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carb rebuild

by betty boop » 20 Apr 2015, 11:21

How easy is it to rebuild the Mercrusier 3.0l carb? I have a hot engine restart problem (wont idle when hot) only runs when rev'ed to 1500, I read on the interweb that as I've had fuel in overflow pipe, it may be a sticky float.

Looking at You Tube does nothing but confirm my fears that Carbs are black magic art and best left well alone. but if the rebuidl kit is mostly gaskets can it be that hard?
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by mlines » 20 Apr 2015, 12:21

We did ours last year.

We had a series of issues as we de-winterised. At first there was a dead spot as we throttled up to the plane which then became a dead spot between idle and flat out.

In terms of a carb rebuild, it is pretty straight forward. It is just gaskets. I had no problems taking it apart and cleaning it. The only issue I had on the gaskets front was that a "full carb gasket" kit does not contain the carb to manifold gasket (and guess which one is completely destroyed in the dismantling process.)

If you have taken car carbs apart then you will be fine.

The only problem I had was that we never really found a problem. Flat and dead spots imply a blocked jet (its a multi jet carb) but we didn't find one. The carb did have rubbish in it (in the form of small black flakes) and I did have a couple of attempts at clearing this (ran ok for short while and then re-occurred). Basically I just kept cleaning until it worked ok again. The only possible conclusion was a collapsed fuel filter which I found.

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by mlines » 20 Apr 2015, 12:23

PS we had a "wont idle when hot" issue when we first got the boat which was a "TKS" issue (Turn Key start) - effectively the choke. You can test this when you dismantle the carb.
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by Ianfs » 20 Apr 2015, 13:55

It is dead easy although I took it all apart and then I had help from Ed with the rebuild but, I have had it apart since.
I've just got the new Power Piston so am about to put it back together.

Best to buy a rebuild kit, they have instructions too. I'll also mail you some photos of mine, although its a different carb they are pretty much the same.

If the tube you are referring to is the Tell Tale to the fuel pump, then fuel in this is normally a pump issue. However if she doesn't idle but revs instead that wouldn't make sense.
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by betty boop » 21 Apr 2015, 08:08

mlines wrote:PS we had a "wont idle when hot" issue when we first got the boat which was a "TKS" issue (Turn Key start) - effectively the choke. You can test this when you dismantle the carb.


thanks Martin
The more I read the more I suspect a TKS problem - what did you do to fix that? I havent investigated fully but Im led to believe its a 'module' on the carb which is replaced? or can it be repaired (assuming Im barking up the wrong tree.

& where did you get ur rebuild kit from?

thanks Ian
you're right but the fuel had decomposed into green slime, so was there for quite a while I'd guess. After cleaning it hasnt returned (last season) so I suspect that fuel pump isnt an issue (and will be 3rd on my list of checks).

Mandy's 15 yo son takes carbs apart for fun but they scare the c'p out of me for some reason, looks like I cant avoid it so will take the plung and give it ago :? :shock:
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