1996 GT-40 power issues

[Bobby]

I was finally able to take out the boat (1996 Sport) this last weekend and experienced a couple of of issues:

1) Last year I was able to hit 44mph, then after winterization/dewinterization and a clean flame arrestor, I dropped to 40mph (virtually empty boat).

2) The hole shot is bad. Really bad. It takes its sweet time getting to 20mph, but after that the throttle response is fine.

3) I have a knock on the driver's side of the engine, but I have new plugs/wires/cap/rotor.

4) Sometimes the engine dies after being put in gear.

My questions are what started this and where do I begin to fix it?

[M3Fan]

RE: 1996 GT-40 power issues

Let's have some more information about the knock. That could be bad. Is it present at idle?

[Bobby]

Re: RE: 1996 GT-40 power issues

Let's have some more information about the knock. That could be bad. Is it present at idle?

Yes.

[tadelfio]

RE: Re: RE: 1996 GT-40 power issues

Bad Fuel???

[DanielC]

RE: Re: RE: 1996 GT-40 power issues

Is it a mechanical knock, or a preignition knock?

[Bobby]

Re: RE: Re: RE: 1996 GT-40 power issues

Is it a mechanical knock, or a preignition knock?

It goes away after I give it some gas, it that's what you're wondering, but when it idles the knock is pretty prominent.

[M3Fan]

RE: Re: RE: Re: RE: 1996 GT-40 power issues

If it's a mechanical knock, like a hammer banging on the engine, well, the last GT40 I heard with a mechanical knock needed to be replaced completely from a collapsed piston skirt. With a stethoscope you may be able to pin down where the knock is coming from.

Since you recently replaced a bunch of stuff that adds a whole handful of new variables as well. Could a spark plug just not be fully seated?

[Bobby]

Re: RE: Re: RE: Re: RE: 1996 GT-40 power issues

If it's a mechanical knock, like a hammer banging on the engine, well, the last GT40 I heard with a mechanical knock needed to be replaced completely from a collapsed piston skirt. With a stethoscope you may be able to pin down where the knock is coming from.

Since you recently replaced a bunch of stuff that adds a whole handful of new variables as well. Could a spark plug just not be fully seated?

when you put it that way, it doesn't sound like a hammer hitting, more like no fuel ignition. the engine doesn't smoke or anything and doesn't appear to have any other majpr issues. The fuel tank was empty at the end of last season and i put a fresh 12 gallons in when I took it out.

[M3Fan]

RE: Re: RE: Re: RE: Re: RE: 1996 GT-40 power issues

Unseated plug wire, bad plug, bad wire?

[Bobby]

all plugs are seated properly and not fouled. the wires are on firmly and the cap and rotor are on firmly as well. There doesn't seem to be anything wrong with any of that stuff.

Is it a possibility that my high pressure fuel pump is bad? Clogged injectors? I noticed some corrosion around where various wiring plugs in near the top of the engine, could that be it? I'm stumped and I don't really want to start replacing things one by one to see if that helps.

[DanielC]

An engine needs three things to run. Compression, ignition, and fuel. The ignition and fuel are controlled by the engines computer. With a few basic assumptions. The computer assumes the fuel pressure is correct, and if it is not, the computer has no way of knowing that.
The ignition timing is also controlled by the computer, and usually does not need adjusting.
The knock, and lack of power concern me. With your engine, I would first do a compression test. You need a compression gauge, and you need to disable the ignition by removing the wire from the ignition coil to the distributer, and grounding it, remove it from the center post of the distributer cap. If you do not ground this wire, the high voltage will find some other way to ground, and may damage something. Remove all the spark plugs and crank the engine with only the compression testor in one hole.
Listen to each cylinder for unusal noises, or knocks.
If all the cylinders have good compression, within about 10% of each other, put the plugs back in, and run the engine with one spark plug wire grounded for each cylinder, and see if you can find what cylinder has the knock.
If one cylinder has significanly less compression, or sounds a lot different with one spark plug wire grounded, you have a mechanical problem, and your engine may need major work.
Do the above tests, and post again, with more info.
Sorry I cannot give you more info, but this is a hard one to diagnose over the internet.