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tiupc
07-18-2013, 09:26 AM
I have a 75 Ski Sporter with a 2011 crate 350 in it. Runs great at WOT ( 4800 rpm) and at idle. When slowing down below about 3800 rpm, the motor seems to have a miss in it. Opening the throttle, it will speed up to 4800 rpm again and seem to run fine. Motor sounds like it is missing from about 2600 - 3800 rpm. I changed from Corsa Thru hull to Straight thru hull exhaust. This was when I noticed the miss in the engine. I have changed the plugs, wires, Distributor cap, rotor and the fuel filter. Motor has less than 30 hours on it.

Any suggestions

Thanks
Trevor

Tidbart
07-18-2013, 11:41 AM
Could be a carb issue. Is this carbed? If so, what type?

tiupc
07-18-2013, 12:18 PM
Holley 4 barrel I think a 4160. I will check tonight as the boat is at the cottage. I should also be able to tell if manual or vacuum secondaries ( there is a vacuum outlet on back of carb, choke side but it is blocked off. Also, choke is not powered, never has been.

Thanks
Trevor

biggiefl
07-18-2013, 02:15 PM
A 4160 is Holley's vac carb...600cfm but they also have a 750 under the same #. Something is weird obviously. Why did you disconnect the exhaust? Was it running fine before? If so you probably knocked off a vac line or ironically something went awry. I had a 4160 on my old Nova and was constantly having problems with it. Vowed never to own one again but it was just that particular carb that had major float problems.

MOP
07-18-2013, 02:49 PM
By getting rid of the Corsa which are mufflers you may have a back pressure issue, you may need to do some jetting as you can be running lean now. Best advice on this issue will come from Buzilla. It would be a good idea to pull a few spark plugs, post a couple pf shots up here for us to take a look at.

Phil

tiupc
07-18-2013, 07:29 PM
I looked at the carb horn and the only numbers are 6057-5 and underneath 3186. The secondaries are mechanical but when I open the throttle on the carb, the secondaries do not open. The linkage does not pull far enough. the motor runs up to 4800 - 5000 with a 280 drive Solas 21 pitch Titan. The carb does have a vacuum fitting on the choke side but this was blocked from when I got the boat and there are no lines or hoses any where else on the carb. I did notice a small tube coming off the mech fuel pump but I don't see any where for this to join to It is about 2 ft long. The Corsa's don't appear to be mufflers as the sound is the same . I changed to straight tip to match original more closely. I will pull some plugs and post pictures. I also will put the Corsa's back on to see if this makes a difference. If anyone can tell me about the Holley Carb as I can't find info on it. I have a feeling this isn't a marine carb. Any info/help is greatly appreciated

Trevor

joseph m. hahnl
07-18-2013, 08:00 PM
I looked at the carb horn and the only numbers are 6057-5 and underneath 3186. The secondaries are mechanical but when I open the throttle on the carb, the secondaries do not open. The linkage does not pull far enough. the motor runs up to 4800 - 5000 with a 280 drive Solas 21 pitch Titan. The carb does have a vacuum fitting on the choke side but this was blocked from when I got the boat and there are no lines or hoses any where else on the carb. I did notice a small tube coming off the mech fuel pump but I don't see any where for this to join to It is about 2 ft long. The Corsa's don't appear to be mufflers as the sound is the same . I changed to straight tip to match original more closely. I will pull some plugs and post pictures. I also will put the Corsa's back on to see if this makes a difference. If anyone can tell me about the Holley Carb as I can't find info on it. I have a feeling this isn't a marine carb. Any info/help is greatly appreciated

Trevor The tube goes on the blocked of fitting on the carb. That is a Fire in the bilge :kaioken: Bro!. That's an over flow for the fuel pump should it rupture the Diaphragm.

BUIZILLA
07-18-2013, 08:11 PM
I don't see a 6057-5 listed here >>

http://www.holley.com/data/TechService/Technical/Carb%20Numerical%20Listing.pdf

tiupc
07-18-2013, 08:45 PM
Joseph, thank you for the info re the tube from the fuel pump. It is not long enough to go to the carb. I will get a longer tube: should I connect it to the vacuum fitting on the back of the carb ?(back of the carb refers to position towards back of boat). Any insight as to why the secondaries don't open using the throttle ?
I couldn't find this carb in a Holley listing either. Can you tell if it is a marine carb by pictures. I will also post a picture of the carb.

