Engines bog/stall, persistant issue

[LilRedNeckGirl]

1985 wellcraft, GM 3.0 inline 4cyl. Issue affects BOTH engines.
Serviced @ rebuilt carbs, checked chokes, new dist cap, points, wires, rotor, plugs. Water seperators and small inline filters, fresh gas, ...
Start engines from dead cold, easy start. Idle fine. Temp reaches 160. [operating temp] shifts fine, throttle up normaly, engines [both] bog then stall. forget hole shots, thats a sure stall. they can be coaxed up and after 2000 rpm, they are fine, hammer down and here we go. other then the mentioned issue, engines run fine, good compression, no knocks or taps, no smoke, no vibration.
idle speed is steady 600 on both. both are affected between idle and 2000 rpm. carbs are clean and seemingly not the issue. fuel consumption, @ 30/35 gal apx on a weekend that see's apx 100 miles of travel with both engines running.
I was thinking the vacume /spark/timeing advance but these carbs dont have vac hookups.. Its got me stumped. water sports are on the menu this summer with the grand children moving back into my life. Gotta find/figure out the "Gremlin" and get this boat doing hole shots...

 

[LilRedNeckGirl]

Re: Engines bog/stall, persistant issue

Additional info. Bought the boat a year ago, its had this issue from the start. One engine needed a head gasket, the head was then rebuilt, new gaskets, everything by the book. this is the start of season 2 on this boat and this issue is getting really old. a few mechanics have looked at it but to no avail. We run seafoam in the gas at about 50% of the recomended mix. we use a good ethanol free gas. [most of the time] . Tank is aluminum, cleaned last year so no dirt or water issues, 100 gal capacity . Fuel pumps are new last year. All fuel lines are new last year. Seperator filters are the new canister screw on type that resemble oil filters.
If the outdrives are in neutral, the issue doesnt manafest. both engines will rev up fine with no load on the engine. its only when the outdrive is placed in gear that the issue arises..

 

[Bondo]

Re: Engines bog/stall, persistant issue

Serviced @ rebuilt carbs,

Ayuh,... It sounds like a Carb Issue,...Accelerator pumps maybe....

And,... Rebuilding an old carb is a 50/50 shot, at Best, even in a fully equiped shop, 'n knowledgable Mechanic....

 

[Augoose]

Re: Engines bog/stall, persistant issue

Powervalve failure or accelerator pump adjustment? If you can slowly increase speed with no issue but then stumble out of the hole when hitting it, I'd say you are not getting the extra surge of fuel you need from the powervalve.

Its been awhile, but Bondo, doesn't the powervalve provide the initial shot and then the accelerator pump provides a smaller and "adjustable timed" shot afterwards?