1996 Ski Nautique 176 with GT-40

I recently bought at 1996 ski nautique 176 with a GT-40. There is a long story behind the boat but in short it set with the motor dissassembled for 10 years. I have put the motor back together complete rering kit with all new gaskets. Lots of new parts due to corrosion,
Besides building the motor from the beginning , I put the following in new.
New carter low pressure pump,
New walbro high pressure pump
new plugs
new wires
new fuel injectors,
new fuel and ecm relays
new vacuum lines
new hoses
new impeller
new battery
new map senso
new IAC censor
new fuel regulator
most of temp sensors and other sensors

Once all this was done, I touch the key and it fired right up-But it lopes RPMs go from about 800 to 1050. I have pretty much tried everything in all the forums I have put in on the lake and it will only run about 34 mph and about 3800 rpm and it it will get up and run but as it goes down the lake it starts to lose power. It starts very easily but just lopes and does not get up to the RPM's it should.

Anyone have suggestions?
Ted

I have check pressure and it is as shop manual states, while idling it is in the 31 range which is what the shop manual says. if you pull the vacuum line off, it goes up to 39 which is what the shop manual also says. It has a brand new ford fuel regulator.

Maybe there is a nest in the exhaust hose That would slow down an engine.

I remember a guy at Green Lake telling me that happened to him..

Just got through working on a 97 GT 40 it was the fuel injectors I had three that were bad I have five good ones left thanks Dave 815-953-1823

browningskir7 wrote: Fuel pressure under load stayed very consistent at 31psi.

If your quote is true, then you have a problem with your regulator.

At idle (lots of engine vacuum) you should have about 31 psi and as engine load goes up your vacuum starts getting worse and the regulator compensates by increasing fuel pressure to maintain the same driving force across the injectors.

At full throttle/load, engine vacuum is essentially zero and you should have about 39 psi to give the same driving force

In between idle and full load you'll have numbers that are in between the 31 and 39 ish values.

If you have the 310 page manual in the reference section here on CCF, look at pages 2B2 and 2B3 for some info.

A steady 31 like you say you have will give you running issues   

You can ignore the words about the fuel vapor separator, that's not a PCM thing, it was used by Volvo/OMC with their version of this engine.

Ok, here is one for the books and not sure ever heard of this before. Everything done as described above. Ended up talking to the mechanic who worked for PCM and built the first 10 GT 40's ever built. He first asked about the IAC as many of you had suggested.I told him I had changed it so then he asked if the timing had been set to which I replied yes. He stated again was the timing set correctly to which again I answered yes. He said just for kicks and giggles check it again.   So I was using a friends timing light and he happened to be out of town so went to Yes you guessed it Harbor Freight and got a 30 buck timing light. Took it home and the timing was way off. Reset the timing and the hit the start, it starts right up and the loping disappeared. Friend came home and got his timing light ( a very expensive one) and by it the timing is way off so it appears a bad timing light caused much of this.

But still got a slight problem. After fixing the loping the boat fired right up and in the driveway hooked to water hose RPM's went up over 5000. Put boat in water and it would only turn about 3200 RPMs under load and by the old airguide speedometer was running about 32 mph wide open. Did not appear to open up. Suggestions? Fuel related? Maybe a bad injector? Taking a break so looking for suggestions when I go back to work on it.

The one I used, made the loping go away and the mechanic I talked to state that the timing being not correct would make one lope. So with the new light it made the lope go away, but to satisfy your deep philosophical question after the I got rid of the lope and blamed it on the timing light, just for kicks and giggles, I hooked the bad light up to my 1977 ford bronco which runs like a top and check the timing. Again i could not even see the timing marks. So now I have the old light doing the same thing on 2 vehicles one which run great and had never given me any trouble. I am pretty sure the old light is not good. I haven't been able to get in touch with the PCM guy to ask the question, so I through it up here. But I do intend to ask him the same questions I have here once I can get in touch with him. Looked at plugs again and 2 of the plugs look to be running real lean (nos 2 and 4)-wondering about 2 of the injector.