Boat bogs down when cruising, can't find the problem

[dbobz71]

1997 Maxum 1950SR
4.3l Vortec 2bbl/Alpha 1 Outdrive

So the past couple times when i have been out on the river after about 3-4 hours (i'm always headed back up river by this point) the boat will bog down any time i try to go over about 15 mph. i can sustain about 5-10mph but if i try to go any faster it will bog down eventually and sometimes die, i also noted that it will not maintain a constant speed above 5-10mph (i assumed that was due to traveling against the current). I really have not worked much on carburated engines and never on a marine engine/carburetor.

Usually when i start having this problem I am about half tank or lower and it is when i am trying to come back up river from the ocean to where i put in at. I checked the oil thinking there might be water in it but the oil is a clean and looks new (carmel color)

The only other problem with the engine is that the guy before me said he was having problems with the starter and ended up putting a second battery in the boat to fix the problem, i have been meaning to fix this but was hoping to wait untill the end of the season.

Any help would be greatly appreciated or maybe pointers on what i should check as i am kinda just easter-egging my way around checking stuff.

 

[mark1905]

Re: Boat bogs down when cruising, can't find the problem

Sounds fuel delivery/pump related to me.

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

Sounds fuel delivery/pump related to me.

do you know if fuel pumps are something marine specific or can a auto one be used if i do end up having a problem with the pump itself?

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

Does anybody know what this part is?

the mount for it is corroded and it just sits there now, i don't know if it is the cause of the problem but i am having a hard time finding out what it is so i can find a new mount for it

 

[abrx7]

Re: Boat bogs down when cruising, can't find the problem

That is your hydrolic pump for the trim

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

alright, so after talking to some guys at west marine they said my problem might be from the ethanol in gas at the pumps, so i filled up the tank and put some sea foam in it, my plan is when it gets empty to refuel with the additive for ethanol, it isn't bogging down unless i try to put it full throttle at any speed, and will maintain a speed now, it also back fires when it bogs down and then picks up speed again.

anybody have any ideas if i chasing the right path? i also have been kind of thinking that it only bogs down bad when it gets down to under 1/2 tank if that matters any.

 

[1ruralmailman]

Re: Boat bogs down when cruising, can't find the problem

fuel pump needs to be marine specific to keep fumes contained,as well as the return from carb is different.

 

[mark1905]

Re: Boat bogs down when cruising, can't find the problem

alright, so after talking to some guys at west marine they said my problem might be from the ethanol in gas at the pumps, so i filled up the tank and put some sea foam in it, my plan is when it gets empty to refuel with the additive for ethanol, it isn't bogging down unless i try to put it full throttle at any speed, and will maintain a speed now, it also back fires when it bogs down and then picks up speed again.

anybody have any ideas if i chasing the right path? i also have been kind of thinking that it only bogs down bad when it gets down to under 1/2 tank if that matters any.

:facepalm:

This is why the guys at West Marine are standing behind a counter ringing up water wings instead of fixing boats for a living.

If it's TRULY only when it's less than half full, then it sounds like you may have some kind of pickup or fuel quality issue. You're saying that with all certainty that it does not matter if the engine is hot or cold, that the only deciding factor on whether or not the engine does this is what your fuel level is like? With complete confidence?

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

i am pretty sure it has to do with the fuel level, i filled it up and put the sea foam in it and it didn't run any differently but it bog out on me, im not under half a tank yet though so next time i take it out im gonna see if it is the fuel level, is the fuel pick-up something that is hard to diagnose, i thought i had read somewhere that it might just be sludge built up on it that you an wipe off.

 

[DarrinT]

Re: Boat bogs down when cruising, can't find the problem

Check the fuel lines especially in the tank(s)

Buddy of mine had the exact same symptoms and it turned out to be a crack in the line in the tank that would suck air under high fuel flow conditions stalling the engine. The crack would then close and it would start right up!!!!

Made him bonkers for two seasons before he found the flaw beacuse with a full tank the crack was under the fuel so this problem was only intermittent under the condition of lowish fuel and WOT

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

Check the fuel lines especially in the tank(s)

Buddy of mine had the exact same symptoms and it turned out to be a crack in the line in the tank that would suck air under high fuel flow conditions stalling the engine. The crack would then close and it would start right up!!!!

Made him bonkers for two seasons before he found the flaw beacuse with a full tank the crack was under the fuel so this problem was only intermittent under the condition of lowish fuel and WOT

damn means im gonna have to take out the tank just to check, thank you though for the tip

I have been checking my fuel/water separator and every time i take it out it is full of water, my dad said on his boat his never collected water. does anybody else have this problem? Could it be the gas i put in it? (87 octane/10% ethanol)

 

[dbobz71]

Re: Boat bogs down when cruising, can't find the problem

okay so i have a theory, my fuel vent for overflow is right next to the filler hole which is located right above the swim platform, when i stop the boat in the water the water rushes up the swim platform, sometimes even up to the actual seats. I think that water is rushing down that vent hole and into the gas tank. So this water is building up in the gas tank every time this happens. My theory is that it takes about two hours for the water separator to fill up, once it is full it prevents regular gas flow hence the reason i can only go about ten mph. But when i empty it, it runs just fine.

So to fix this i need to get the water out of the tank, empty the separator of course, and either be careful when stopping or relocate the vent.

feel free to comment if this doesn't seem logical

 

[81 Checkmate]

Re: Boat bogs down when cruising, can't find the problem

Sounds like you have found your problem.

Clean out tank... get a hand pump or elect.. pump out tank.
Change separator and fuel filter on carb.
Relocate vent line...... a must..

Refill with gas and sea foam..

It's what i would do.

Good Luck!