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srbrd 454 bogs for second when open trottle quickly when loaded

S

slauder

Regular Contributor
I can climb up slowly to plane and cruse at 3100 rpm no problem (normal planning rpm), but if I gun thrttle from 1100 to get up quickly I get a bog near 2700 at times. It worrys me when it happens so I take load off by backing off the thrttles. I guess I look at carb's large bore side? I can change the filters again. Gas was getting old but new 150 gals fresh and still happened. MnBn
 
You might simply have a weak accelerator pump on the carb(s). You can see be pulling the arrestor off and working the throttle. A strong shot of gas shooting in each time indicates a good pump; a weak or intermittent squirt means a worn out pump, semi-blocked squirter, or other problems (that require a rebuild).

Finally--though you didn't mention what carb you have--many carbs have an adjustable linkage to change the amount of pump shot. If that's your case, place the linkage in the position that gives the most shot.

Jeff
 
Rochester quads. I've been trying to get them to cliff but never seem to get on his schedule. I think I should contact him now for a winter rebuild. I toy with edelbrock swap but most seem to think its not going to save gas which would be my reason for it.
 
If that engine bogs around 2700, I'd doubt the primary accelerator pump is the issue...

Have you checked the vacuum break to make sure it isn't damaged and is working correctly?

How about the tension spring on the air valve?

There are a few other potential issues, but those are most likely.
 
A few more suggestions:
check your base timing and total advance
remove and clean or replace the anti-siphon valve
 
Hi folks... Carbs are back from cliff and look and run great. No more lean running issue. Only thing is I had the event occur again. Happened twice. I have yet to change filters and will update you folks after. So we can run out the carbs I think since cliff was all over them and tested more then 20 minutes before shipped me back.


Any ideas on tracking down the issue? Single gas tank two engines. Always starboard. Is there a method to blow out the gas lines? I'm thinking must be something in the racor pineapples I am missing. I will take a good look at them when I change the 30 micron paper filters.
 
slauder said:
Hi folks... Carbs are back from cliff and look and run great. No more lean running issue. Only thing is I had the event occur again. Happened twice. I have yet to change filters and will update you folks after. So we can run out the carbs I think since cliff was all over them and tested more then 20 minutes before shipped me back.


Any ideas on tracking down the issue? Single gas tank two engines. Always starboard. Is there a method to blow out the gas lines? I'm thinking must be something in the racor pineapples I am missing. I will take a good look at them when I change the 30 micron paper filters.
Click to expand...

Ayuh,.... My guess is, ya pumped rotten dirty fuel through yer brand newly cleaned carb,...
 
Scott:

Carbs are likely to be just fine...but they need to have fuel in the bowl...so I'd suspect the quickest way would be to monitor the float level via the vent hole...you can use a straw and a sharpie...something light but easily visible...you can use the port for reference.

if the float levels stay consistently "up", then you need to make sure the ignition system is in good shape...especially the advance mechanism inside the distributor...erratic advance is a candidate for your symptoms....
 
Replaced filters and seemed better until I started getting some surging and then now we are not getting gas at all. Mark it's a real pain to drive the boat and monitor the carbs since I have to tilt the helm seat up with the hydrolic lift. Don't like moving on even small chop like that. Anyway I think it's clear now that bowl is dry and I'm not getting fuel.

the paper racor was very dirty and showed crap caught. I think my old flexible gas lines need to be replaced. I heard of breakdown on the old stuff they used back then (no history on them other then nothing by me for 7 years I own the 1991).

Does that hat sound like a probable cause? Assume a fuel pump works or doesn't but not interimtnt type issues.

i think the post 2008 lines are supposed to hold up to the ethonal I read. Newest evolution is A1-15. I think that's the stuff I need. Do you know if brands matter?
 
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the brand isn't critical, its that rating stamp that is....though I'd be inclined to get a decent brand name vs something nobody puts their name on...

If there is enough crud in the fuel pump, it can inhibit the valves from closing all the way and result in insufficient fuel delivery...
 
Did you replace that tiny filter in the carb body (behind the fuel connection)? That dopey thing has been responsible for lots of burnt pistons by plugging up.

If you have a decent filter located after the fuel pump (where it belongs) you can throw that thing out.

Jeff
 
Jeff,
cliff said he replaced it. I didn't look but I think i will pull it for inspection to be sure. Leaning out the engines is concerning
 
Anti syphon is at top of tank I think. How do I tell if I have one? What does it look like. I have not checked anything aft of the water separators. Will pull old Hoses tonight. I will look for it.
 
Inspected gas lines at two barbs... It looks good on inside. The line is A1 USCG MARINE 3/8. I don't think the line is the problem. I have anti syphon inline on top of tank under non removable deck. I can access it from the fishing box next to tank but very tight. I figured I would just test it. When I removed the line from barb at first filter, the racor 20 micron paper water separator, I found gas in line and when I sucked on it (not too hard) I got gas. I think we are good but wanted to know what pressure vacuum it should flow. I will measure with a tool later to be sure it's spec.

so I thinking next could be Oring issue on top of racor letting air in.... When I opened it I didn't think I had enough gas in it. I removed old Oring, cleaned racor lid and groove, installed new Oring. I filled the racor with gas and closed her up making sure to tighten it up well. I filled the carb bowl and started boat... Ran well for a while then ran out of gas.

I ran out of time and closed up for night. I think either I still have air leak or fuel pump. This is starboard engine so pump is tough to get to.

Thinking I could take the racor out of the picture by connecting the lines together to bypass. Also I could set my line after racor in a plastic tank bypassing anti syphon and racor.

I have steel lines from second filter, to the fuel pump and from the fuel pump to the carb.

I have a pressure/vacuum tester I used for cooling system and I think it can be used in fuel lines too. That should measure the pump I think.

is there a better way to debug this issue?
 
The inlet line of the fuel pump should show a slight steady vacuum with the engine running....maybe 1 - 2 " Hg....shouldn't be more than 4-5"...if it is, there is a restriction in the inlet plumbing....if the vacuum drops down towards 0", there's a leak in the inlet plumbing... its a bit of a pain but you can use the other engine (the one without the issue) as a reference...

if the suction side is good, it would be beneficial to measure the outlet pressure of the pump...its a bit of a pain with the standard steel line between the pump and the carb but it can be done...
 
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