Help! High Throttle hesitation

Well done, Kris!

So I am happy to report that it was a great trip to the lake this morning...   I was able to take 45 minutes on the ramp since I had the whole place to my self.   I checked ignition timing and found that it was accurate at 3000 RPM, ( 35°) and my 11° was good as an initial timing set point I think.   I also was able to work through the throttle/trans lever adjustment that I have been unhappy with.   Power was good with the replaced main breaker, so I launched the boat and spent about 2 hours of run time on the lake.    The throttle hesitation is definitely gone, and I varied the RPM from 1500 to ~4000 without spending too much time at any one RPM.    The carb rebuild was a good suggestion, and helped a lot Thanks to KENO and the others of you that chimed in.
    I liked the way the motor started better before the carb rebuild, now it takes a couple of throttle pumps at the ramp to get it to start cold, but I also noticed that the choke opens very quickly, so I may need to read up on delaying the opening a bit.   Over all, I am pretty happy.
I still have a little bit of a drive line vibration, but I suspect that is a prop issue.   I guess I will work through solving that as well, but it will likely take a back seat to the next few hours of boating time and getting the engine broken in.   

Timing is rpm driven, it can be verified while running on the driveway in about 2 minutes. It sounds like you should be I I good shape but verify for peace of mind with your brand new engine.

Kris, I am not a carb guy but your comment on Timing caught my attention.
You mentioned timing at idle. That is a good start but the important timing to measure is what you have at 2,500 rpm up to 4,000 rpm.   
Watch the timing mark move as you advance your rpm. It should advance smoothly as your rpm increases and max out around 35 degrees usually between 2,500 and 3,000 rpm.
The max or total timing number is the one that will give you performance or melt your engine.   If your distributor allows say 40 degrees at 3,000 rpm that is very dangerous for your pistons.   The only solution would be to recurve your distributor or back off the idle timing setting till your max is proper.
If your timing does not advance smoothly, if it jumps or does not move at all you need to go inside the distributor and repair it.
If your distributor as it is set now at 11 degrees is only at say 30 degrees at 3,000 you are leaving power on the table.   You can add idle timing to move your 3,000 rpm timing up or get the distributor re curved.   
Others that know the 351W better can give a better idea of the exact timing curve preferred but in general this is what you need to be aware of.
There are two ways to verify this. Any speed shop sells timing tape that you put on your harmonic balancer or you can measure exactly how far it is from 0 - 10 on your boat and add a new line at 20,25,30,35,
The easy way is to use a Set Back Timing light that allows you to dial in how much timing you want and use your normal timing marks. These are available for $80 or so and help.
I hope it purrs next time out.

Well? Any fun video to post?

Kevin

Dreaming wrote: One more fun fact for Ken The secondary plate seems to have a 59 stamped on it.   the five is pretty lightly stamped, but I think that was the correct number.

Not a lot I can tell you about that plate except that it's the stock plate for a fair number of marine 4160's and info on it is not very easy to find.

I have one on a 4160 that feeds a 351 with gt-40 heads with no problem at all.

Probably looked just like this

So I re-assembled the carb last night and just spent a couple of hours putting everything back together.    I reset the timing at 11°BTDC at 600 RPM.   then adjusted the carb idle needles for 16.5-17" vacuum (600 rpm).    I'll have to wait until tomorrow to throw the boat in the water, but it is running on the hose.    I hope all is well on the top end now, it does start good, and seems to idle nicely.   I did check the idle mixture screws, and they will make the engine die if I get them too far in, so we're running on the idle circuit at idle.    

One more fun fact for Ken The secondary plate seems to have a 59 stamped on it.   the five is pretty lightly stamped, but I think that was the correct number.   

Alright,   
There 3 sets of numbers on the horn of the carb, they are:

FIJL-CA
50469-1
3492

I believe the list # is the 3492, but not too sure at this point.    I may try and start assembling tonight, likely going to be tomorrow evening.

The whole 2.5 pv never made sense to me when they made that switch, especially to old list rebuild kits that used to come with a 5.5 or 6.5.

To have to wait til the vacuum is less than 2.5" before the carb switches from lean cruise to high load, only induces a distinct dull flat spot when you mash it.

When I talked to Holley's tech line a few years ago they told me they purged alot of the older carb info when they computerized

1980nautique wrote: Kris, cut and paste this address: "http://documents.holley.com/techlibrary_carb_numerical_listing.pd" into your browser. and use your LIST # and verify required Power Valve. Does the Carb have "J" tubes on the bowl vents?

Hey thanks for the chart   

I've got 7 marine 600 cfm 4160's either on boats or on the shelf   You might call me a hoarder or maybe somebody who likes spare parts

First one is a 6576 list number not on the Holley chart, it's old (from 1976) it's always had a 6.5 PV since it was new

Continuing on list number 50419-1 (have 2 of them) 2.5PV

List 9392 2.5 PV

List 7163 2.5 PV

List 80319-1   2.5 PV

and last but not least a list 75009 with a 6.5 PV

And all those PV numbers are from the Holley chart

Kris, cut and paste this address: "http://documents.holley.com/techlibrary_carb_numerical_listing.pd" into your browser. and use your LIST # and verify required Power Valve.
Does the Carb have "J" tubes on the bowl vents?

Tim - thanks for advice.   I did set timing etc, and will check it again once I reinstall the carb, and will also dial in the carb with a vacuum guage once it is re-set.   Cooling is working well, all systems were normal during my lake run on Monday.
I have followed the school of thought that rings need seating at all ranges of RPM, when new, so I'll adjust my speed expectations and run a little faster to make sure we set the rings correctly, but will not baby it so to speak.

1980 - sounds like good advice... no Idea where my vacuum numbers are right now, so I guess that you are suggesting I install the 2.5 that came in my kit and replace once I have accurate vacuum numbers?    

1980nautique wrote: I don't believe you will find a marine based Carb Kit for a 4160 Holley that comes with a 2.5 hg. Power valve the main difference in the Kit selection,besides the J Tubes, is the power valve selection. Keep us informed!!!!

I don't believe you're right

It's hard to find a later model 600 cfm marine Holley 4160 with something other than a 2.5 PV as the original PV.

Earlier ones a 6.5 was common

You should clean your !!!!! key too by the way

Kris,
I would use the proven method of Holley power Valve selection!!! The starting point is to check manifold vacuum at idle on a warmed up engine. Divide this number in half.
ex. 13 hg.'s at idle divided by 2= 6.5.
A 4.0 hg. power valve will slam shut at 4.1 hg.'s and begin to lean out the fuel mix as the engine recovers vacuum and RPMs at WOT.
Recommend putting in the 6.0 or 6.5 hg. Power valve that comes in the 4160 Holley marine Kit.
I don't believe you will find a marine based Carb Kit for a 4160 Holley that comes with a 2.5 hg. power valve
Compared to the street version the Power valve, Main Jet sizes and the J Tubes are the main difference in the Marine Carburetor,.Keep us informed!!!!