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M225D Bogs or dies under quick throttle
https://slantsix.org/forum/viewtopic.php?t=64876		 Page 1 of 2
Author:  ToddlyPDX [ Mon May 11, 2020 7:40 pm ]
Post subject:  M225D Bogs or dies under quick throttle
Hello to all, I’ve been enjoying learning from this forum for many things its been a great resource as i become familiar with my engine. I need a little help and am not finding exactly the info in any existing thread so this is my first post. Thanks to all in advance for any help or advice you can give.

What I have: M225D original to the 1968 SilverLine DeVille 17’ boat it is in. It has a Carter BBS (tag missing) with electric choke. A Chrysler type distributor (marine style with no vacuum advance).

Condition: mostly original with low hours as far as i can tell with basic wear items having been replaced. Runs. Starts easy cold or hot. Idles well at 850 - 900 RPMs. Accelerates smooth if done slowly. Cruises at 2000 RPMs all day with no issues.

What’s been replaced: Cap and rotor, points, condenser, plugs, wires and coil.

What’s been recently adjusted or checked: timing (with a light and by vacuum), idle mixture screw, choke

Problem: the engine dies/ bogs when throttled quickly from slow speed (1000 - 1200RPMs), bogs but sometimes takes off when throttled quickly from 1800 - 2000 RPM. It will go from 1000 RPM to full throttle smoothly with no issues if done so slow and smooth. The behavior is similar in neutral under no load but not as pronounced. Basically punching it kills it.

Any help or insight would be great or get out of here you boating fool is OK to, there just isn’t any slant 6 marine fanboy forums for me to join :P
Author:  slantzilla [ Mon May 11, 2020 8:38 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Is the accelerator pump working in the carb?
Author:  ToddlyPDX [ Mon May 11, 2020 8:47 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Slantzilla thanks for the response.

With apologies for my lack of knowledge I’m not sure how to test that. With the throttle linkage unhooked if i operate the accelerator pump by hand the amount of resistance and sounds i hear lead me to believe it works.
Author:  Dart270 [ Tue May 12, 2020 2:21 am ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Welcome to the site. Sounds like a cool boat!

If you look down the throttle bore while moving the throttle linkage with the engine off, you should see a strong stream of fuel shooting into the middle of the bore. If not, the pump diaphragm inside the carb may be worn out. With the engine running, you should see a stream that breaks up into a spray/mist in the throttle bore when you rev it.

See what that looks like and we can go from there...

Cheers,
Lou
Author:  SlantSixDan [ Tue May 12, 2020 10:44 am ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Yup, it does sound like your accelerator pump has failed and it's time to go through and rebuild the carburetor. Are you quite sure it's a BBS (1-barrel) and not a BBD (2-barrel)? As far as I'm aware (and according to the factory literature), all the marine 225s had the BBD 2-barrel. If you look again and find that to be the case, ordering a kit for a Carter BBD 3390 will get you the right kit. That would be a kit № 1283 from The Carburetor Shop in Missouri. Kits don't generally come with a proper float gauge any more, all you get is a useless strip-of-paper pretend ruler. That makes problems because setting the float height is a crucial part of rebuilding a carburetor (float wear is not likely, but the float must be checked to make sure gasoline hasn't got inside and made the float heavy). The Carburetor Shop sells gauges separately—the factory metal ones; don't know how much they charge. If too much, one workaround is to also buy an old-stock car/truck BBD kit off eBay, such as this one, and rob the float gauge out of it (pink cardboard item visible in one of the pics inside the bag).

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Also look at the tune-up parts and technique suggestions in this post (how long since this engine has had a valve adjustment?).
Author:  ToddlyPDX [ Tue May 12, 2020 12:58 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Thank everyone for your responses, very helpful.
I appreciate your patience with the novices, we all have to start somewhere....

I checked the function of the accelerator pump. No stream, so I the top off the carb and operate the pump by hand and fuel seems to squirt around the pump cup/ seal back into the bowl. I'll be looking for a rebuild kit.

I've put some pics of the boat, engine and carb so you guys can see what you are helping fix and to assit in more expert identification of the carb.
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Author:  Joshie225 [ Tue May 12, 2020 1:22 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Carter BBD. If the leather on the accelerator pump cup is in fair shape you can soak it in light oil so that it softens and swells enough to conform to the pump bore. Also, there needs to be a check ball in there so that fuel isn't pushed back out the pump inlet. This works like a squirt gun. There has to be a check valve between the reservoir and the pump so that the discharge goes to the nozzle.
Author:  Dart270 [ Tue May 12, 2020 6:06 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Yep, BBD. Hope the accel pump and rebuild works well. Pretty boat!!

Lou
Author:  ToddlyPDX [ Tue May 12, 2020 6:16 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Thanks everyone. I've read all the suggested material, downloaded the service manual for the BBD and I'm getting a rebuild kit.

I'll post when the job is done and share the results.
Author:  SlantSixDan [ Tue May 12, 2020 6:51 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Cool boat with a cool motor!

Also see here for another aspect of refurbishing the accelerator pump, that's not in the manual.
Author:  ToddlyPDX [ Sat May 16, 2020 11:10 am ]
Post subject:  Re: M225D Bogs or dies under quick throttle
OK Gang here’s the results. I rebuilt the carb and went for a test drive. The problem was resolved. You can now hit the throttle and it jumps right up and goes. If you do it fast enough to there is a slight pause but it doesn’t die.

I’d did discover the cause of the issue during disassembly. It was a stuck check ball in the venturi cluster not allowing the squirt from the accelerator pump to flow.

It runs smoother at idle and lower speeds as a result of the squeaky clean carb. BONUS!

Now the bad news. It did accentuate an issue i was not attributing to fuel flow. Prior to the carb rebuild during 70% - full throttle operation it would occasionally skip a beat but not die or really stumble significantly. It would quit for a split second then resume normal operation. It would happen once every 10 - 20 minutes and changing the RPMs a bit always stoped it. Now this is happening at at 50%+ throttle and more frequently.

Thank you all again for the help. I’ll seek info on the other issue on other threads so this can remain about the issue in the title.

Now back to work on that cool engine!

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File comment: Also here are the leftovers from the kit. If anyone wants them PM me and I’ll drop them in the mail.
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Author:  Joshie225 [ Sat May 16, 2020 3:40 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
If you have a breaker point distributor in that boat the first thing I would check is the condition of the points and probably replace the condenser.
Author:  matv91 [ Sat May 16, 2020 8:13 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
I do not know if this safe in a boat or not? After warmed up shut engine off pull top off carb. Measure fuel level to top of bowl. Record for future reference. Just my guess work but some times a custom float setting higher or lower cane make a difference. See the last picture in this thread. http://www.slantsix.org/forum/viewtopic ... 0&start=45
Author:  matv91 [ Sat May 16, 2020 8:44 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
Here is a very short film, about how an air bleed carb works. https://www.youtube.com/watch?v=aJMXh5F6ncE
Author:  matv91 [ Sat May 16, 2020 9:06 pm ]
Post subject:  Re: M225D Bogs or dies under quick throttle
About half way down this thread is picture with ruler. http://www.slantsix.org/forum/viewtopic ... 0&start=60
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