1974 grew 240 electric shift bogs at WOT

[biffripjock]

hello everyone
i have a grew 240 cuddy cabin wiht a 8 cyl chevy 350 and electirc shift stern drive. last year i replaced hte lower unit as my forward coil spring broke. all of last year we had great boating on the west coast of vancouver island. this year i have had 3 sea trials and cant get it to run right. in the driveway it idles, starts, can stay at 2k rpm or 3k rpm, ( only 15 seconds or so by working the throttle). i know not to run at high revs with no load for long periods. basically i can run up and down in rpms no problem purrs like a kitten. but in the water, she idles, can make maybe 1500 rpm but as soon as i apply throttle it bogs. I have a new carburetor last year, new mechanical fuel pump, have cut a hole in my fuel tank and cleaned all the ick out of it ( last year problem, what trouble shooting nightmare that was) it really seems carburator related or fuel related. clean gas in tank, carb is clean. does anyone have any advice
i am considering throwing in another new pump
thank you

 

[southkogs]

Welcome aboard.

Have you checked compression? I'm not sure how to check fuel flow without looking that up, but before I did anything with the pump I'd confirm if it's not pumping right.

 

[biffripjock]

hi
thanks for the reply
its definitely a load issue, not sure if your talking compression in the motor? i have also read that the lobes on the cam can become grooved or worn so making a fuel starve issue appear under heavy load, not able to pump the diaphragm of the pump fast enough. i was wondering about other things to look for maybe in the leg itself or if anyone has experianced similar issue, damn hard to trouble shoot as when in the driveway it runs like a top

 

[southkogs]

74 should be electric shift, so the few things that happen in there don't fit (IMHO) the symptoms. If your lower were screwed up, you wouldn't "bog." The upper might get gummy, but I would think it'd be a different feel - it's more likely to lock up from water intrusion (which you can check your upper lube for water - maybe it's all rusty and nasty in there).

The drive shafts do wear out in the drives, but that would cause you to wind out more than bog.

I'm wondering if your cylinder compression is good on the engine. If you've got a bad head gasket or something that can cause you to bog out, and in a '74 it wouldn't be out of place for that to give out. I think you could answer the cam question by measuring your fuel flow.

 

[biffripjock]

re - replaced the fuel pump, no change
took carb apart (edelbrock 600cfm) found one float totally mis set and the float chambers full of black dusty substance in the bottom of the bowls. a mechanic friend of mine said he seen that before the rubber hosing breaking down over time and emulsifying. i cleaned it all out sea trial this weekend hope that's the problem. of course replaced all fuel lines with CG approved hoses