiffi said:

It doesnt work. For fuel economy LDA doesnt matter, it is only to reduce transient smoke. So just turn the screw and be happy with it.

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Hi Leiffi,

Thanks for the reply. You say the lda is only to reduce transient smoke? That's true. The smoke however is due to an incomplete burn. The fuel to air ratio is too great. You get cylinder cooling and incomplete combustion. As an lda turns down the governer it has to increase fuel economy?

Jimbobtx3 said:

Hi Leiffi,

Thanks for the reply. You say the lda is only to reduce transient smoke? That's true. The smoke however is due to an incomplete burn. The fuel to air ratio is too great. You get cylinder cooling and incomplete combustion. As an lda turns down the governer it has to increase fuel economy?

Click to expand...

No, diesels regulate boost with fuel , so give it less fuel you get better A/F ratio.