Hi everyone. I am a new member to iBoats. I have received invaluable help from this forum in the past while building my project and have decided to join the community.
I recently restored a 1986 Glastron 19X ski boat (new deck, stringers, transom, etc.) and just finished rebuilding my engine (spun #1 rod bearing back in April). My engine is a Mercruiser 3.0L 140. The block’s serial number is 4943394 and Block Code M06037RA which would make it a 1977, model 140. The valve cover however, I believe is from the original ‘86 block as the serial number on it is A542548.
The issue I am having is with my engine. It bogs horribly on acceleration especially if I don’t go to WOT super fast. However, once I get past that bog she runs beautifully; very smooth and pulls under load no problem throughout the throttle. Second issue is when it idles, it’s not smooth. It shakes a lot especially when cold but will shake a fair amount too when hot. Strange thing is sometimes after warming up, it will idle smooth with no shaking but I’ll run it past idle and come back to idle and it’ll shake again and not smooth out.
My engine has the 1389-9350 MerCarb (which has the 3-3/4” x 2” bolt pattern base) that I believe was used on the 140s in the mid ‘80s. I also installed a brand new OEM stock mechanical fuel pump. I converted my stock Delco distributor from points and condenser to Pertronix 1146A Ignitor electronic ignition. The mechanical advance weights are operating and move freely. The cap, rotor, and plugs are 3 years old but are clean and plugs gapped to .035”. Also valves have all been adjusted per technical manual’s (number 10) instructions.
Here is what I have done. I’ve cleaned the carb twice using compressed air and carb cleaner through every port and galley clearing them of debris and installed a new kit w/ accelerator pump. I have set the air/fuel mixture screw with a vacuum gauge starting 1.25 turns out and tuned from there. The shaking at idle and air/fuel mixture screw response did improve a lot and the bog on acceleration improved only a little. My timing is set at 6 degrees at idle which is set to ~700 rpms in gear warm. I am thinking my carburetor is the source of my problems but would like to hear y’alls thoughts too. I have read where others solved their bog on acceleration my replacing their MerCarb’s main jets from 1.45mm to 1.65mm but haven’t attempted myself. From what I have read, the MerCarb is poorly designed with a faulty accelerator pump circuit that was never remedied.
I am leaning towards replacing this carb with a brand new casted carb, rather than a reman. Sierra offers a new casted replacement, 18-7370N, for my 1389-9350 which is around ~$400. Anyone experienced with it? National Carburetor also manufactures their own improved design replacement with better designed accelerator pump circuit and overall fuel delivery for $250 after core refund. However, it replaces 1389-9564 MerCarb (among others) which is an early ‘90s carb and after speaking to them on the phone, they said it’s a 50/50 chance it would work for my engine since mine is the “GM style MerCarb”. I do not think there’s that much difference between the 1389-9350 and the 1389-9564 but maybe so? National Carburetor did say they could rebuild my current carb for $200. Any other recommendations? I have been a customer of National Carb in the past and have been very pleased with their remans.
Bottom line, should I experiment more with my current carb, have it professionally rebuilt, or consider trying Sierra or National Carb’s replacement or something else? OR am I moving too fast and need to diagnose more extensively? I really appreciate y’all taking time to read this post and I will try to answer any additional needed details on my setup. I did the engine rebuild myself minus the machine work.
Pictures of my Engine and Carburetor can be found here: https://drive.google.com/open?id=1rcLp1fnnTBFcu4bLK3Rd7gi9m5INaoVE
Sierra Replacement:
https://www.marineengineparts.com/sierra-marine-18-7370n-carburetor
National Carb’s replacement from their eBay store and website:
https://www.ebay.com/itm/232836421042?ul_noapp=true
http://www.nationalcarburetors.com/marine/twobarrelmerc.aspx
Thanks in advance!
Doug
I recently restored a 1986 Glastron 19X ski boat (new deck, stringers, transom, etc.) and just finished rebuilding my engine (spun #1 rod bearing back in April). My engine is a Mercruiser 3.0L 140. The block’s serial number is 4943394 and Block Code M06037RA which would make it a 1977, model 140. The valve cover however, I believe is from the original ‘86 block as the serial number on it is A542548.
The issue I am having is with my engine. It bogs horribly on acceleration especially if I don’t go to WOT super fast. However, once I get past that bog she runs beautifully; very smooth and pulls under load no problem throughout the throttle. Second issue is when it idles, it’s not smooth. It shakes a lot especially when cold but will shake a fair amount too when hot. Strange thing is sometimes after warming up, it will idle smooth with no shaking but I’ll run it past idle and come back to idle and it’ll shake again and not smooth out.
My engine has the 1389-9350 MerCarb (which has the 3-3/4” x 2” bolt pattern base) that I believe was used on the 140s in the mid ‘80s. I also installed a brand new OEM stock mechanical fuel pump. I converted my stock Delco distributor from points and condenser to Pertronix 1146A Ignitor electronic ignition. The mechanical advance weights are operating and move freely. The cap, rotor, and plugs are 3 years old but are clean and plugs gapped to .035”. Also valves have all been adjusted per technical manual’s (number 10) instructions.
Here is what I have done. I’ve cleaned the carb twice using compressed air and carb cleaner through every port and galley clearing them of debris and installed a new kit w/ accelerator pump. I have set the air/fuel mixture screw with a vacuum gauge starting 1.25 turns out and tuned from there. The shaking at idle and air/fuel mixture screw response did improve a lot and the bog on acceleration improved only a little. My timing is set at 6 degrees at idle which is set to ~700 rpms in gear warm. I am thinking my carburetor is the source of my problems but would like to hear y’alls thoughts too. I have read where others solved their bog on acceleration my replacing their MerCarb’s main jets from 1.45mm to 1.65mm but haven’t attempted myself. From what I have read, the MerCarb is poorly designed with a faulty accelerator pump circuit that was never remedied.
I am leaning towards replacing this carb with a brand new casted carb, rather than a reman. Sierra offers a new casted replacement, 18-7370N, for my 1389-9350 which is around ~$400. Anyone experienced with it? National Carburetor also manufactures their own improved design replacement with better designed accelerator pump circuit and overall fuel delivery for $250 after core refund. However, it replaces 1389-9564 MerCarb (among others) which is an early ‘90s carb and after speaking to them on the phone, they said it’s a 50/50 chance it would work for my engine since mine is the “GM style MerCarb”. I do not think there’s that much difference between the 1389-9350 and the 1389-9564 but maybe so? National Carburetor did say they could rebuild my current carb for $200. Any other recommendations? I have been a customer of National Carb in the past and have been very pleased with their remans.
Bottom line, should I experiment more with my current carb, have it professionally rebuilt, or consider trying Sierra or National Carb’s replacement or something else? OR am I moving too fast and need to diagnose more extensively? I really appreciate y’all taking time to read this post and I will try to answer any additional needed details on my setup. I did the engine rebuild myself minus the machine work.
Pictures of my Engine and Carburetor can be found here: https://drive.google.com/open?id=1rcLp1fnnTBFcu4bLK3Rd7gi9m5INaoVE
Sierra Replacement:
https://www.marineengineparts.com/sierra-marine-18-7370n-carburetor
National Carb’s replacement from their eBay store and website:
https://www.ebay.com/itm/232836421042?ul_noapp=true
http://www.nationalcarburetors.com/marine/twobarrelmerc.aspx
Thanks in advance!
Doug
