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Discussion Starter · #1 ·
I have a 2.5L Mercruiser inboard w/Alpha I drive I think. Here is my big problem, I start my boat amd most of the time it does actually fire. If I am in the water and put the throttle in forward the boat stalls. If I give it a lot of gas it revs up and then dies. I have no clue. I am not sure if it is actually firing all 4 cyl. or not. I am sure that it fires on 2 and 4 because will ideling, which it does alright, I take the wires off and it sounds like it is skipping. Now with 1 and 3 there is no change in sound. No begining this year I bought new spark plugs, and wires. Now the old wires were all different lengths, and the new ones, 1 and 3 are the same length and 2 and 4 are the same length. I was wondering if that has some thing to do with it. I need as many suggestions. I did put in a new fuel pump and I was also wondering do I has to do any adjustments when that is put in. I need help for this labor day weekend. Please any advice would be a miracle.
 

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You shouldn't have to make any adjustments just because you changed the fuel pump. If you pull the plug wire off of ANY cyclinder on a 4 cylinder engine while it is idleing, you should definitely notice a miss. Is it possible that you screwed up the plug wires when you changed them? Look at your firing order and make sure that the wires coming off of the distributor cap are going to the correct spark plug in the correct order.
 

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I think you're going to need some hands-on help from someone, don't believe that talking on this board is going to help you much. If you motor is idleing smoothly and you pull a plug wire it should definitely miss. You say it doesn't, that doesn't add up. Also, the revving up and then dieing sounds more like a fuel problem - starving for gas. Also, Mercruisers have a shift interupter switch which grounds out the spark for an instant when you shift into and out of gear - if this is out of adjustment it could cause the stalling when shifting. All in all, you either need a mechanic or a good service manual.
 

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Could it be that the 3 & 4 wires are reversed (going to the wrong plugs)? Have you tried swapping them?

It's hard to believe that motor would idle on one cylinder (if 3 & 4 are reversed) and you pull 2 off, replace it, then pull 4 off.

Stranger things have happened.
 

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Discussion Starter · #8 ·
I replaced the spark plugs again. before I put them in, I sprayed a little WD-40 to clean up a little rust, in cycl. #1. And I also tore down my carb and spent time cleaning it. Then I also adjusted my throtle cables. So I can't point the finger at just one thing, but I still believe it to be the plugs. I even bought the cheap ones at Advance Auto, $1.24 per plug.
 
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