Cant get past 3000 RPM

[stoneez]

Hi,
I need a little help here, please. Here are the specs
79 Searay Sterndrive
23 ft Long
Brand New GM 350 Crate Motor
MSD Marine "drop in" ignition
New Plugs and wires.
Holly 650 4 barrel
High flow "Jeggs" air intake.

I just did a motor up grade to a GM crate motor to replace the aging 350. Up graded the ignition system and went with a sweet Holly performance carb. Now I have a problem. IT WILL NOT GO OVER 3000 RPM WHEN IN GEAR. If I disconnect throttle cable it will rev just fine, but when Im trying to use the throttle, no dice. I have adjusted the throttle cable and it is moving completely open. I will hit 3000 rpm at about half throttle but goes no farther when I continue to move it forward, and has no issue with power up through 3000. It acts like there is a rev limiter, but we did not install the rpm limiter in the new distributor cap. Any help would be deeply appreciated. I feel like we are missing something, but just cant figure out what.
Thanks
T

 

[QC]

May seem basic, but can you confirm you mean in gear, in the water. You mean 3000 RPM in gear driving the boat, right? Or in gear on the trailer?

 

[stoneez]

Sorry, yes, on the water in gear driving the boat.

 

[Bt Doctur]

sparkplug wire for #5 and #7 reversed?. firing order incorrect?

 

[stoneez]

Purr's like a kitten at idle, and runs strong up through 3000. It just stops at 3000 while driving. It's like there is a secondary governor somewhere, but figure out where.

 

[NHGuy]

I was just reading the MSD stuff the other day. Beautiful equipment, it will give you great service.
They do have rev limiters. To see where it is set watch the tach when you first turn on the key, some MSD rev limiters display where they are set by temporarily displaying the value. ie. turn on the key and see if the tach momentarily goes to 3k.
Whatever happens you ought to go to the MSD webpage and download the install sheet for your ignition and/or distributor. If you have a separate MSD box the revs can be limited by either the box or the distributor or both. Some use a module, and some just require following a setup procedure.
If you can't work it out find out the part #s and post them.

 

[NHGuy]

Wait a minute, did you say the throttle won't open past that point when it's in gear? Or that the motor won't rev even though the throttle is opening?

 

[stoneez]

It will not rev past 3000 with throttle wide open, while in gear.

 

[Eric 3.7LX Alpha 1]

If you disconnect the throttle cable it will rev just fine..... Someone was at the engine with the cable disconnected and in gear and worked the throttle on the carb and you got more than 3k by hand? With the cable connected to the carb you maxed at 3k?

 

[Fastatv]

Hi,
I need a little help here, please. Here are the specs
79 Searay Sterndrive
23 ft Long
Brand New GM 350 Crate Motor
MSD Marine "drop in" ignition
New Plugs and wires.
Holly 650 4 barrel
High flow "Jeggs" air intake.

I just did a motor up grade to a GM crate motor to replace the aging 350. Up graded the ignition system and went with a sweet Holly performance carb. Now I have a problem. IT WILL NOT GO OVER 3000 RPM WHEN IN GEAR. If I disconnect throttle cable it will rev just fine, but when Im trying to use the throttle, no dice. I have adjusted the throttle cable and it is moving completely open. I will hit 3000 rpm at about half throttle but goes no farther when I continue to move it forward, and has no issue with power up through 3000. It acts like there is a rev limiter, but we did not install the rpm limiter in the new distributor cap. Any help would be deeply appreciated. I feel like we are missing something, but just cant figure out what.
Thanks
T

Possibly too much carb? While underway, and under load of course, can you look and see if the carb secondarys are actually opening up at all? Or possibly too large of a pitched prop?

 

[stoneez]

So, here is where we are with this........ On friday, I will be putting the original intake back on and see if that makes a difference. We are concerned that the intake may be the issue. The secondary's are not opening even with the lightest spring for the spring kit to replace the stock. So Sat it will be back at the lake with old intake and we will give it a run again. Seems like the problem only exists when under load in the water.
As for the prop, it is the same I had with the old motor, and the 40 yrs old motor ran it just fine. We think that the intake may be to big to create enough vacuum and it may not line up properly.
Will Update when I have more info. Thanks guys.

 

[Fastatv]

If the intake doesn't resolve the issue, if you still have it, you might try the original carb. I'm assuming it was a Rochester Quadrajet. At least you have eliminated the prop as the possible issue. Good luck and let us know how it turns out. Rick

 

[Bt Doctur]

~~concerned that the intake may be the issue. The secondary's are not opening even with the lightest spring for the spring kit to replace the stock

Holly 650 dosent use a vac secondary??????????????? What carb is on it???????????

 

[Southtowns27]

If it's a dual plane intake, don't waste your time swapping it out, that's not the issue. Something is jacked up with the carb. Can you post a couple pictures of the carb/linkage setup you have?
What's the horsepower rating of the new engine?

Edit: And just had another thought... What does the carb have for a choke setup? If the choke isn't pulling off all the way, it will block the secondaries from opening...

 

[stoneez]

Bt Doctur, it is a 650 with vacuum secondary.

Southtowns27, the one on there now is the 3rd 4 barrel we have tried. We had a 750, then pulled the carb off my buddy's race care that runs a 350 ci, and now the 650. The motor is rated at 260 hp. As for the choke, we dont have it hooked up, but will look at it and make sure it's not causing any issues.

The intake on currently is dual plane, not sure what the old one is. When it comes to mechanical, I am lacking but learning quickly.

 

[MikDee]

As Southtowns 27 mentioned, There might be a mechanical linkage choke lockout to keep the secondarys from opening until the engine is fully warmed up, and the choke butter fly is fully open, on the far side of the carb. If so, then the choke butterfly must be setup to stay fully open at all times (if you're not using the choke).

I'm with Bt Doctur on this one, it sounds like a couple of crossed spark plug wires? Check that 1st!