stuck 3000 rpm max

[Excel23]

I have a 1994 Welcraft excel 23 with a reman 5.8 volvo penta(351w) bored 30 over and a 300 hp cam and an edelbrock performer intake. I have been battling trying to reach WOT since getting the boat on the water this year. First i had the Holley 650 carb re built and couldn't reach over 2400 rpm, did wires, plugs, cap rotor, battery, Alt. In short, everything is new. I recently bought an Edelbrock 750 carb and went with the lightest step up spring (blue) and unless i take the spark arrestor of the carb and use a cloths pin to hold the air plate open i am stuck around 2500rpm, with cloths pin i can eventually get to 3000 - 3300 rpm. If i push the throttle any further it is just dead, wont accelerate nor pick up speed. I have tried changing spacer plates, now i am wondering if a mech. secondary is the way to go since i don't make alot of vacuum at the higher RPM's.

 

[alldodge]

How did the boat do before the rebuild?

 

[Excel23]

The guy said all he did was rebuild the carb and it was fine

 

[alldodge]

Tell us more about what "the guy said"

Its a new to you boa, did you have the motor rebuilt or something else?

 

[Excel23]

It is new to me and I bought the re man. Came with heads timing..... 300 hp cam. I am having the identical issues with the brand new edelbrock 750 as the holley 650.

 

[Excel23]

The boat sat for 2 years with a cracked block and intake. I completely drained the furl tank and have replaced the fuel water separator several times and put a new mech fuel pump in it.

 

[alldodge]

In that case it might be over propped, what pitch is the prop?

Have you looked at the plugs to see if they re burning good, as in light brown or cream color?

 

[Bondo]

The boat sat for 2 years with a cracked block and intake. I completely drained the furl tank and have replaced the fuel water separator several times and put a new mech fuel pump in it.

Ayuh,..... Welcome Aboard,..... Are you examining the Contents of the take-off filters to see how much crap is comin' outa the tank,..??

 

[Excel23]

The plugs look good and I have nothing in the filter, even keep taking samples of the gas to check for water in it. I use ethanol treatment and heat treatment. I run the highest octane at the pumps. Edelbrock tech suggested the lightest spring after they told me to open my air flap with a clothes pin! Wicked technical!

 

[Excel23]

It is the stock prop as well

 

[alldodge]

High octane gas produces more performance "only" in a high compression motor. To use it in a motor that will run fine with 87 the motor has less hp. Low octane burns faster

We need something to indicate how the motor is running. A bigger carb will not produce more hp. You need a fuel mix of 12 to 1 in best cases. 12 air and 1 fuel.

The plugs look good right now and there is none of them showing anything but burning correctly.

The fuel looks good and no signs of an issue. Timing is dead on and getting correct advance. Compression is 150 across all cylinders

If all correct then you don't have an issue

 

[Excel23]

Compression is the only thing I have yet to check, new re man and the plugs are miserable to put in and out

 

[Excel23]

The intake i think is the biggest difference, instead of the stock 4 barrel it has a 2 sided multi plain

 

[saf]

You might want to check your ignition advancement. I had similar problem that I eventually traced to a faulty ignition module that stopped advancing. You should be seeing ~30 degrees @3000 rpm

 

[Excel23]

With or without a load? It is not a vacuum advance and my timing is at 10 degrees at 850 rpm

 

[Excel23]

And is that BTDC or ATDC?

 

[Excel23]

Well, here's a shock to me, freshed up my marks on the balancer and threw a timing light on it and I was set at 1 BTDC, adjusted it to 10 BTDC and reved it up to 2000 rpms and the timing advanced......... next weekend I will give her a go. It seems to be a nice crisp throttle response now.

 

[Excel23]

Well, timing was my issue, boat ran great until I heard a squealing and the rubber line from my PVC valve to carb had an unusual amount of smoke???? Think a bearing went. If my motor was re built and it came with a new oil pump, what would cause this????? Did I miss a break in or something? Everyone i have spoke with said if the cramk wasn't brand new there was no break in.

 

[alldodge]

While its best to take it easy for the first 20 hours, sounds like the motor was not rebuilt correctly

 

[Excel23]

I have been for right around 20 hours, carb problems and timing. Boat has been at various speeds and rpms 7-8 mpm up to 25 and from 800rpms up to 3000. Today was the first day after resetting timing and I was only at 4000 for 5 mins before it did what it did. I am hoping in can pull it and change the bearing. Would that need another break in?