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230 HP OMC Carburetor

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    Posted: June-23-2017 at 1:39pm
Hello,
I purchased a 1978 Mustang last fall that's in very nice condition. The seller admitted to not being mechanically inclined. My question relates to the carburetor. The engine is the 305ci OMC 230 HP. Presently there is a Holly 7445-4 650 CFM installed. There's also a new Mallory distributor. One other observation is that the Morse throttle - clutch single lever control looks to be upside down. The neutral pull lever is in front of the throttle advance not to the rear. This is an odd set up as you have to pull the lever and then move the throttle in reverse for a neutral fast idle. Obviously not an issue but may contribute to the poor engine behavior.
Symptoms::: The engine starts easily when cold but requires throttle advance when warm.
                        Engine operates at the proper temperature zone, 160.
                        Planes very easily around 1,700 RPM and does 20 MPH at around 2,200 RPM
                                    I haven't verified the RPM with my timing light just yet.
                        When the engine reaches around 3,200 RPM it pretty much is at it's limit. advancing the throttle doesn't increase the RPM.
                        If running the boat at 3,000 or so RPM and then cut back the throttle quickly the engine will stall, sometimes with a cough, or semi backfire, It will start right up but only if the throttle is advanced.

So is the carburetor that's installed the proper one from the factory?
Does anyone think that this engine is over carbureted? (Too much fuel at higher throttle advance not allowing the engine to efficiently burn all the fuel?)
Timing, plugs, spark, are all good, even compression, idles perfectly, new fuel filter.
I do think the Morse control may be the culprit, I have to have someone go with me who will hand operate the carburetor throttle without the cable attached to see if that makes a difference.
Any ideas or suggestions would be appreciated. Thank you,

Tony D
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-23-2017 at 5:09pm
Tony,
Welcome to CCfan. We'd love to see some pictures.

Regarding the MV1, there really isn't any right side up. They can be mounted in any position. With the neutral safety pin pulled it's common for the handle to only go into the reverse position.

Regarding the 3200 max RPM, do check it with the shop tach but also, what prop (dia. and pitch) are you running.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-23-2017 at 5:22pm
I did wonder if it was over propped. I have to check, Not sure how to post pictures but I will..
Put a new fuel pump on as I wasn't thrilled running a 40 year old pump. The previous owner installed a different set up for the water pump that works quite well.. It looks like the 230 HP OMC wasn't a popular option.   I appreciate the advise on the Morse control, I've had them in many boats but never with the neutral pull forward of the throttle. Outboard engine controls are usually limited in reverse throttle movement. I wasn't sure about the inboard. I had a 1961 Chris Craft Super Sport 21 with a 283 and Morse single lever control. but I couldn't recall if the reverse was limited. Visually I checked the carburetor butterfly and it was full open at WOT. Sounds like I may be down to the prop unless someone can verify if the 650 CFM is too large.

Thanks for the help.
Tony D
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 75 Tique Quote  Post ReplyReply Direct Link To This Post Posted: June-23-2017 at 6:07pm
Not a big motor head, so not going to be a big help. I am just commenting because I have the same engine. Yes, the chevy/OMC does seem to be a bit rare, on my 76 I believe it was a $200 option. The chevies seem to have just a little more higher end than the stock 302s. The standard Holley 4160 that most 351s have is a 600 CFM I believe. I have on my 305,(what is believe is a replaced by PO) an Edelbrock that is a 600 CFM. There are carb to CID calculators on the interwebs, here is a clip of an example.



My 305 runs about 5000. You can see from the clip what the CFM calcs are. I think my boat runs pretty well, I dont know the "side effects" of running a carb with a greater CFM capacity than the engine requires. I am not sure what engine volumetric efficiency is, but since 83 was the default, I went with that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-23-2017 at 6:51pm
Tony,
Did you happen to check if the secondary's are opening?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 1:56am
My 260 Omc is a 350 ci. Mine has the original Quadrajet 4MV carb. Carb number is 7040284. I'll see if I can find your carb number through a search.
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 2:31am
Found number 7028280. This would be a Rochester number stamped on the port side of the carb. "75 Tique" would have the same carb. I bet he could check it for you.
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 8:43am
Your model will also allow me to look it up more accurately( ie 990324M).
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 1:04pm
Hi and thanks for all the help.
The secondaries are vacuum controlled so I'd have to have the engine cover opened the flame arrester off and someone running the boat. As far as moving them by hand all the linkage works easily.
So the quick answer is I'm not sure other than it sounds like they are opening.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 1:22pm
As far as the carb number goes, in my particular case my boat is equipped with a Holly
7445-4. 650 CFM 4bbl. The 350ci - 260 hp is a newer engine and it depends on the Company who marineized the engine. Mine being an OMC. I guess the question is does anyone have the mid 70's OMC 305-230 HP. I have a feeling the original may have been a Rochester.   If so I'll have to re-jet or find the proper carburetor.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 3:38pm
In 1978 CC would have put that in their boats. Omc would be the marinizer. Post some pics of the engine and model number.
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 4:53pm
Here's what I get from this thread.

Tony has a 78 OMC with a 650 Holley. It's almost a sure thing that it's not the original carb.

