1978 sea ray sundancer 240 engine boggs out at 3/4 to full throttle

[hucksterfool]

sorry to bug you guys but having issues. my 78 sea ray has a 351 ford to a omc 800 sterndrive. i have rebuilt to holly 600 cfm carb, new fuel pump, new filters and fuel seperator. clean lines and checked vent. the dang thing runs perfect to about half to 3/4 throttle then about after 10 seconds into the plane boggs out and loses power. looks from what we see the secondarys on the four barrel arn't squirting. like lack of fuel maybe... pump is pumping good but there are some small air bubbles coming thru the clear fuel line directly from the tank to the filter/pump.. full tank of gas... I think it is a vacumm secondary is there somthing i am forgetting to hook up? or set? i have dumpped hundreds of dollars at this and still nowhere. here is a link to a youtube video of the bogg..
http://www.youtube.com/hucksterfool

 

[SCORPIO]

Its obviously fuel starvation, now as to a cause. Is your fuel tank vent blocked? If it is, it will bog like that. A clogged antisiphon valve will do this also. Could be a fuel filter clog. OH, I see you said there are bubbles in the clear tube from the carb to the fuel pump. Theres not supposed to be anything in there. Its designed to prevent a ruptured fuel pump diaphram from dumping gas into the bilge. Sounds like you problem is a bad fuel pump. You may have fuel in your oil too.

 

[SCORPIO]

I re read your post, and I have a question, what clear tube has bubbles in it? If its the main line from the tank to the pump, then you are sucking air probablly from a leaky fitting or a bad pick up tube in the tank. Most tanks have more than one pick up.

 

[ghuskin]

sounds like the fuel pump. try bypassing the fuel pump with an external (portable) tank, then see how she runs. If she runs strong, you've at least isolated your problem to the 1) fuel pump, 2) anti-syphon valve, or 3) fuel pick-up.

Good luck and let us know what you find.

 

[liftbridge]

This may be a long shot but I had a 1975 24 foot with a 351 OMC electric shift and I had a similar problem. As it turns out I was overheating at higher RPM's due to a worn swivel bearing not letting the water flow as it should to cool the engine . The higher the RPM's the hotter the engine got and it caused it to bog down. Good luck!!

 

[ypj]

i have a sea ray sundancer & the steering is seized. i think the the cable is the problem.can anbody help.:smt101

 

[hucksterfool]

rebuilt carb, new fuel pump, lines, still boggs i think there may be water in tank or somthing it will run all day no issues at half throttle but if i open her up 10 15 secs later boggs out to stall.it is somthing isolated to tank, pickup or water... I do have a water seperator tho aint helping...

 

[hucksterfool]

also does the tank puckup have a filter on the end? can i pull it out from back top of tank? i unfortunatly have alot of fuel in tank like 50 gallons

 

[ghuskin]

Yes, there is a screen. It can get clogged. Additionally, at the top of that tube is an Anti-syphon valve. Those go bad as well. maybe replacing 1 or both might do the trick. They are easy to do yourself and inexpensive. both parts come out as an assembly. Just remove the floorboard over the tank. You'll see it toward the stern side of the tank.

Let us know.

 

[pierseverance]

Try putting in a fuel pressure gauge inline up near the carb. Watch it at the point of cut-out. Start there and work your way back to the fuel pump and finally the supply line from the tank. Sounds like the anti-siphon valve in the supply line. Or.... heres an new thought....vacuum

 

[SCORPIO]

I watched the video and it sounds to me like you are sucking the carb dry under heavy throttle load. That says supply problem to me, filters, fuel pump, sucking air or even a clogged fuel tank vent.
I see you rebuilt the carb. Did it do this before the rebuild? You may just need a float adjustment, raise it and more gas will be available in the bowl. Has the boat ever run correctly since you've had it or is this a new problem?

 

[hucksterfool]

thanks guys for all your input, it ended up being the anti-siphon valve. replaced, runs like a champ!