Thanks
Trevor

MOP
07-18-2013, 09:36 PM
The tube coming from the fuel pump goes to the air breather not to any other place, if the fuel pumps diaphragm ruptures the fuel will dump into the carb. It is special and must be of the CG approved type, it also is designed to collapse in case of fire.

A marine carb is easy to ID the bowl vent tubes are U shaped, if the carb floods the fuel dumps down into the carb.

joseph m. hahnl
07-18-2013, 10:13 PM
The tube coming from the fuel pump goes to the air breather not to any other place, if the fuel pumps diaphragm ruptures the fuel will dump into the carb. It is special and must be of the CG approved type, it also is designed to collapse in case of fire.

A marine carb is easy to ID the bowl vent tubes are U shaped, if the carb floods the fuel dumps down into the carb. Both of my marine Webber and Edelbrock have a fitting at the top of the venturi .I assumed that a Holly had the same thing.:cool!:

Dakari
07-19-2013, 05:52 AM
Im having the same exact problem with my Holley 650 on my X-18...same rpm range. And its definitely not electrical...changed out all that you have PLUS the ignition box (had one lying around). We're thinking we may have some piece of junk in one of the secondary jets...

MOP
07-19-2013, 08:41 AM
Both of my marine Webber and Edelbrock have a fitting at the top of the venturi .I assumed that a Holly had the same thing.:cool!:

Joe we are on the same page, the point I was making is it should never be routed to the manifold or carb adapter. The engineers at tech school made a point of not having it subject to full engine vacuum, like you said many are on an air horn fitting. On my Holley it goes to a fitting on the breather similar to what is pictured below.

BUIZILLA
07-19-2013, 09:53 AM
a 4160 series is a square bore base and will have a fuel transfer tube between the bowls on the left side and is NOT normally mechanical secondary

a 4150 series is also a square bore base and will NOT have the transfer tube, and can be either mech or vacuum secondaries

it's best you post a pic of the carb before going further, since your not sure what model it is, and the model you say it is doesn't appear on the available literature (I have seen carb numbers in the field that are not on that literature however)

the rpm range your having the issue may also be the peak torque hump the engine is seeing, and it needs more fuel to get over that hump, or steadily maintain it, not an unusual condition to solve

with all that digested, IMO you have a lean cruise condition due to the primary jets being too small, or the power valve opening point being lower than needed and it's not opening soon enough. The mufflers / straight exhaust have zero to do with it. If you look at the literature. very few, if any, of the 600's have primary jets larger than 62's,,, a couple are even in the high 50's.... a 350 engine needs a minimum of a 68, if not 70-72 in the primary side, and a minimum 1 9/16 to 1 5/8 throttle blade, with a minimum 6.5 power valve in the front metering block. You have to start there. I have never been a fan of vacuum sec. carbs on a boat since the engine loading is vastly different than what a car see's in normal operation.

max tuning a 4160 series with rear metering blocks is an expensive and time consuming PITA

just my .03, and i'm SURE somebody will disagree :biggrin:

Donziman101
07-19-2013, 10:28 AM
my father has a holley 4160 on his 66 16 the carb has always been tempermental try a can of seaform always had a lean condition after sitting when warm seemed as though we had this problem when we went back to go water skiing after sitting when hot anyone let me know what a good marine carb.

Just Say N20
07-19-2013, 10:41 AM
max tuning a 4160 series with rear metering blocks is an expensive and time consuming PITA

just my .03, and i'm SURE somebody will disagree :biggrin:

Having gone through that whole process, I AGREE!

tiupc
07-19-2013, 12:26 PM
76689766907669376694766957669276691

Plug on left is #6 and right is #4 4th pic shows number of 8050B

Since this is an automotive carb, would I be better to purchase a marine carb probably a 0-80551 Holley or Mallory Any other suggestions ? Thanks to all who have taken the time to answer.

