Mercruiser 4.3 - Alpha One

[searayuk]

Hi all

I'm trying to breathe life back into a 4.3 v6 from around 89-90 with a Mechanical fuel pump and TB IV ignition. Think I've sorted the ignition and wiring after sourcing replacement parts from the US and repower marine.

The next thing is fuel supply. My mechanic wants to replace the mechanical pump with an electronic one, but I'm reading posts against the idea. I also realise that I'd need an oil pressure switch (which would have to be taken off t piece at pressure sensor) and would need to ensure the pump is correct flow and pressure. There are a few discussion threads about this, but hoping there are a few U.K. based opinions!

Has anyone done this successfully? Thanks.




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[Ianfs]

Is there a reason he wants to replace the pump? When I had the carb off mine recently the mechanical pump was chucking out fuel like a fountain.

[stingrayfan]

If you need a second opinion, call Kings Marine in Chertsey. Good guys.


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[searayuk]

He wants to replace it with a more modern electric pump, as the mechanical isn't looking in the best condition and someone has effected a poor DIY repair on it previously. I can lay my hands on another one easily, so if the general consensus is to stick with the mechanical OEM version then I can go that route. He also mentioned about it being not very accessible if it ever failed...


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[Ianfs]

He wants to replace it with a more modern electric pump, as the mechanical isn't looking in the best condition and someone has effected a poor DIY repair on it previously. I can lay my hands on another one easily, so if the general consensus is to stick with the mechanical OEM version then I can go that route. He also mentioned about it being not very accessible if it ever failed...

There are fors and against.

If you've got a marine engineer working on it, I guess he should know what he's talking about and advise accordingly, plus if its had a botched repair it'll be because the mechanical pumps are not fixable, they have to be replaced. A lot depends upon what the internal parts look like i.e. the cam which powers the pump.

[searayuk]

Ok so I bought s cheap elec pump to test with and my mechanic has got the old Merc turning over and firing. Needs some tuning but so far, so good. It wouldn't fire previously and it turns out the dist was 180 degrees out! No wonder there were serious flames seen at the exhaust - seems likely the sparks were firing on the exhaust cycle!

Anyway, back to the original question - so I've read quite a bit on the elec pumps vs mech now. I understand the need to install oil pressure switch to cut the flow if the engine dies. We are also looking at installing fuel alarm in the bay just be to extra safe.

My mechanic isn't a marine engineer but he is very competent and armed with the right info he is happy to assist with this project. If we need to involve a marine engineer at any point we absolutely will, but for now we're getting the engine built up ready to drop in.


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