Chevy 350 throttle question

[WaveRay]

We have a 28 Bertram with 350's. Recently we noticed that the port motor will only give about 3200 rpm. We normally get around 4k with it as we do with the strbd motor. This boat is new to us and I was hoping I can be educated a little here. What is the normal rpm range for these motors in this baot and what kind of speed should I see from them?
The motors have 250 hrs on them and are carburated. The linkage appears to be pulling equally on both motors. It just seems like we don't get full trottle on the port engine.
Anybody have any ideas where to look?

Thanks in advance, guys. This forum seems to have all the info I need.

Ray

[Bite Me]

If you were seeing 4K and now you're down to 3K you clearly have a problem. Have you checked your fuel filters? Depending on the carbs there are also some right at the carb intake.

If they're clean look towards ignition. Does it idle smoothly? You might have one bad cylinder, plug, wires, cap etc. At idle you can pull the plug wires one at a time AT THE CAP. Carefull here cause it's easy to get zapped. As you pull each wire one at a time you should see a reduction in rpm. If you pull a wire that does not slow the motor that is the weak cylinder. If you find the weak one, pull the plug. All of your plugs should have an amber color to the insulator. If you pull one that is black or wet, there is your problem. With only 250 hours I'd guess your problem is either filters or ignition and not a major mechanical issue.
What year are the motors? Are they Vortec? If they are new one would assume that they are. If Vortec ther will be 4 bolts holding down the intake manifold. If 6 then it is a non vortec motor.
What do you have for carbs? Some of the newer 350's are using Holley 600 CFM.
Stated HP on 350's goes from 260 to 330 depending on the year, carbs, manifolds etc.
Typically these motors should top out at around 44 t0 4650 RPM. You'll need to adjust props to that end then figure your cruise at about 80% of that.
There is lots that can be done to build torque in these things without breaking the bank.
In a 28 Bertram they should get the job done.

[WaveRay]

Thanks for the reply, B-M.
The motor runs great and has Hollys on it. I could not find any filters at the carb and we just replaced the fuel filters to try to correct this problem. I will try pulling wires although it does run smooth without any misses.
One other thing, after starting and idle-speed running past warm up, the first time we throttle the motors, this motor will spit two to four times then run the rest of the day fine. It is only on throttle up and, like I said , only the first time.
Again, thanks for the responses.

[budddavid]

Based on your mention of the spitting upon pouring the coals to it the first time, I would check the timing. Timing issues can be hidden once an engine is up to temperature but could affect reaching max rpm.

[Bite Me]

Based on your mention of the spitting upon pouring the coals to it the first time, I would check the timing. Timing issues can be hidden once an engine is up to temperature but could affect reaching max rpm.

Good point and while your at it check your advance mechanism as well.......

Depending on the carb look inside where the fuel line connects. Could be a gold looking pourous filter inside the carb body..........I think, it's been a long time.

Also possible that Cap or wires will run fine at idle and break down at RPM. Pull your plugs and look. I'll bet you find one that's fouled.

[GALAZIO]

Carbs work off vacuum. Check the opposite site of the carb from the linkage which controls the butterflies. There will be 4 or so fittings which have vacuum fittings/tubes or plugs (depending on your setup). Make sure these are all connected or sealed. If they are not, or leaking... performance will not be there. Simple check before jumping into any added expense.

[WaveRay]

Great replies! I'll be sure to check it all out. i'll let you know how it goes, Thanks!