Steve has a 76 OMC with the original carb, his serial numbers on the carb verify that.

Steve's trying to help you out by telling you what most likely came on your engine originally and that would be a Quadrajet with the serial number 7028280.

I agree with Steve on that information. It would have originally had a Quadrajet.

You seem to want to blame the lack of revs on the carburetor. On either the Holley or a Quadrajet you have vacuum operated secondaries (the q-jet is mechanical secondary butterfly with a vacuum operated air valve) that although they function differently from each other will only open far enough to let the amount of air through that the engine demands.

So your Holley secondaries will partially open at full throttle but your engine can,t pull enough air through it for the secondaries to ever want to fully open.

The carb can flow 650 cfm but it won't because the engine can't use that much air.

Too big a carburetor isn't gonna have the effect you're seeing but a badly adjusted, dirty carb needing a rebuild might.

You mention timing being right . What is the timing set at while idling and what's the timing at 3000 rpm? It should be around 6 to 10 at idle and at 3000 at least 30 preferably
34-36

What size prop do you have?

How fast are you going at 3000 rpm?

Do you know the tach is accurate?

Will the throttle lever open the primaries fully? You can check this with the engine off. If it does then you don't have Morse control problems

Lots of questions, but the answers will help you figure out your issue or issues
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 5:10pm
Here's a list of OMC engines and carbs
Click on the OMC section

I don't think you'll find an OMC Small block Chevy v-8 with a Holley as original equipment but you'll find the number Steve gave you 7028280 listed for your engine size
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 10:51pm
990322A is the engine model.
The rest of the questions will require some investigation.
I do know the primary butterfly opens fully when the throttle is advanced to WOT.
I Have to pull the prop in order to identify its size and pitch.
As far as how fast at 3,000 I'll measure that with my phone.
My timing light has a Tach so I'll check the RMP accuracy.
I can also see how the timing lines up with your calculations.
Thank you for all this helpful information.
I honestly don't know how to post pictures on the forum.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 10:55pm
Your list number doesn't show up in any Holley charts that I have but since you know it's a 650, you must have some info on it.

It may be a 4165/4175 spread bore Quadrajet replacement carburetor and if that's the case,it's quite a bit different than the 4160 type Holley and it also may or may not be a marine carburetor.

Pictures would be a big help
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: June-24-2017 at 11:28pm
Nothing to add other than a hearty recommendation to follow KENO's advice... he shall lead you home.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 1:26am
From your first post,you mention rpm's up to 3200 and that's it. I think I would also check your advance springs in the distributor. Could be an issue there. We love springs, don't we Ken? I believe my service manual covers your model number. I'll let you know.
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 1:49am
. Correction, there should be a "B" after the carb number. I don't know what that means or if it makes any difference. M The service manual I have covers your motor.
1976 Martinique,350 Omc. 1975 Glastron/Carlson CV16,115 Merc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 6:26am
Originally posted by adaily adaily wrote:


I honestly don't know how to post pictures on the forum.

Anthony,
Use the "post reply" rather than the quick you find at the bottom of each thread. Click on the icon of the tree with the up arrow. A browse box will come up allowing you to select anything off your computer.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 9:10am
Originally posted by swilliams swilliams wrote:

From your first post,you mention rpm's up to 3200 and that's it. I think I would also check your advance springs in the distributor. Could be an issue there. We love springs, don't we Ken? I believe my service manual covers your model number. I'll let you know.


Yes we do , actually just distributors in general
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 9:14am
Originally posted by TRBenj TRBenj wrote:

Nothing to add other than a hearty recommendation to follow KENO's advice... he shall lead you home.


Make that WE shall lead you home, we being CCF.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 10:39am



A few pictures of the ailing Carburetor.

Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 11:33am
Thanks for the pics Tony. Issues with that carb might be far reaching. The correct carb might be in your best interest. Also, is that a prestolite or Mallory distributor? You might want to inspect the guts on that also. a service and parts manual is great to have. On the service manual, look for an original OMC SDL-1092. Parts manual 981296 will cover 990322M but not 990322A. You might have to research a little more for the correct one but I bet their close enough. Steve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote swilliams Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 11:44am
Parts manual 980922 is the one you want. Found some on ebay. The Ken Cook manuals seem to be a bit pricy but others are available.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 11:44am
Interesting,that last picture is not of the carb list number. It is located on the air horn where the choke plate is. That's is why Ken could not find a listing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 11:50am
The distributor is a new Mallory. Came with the boat. It's still set up with points although I do have an electronic module in the box.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 12:03pm
Originally posted by adaily adaily wrote:

It's still set up with points although I do have an electronic module in the box.


Why are you going to the EI conversion?


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This shows the choke side of the carburetor. The number is 603A

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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 12:09pm
The module came with the boat, I haven't decided to install it. That's the least of my issues right now. I do see the recommended carburetors for sale. That seems to be something I should consider. I'm not comfortable with having the wrong size and make on this engine. Most of my experience has been with outboards.

Tony
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adaily Quote  Post ReplyReply Direct Link To This Post Posted: June-25-2017 at 12:31pm
e Bay item, 371316091891 Should this be the correct carb? Rather than fooling around would anyone suggest just installing it.?

Tony
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