Trevor
Canada

BUIZILLA
07-19-2013, 01:22 PM
here's my take on the pic's >

get rid of that spacer :rolleyes:

by looking at the plug strap color the timing is pretty close, might stand to be advanced another 2*...

good upper ceramic color ring on the lower plug, lean on the upper plug, gaps look different, I can't see the lower internal ceramic color, but what I do see is very typical of a badly jetted dual plane intake, with maybe partially plugged main housing air bleeds

the 80457-5 isn't on my chart... but I would throw in a pair of 69 front jets and a new 6.5 PV in the front side, kill the spacer, and get a 1/4" bakelite spacer instead, advance the timing 2*, no more than 32* total and see what happens for giggles

if the timing is already there, then you have crappy slow burn fuel because I see some residue on the strap that shouldn't be there

tiupc
07-19-2013, 02:15 PM
Thank you Jim for looking at the pictures. My concern now is that this is an Automotive carb. There is no place to connect the overflow tube from the fuel pump. I believe this is a fire hazard. Would a Holley 0-80551 (4160 or Mallory equivalent work.

Thanks

Trevor

Stevo440
07-19-2013, 02:52 PM
Trevor

Well the carb is a vacuum secondary carb not mechanical. You can see the vacuum actuator in the picture of the carb from the opposite side of the throttle linkage (picture #6). The secondaries will never open when you open the throttle all the way without the engine running, it only opens with vacuum.
There is a small vacuum port coming out of the metering block (picture #6 also) that is open, that needs to be plugged or connected to the distributor, but being this is a boat engine and there is usually no vacuum advance in the distributor, you should plug it.
On the secondary actuator it says Performance Carb. these carbs are usually jetted richer then standard automotive 4150/4160 carbs.
One more point, make sure the choke plate is under spring tension to stay open all the time if you are not using it, by rotating the black choke housing.

Just adding to what has already been stated.

Good luck
Steve
ps Presently also in Canada (Montreal area working)

Tidbart
07-19-2013, 06:00 PM
Info on id'ing the type of carb

http://www.cpperformance.com/t-carburetor_selection.aspx?skinid=5

joseph m. hahnl
07-19-2013, 09:44 PM
Thank you Jim for looking at the pictures. My concern now is that this is an Automotive carb. There is no place to connect the overflow tube from the fuel pump. I believe this is a fire hazard. Would a Holley 0-80551 (4160 or Mallory equivalent work.

Thanks

Trevor

76698 (http://www.edelbrock.com/automotive_new/mc/carbs_acc/marine.shtml)

joseph m. hahnl
07-20-2013, 08:50 AM
here's my take on the pic's >

get rid of that spacer :rolleyes:

by looking at the plug strap color the timing is pretty close, might stand to be advanced another 2*...

good upper ceramic color ring on the lower plug, lean on the upper plug, gaps look different, I can't see the lower internal ceramic color, but what I do see is very typical of a badly jetted dual plane intake, with maybe partially plugged main housing air bleeds

the 80457-5 isn't on my chart... but I would throw in a pair of 69 front jets and a new 6.5 PV in the front side, kill the spacer, and get a 1/4" bakelite spacer instead, advance the timing 2*, no more than 32* total and see what happens for giggles

if the timing is already there, then you have crappy slow burn fuel because I see some residue on the strap that shouldn't be there I tried my 400, with and with out a thermal spacer. I used a single plane 1" spacer .I lost 250RPM right off the top by taking it off. It did have slightly better throttle response :drive: at lower RPM with out it. But 250 RPM loss is huge. I think your onto something with the power valve. A vacuum gauge is always handy when setting up a Holley:D

BUIZILLA
07-20-2013, 09:29 AM
I tried my 400, with and with out a thermal spacer. I used a single plane 1" spacer .I lost 250RPM right off the top by taking it off. It did have slightly better throttle response :drive: at lower RPM with out it. But 250 RPM loss is huge. I think your onto something with the power valve. A vacuum gauge is always handy when setting up a Holley:D problem is, he has a dual plane intake... and a thermal spacer doesn't have the ribbed internals, and isn't metal either... :wink: a spacer is used to tune runner length characteristics and can be VERY beneficial up top, mid range not so much.. as was pointed out before, that open vacuum nipple and too small jets could be the only issue.. good catch on the open vacuum nipple, as that is a ported nipple and really only see's a vacuum reference once the throttle is opened..

MOP
07-20-2013, 02:34 PM
Since he has an automotive carb his best move would be to find a marine 650, 750 on a 350 is a bit much. I run a 750 on my 383, I think it would run nicer with a 650. A 650 may take a tiny bit off my top end but who cares!!!!

Pat McPherson
07-24-2013, 11:09 PM
76698 (http://www.edelbrock.com/automotive_new/mc/carbs_acc/marine.shtml)

For under $300 you can buy a 600CFM Edelbrock with an electric choke bolt it on and go boating...