OMC bogging/power loss issues

[nportwine]

Have a 1988 Four winns 215 Sundowner with a 5.0 OMC GM 305. Have had this WOT bog problem to where it will run good and have tons of power up until like 85% of throttle, if you go past that it will bog down and sit at like 2500-3000RPM. If i accelerate slowly, I can get it up to around 4000. I have replaced all fuel filters numerous times, sometimes it does seem to help a bit. I have replaced the anti siphon valve, fuel lines, cleaned the fuel sender and inspected the tank. The boat has a electronic distributor kit on it,and timing seems to be correct. Also the PO had the outdrive rebuilt, and a bit lower of a gear ratio put in it to help with planing. Temp runs about 170 ish. It seems to get worse after running all day, and will have trouble pulling a tube after a few hours. I dont want to start throwing parts at it, but have been dealing with this issue for a long time and want to get it resolved. Thanks in advance!

 

[Scott Danforth]

pull your carb, clean it inside and out, and put a new carb kit in it. the bog is from crud in your carb blocking passages and affecting your accelerator pump circuit.

check your cooling system as well.

 

[Lou C]

And lastly if the anti siphon valve on the gas tank is original, it could be restricting fuel flow, this one is missed by many people!
In fact when I first got my boat in '02, I had a similar problem (even worse) the engine would start and run fine in neutral but would not plane out the boat. I went through it myself but the mechanic found a bad anti siphon valve. That was the main cause although over the years the carb needed to be rebuilt 3 times. Seemed to average 6 years between rebuilds.

 

[nportwine]

And lastly if the anti siphon valve on the gas tank is original, it could be restricting fuel flow, this one is missed by many people!
In fact when I first got my boat in '02, I had a similar problem (even worse) the engine would start and run fine in neutral but would not plane out the boat. I went through it myself but the mechanic found a bad anti siphon valve. That was the main cause although over the years the carb needed to be rebuilt 3 times. Seemed to average 6 years between rebuilds.

I was hoping that would be the case with mine, but replaced it last year with no luck

 

[nportwine]

pull your carb, clean it inside and out, and put a new carb kit in it. the bog is from crud in your carb blocking passages and affecting your accelerator pump circuit.

check your cooling system as well.

I bought a kit awhile ago, my experience goes about as far as snowmobile and dirt bike carbs though. Is it something I can tackle myself?

 

[Scott Danforth]

similar complexity to any other carb out there. if its a holley or a rochester, there are specific carb sites that have how-too videos. stay away from you-tube as most of the amature vids are wrong.

key is take pictures before disassembly and follow the kit instructions.

 

[kenny nunez]

Another place to look is the inside of the fuel tank suction tube. Sometimes there is a fine screen inside of the tube. If you can pull the tube out and there is a screen just remove it.

 

[nportwine]

Rebuilt carb, probably could’ve done a better job cleaning so may do it again. Boat ran a lot better, will hold much higher rpm now, still seems to not be able to hold full wot rpm but it holds 4,000 which is much better. I used it for a few days and then I seemed to have more trouble getting it to plane off when fishing yesterday. We were cruising and stopped to check depth and after that we could not plane off or accelerate over like 1,000rpm. Only way to get the boat planes off after that was to have a buddy manually hold hold the primary partially shut and slowly move it open as I accelerated. It also made a loud whistling type noise when this issue occurred and the motor seemed to shake alot, but once up to speed it then ran okay if it didn’t move the throttle much. Hopefully this isn’t too big of an issue

 

[Lou C]

Ahhh….do you mean....that your buddy had to partially close the choke plate to get the boat to plane out? If so then the carb is still clogged or set too lean.
What carb do you have? A 1988 OMC with a GM engine should have a Rochester carb, either a 2bbl or 4bbl. The 2bbl is pretty simple to rebuild, the 4bbl (Quadrajet) is a bit more complex but overall not hard...I did mine at the end of last summer...

 

[nportwine]

I pulled carb off and replaced base gasket, planes out pretty good now without any manipulations of the choke. I replaced the spin on fuel filter as well. It idles rough but I think my mixture screws need to be adjusted to fix that issue. When I take off for the first run of the day, it planes out and runs good, holding atleast 4,300 rpm. Any runs after that especially trolling for a bit, itll run up to 4000-4300 rpm and then slowly lose rpms, itll usually atleast hold near 4000, but you can hear and feel the motor get surges of power and then lose it and itll do this continuously, if I slow down at all many times i wont be able to speed back up unless i stop for a second and then "re-plane" out. I have checked fuel tank, replaced all filters, replaced some of the fuel lines, the antisiphon valve, and gone through the carb. Boat does have a pertonix kit and timing seems to be correct. Hate to just keep throwing parts at this thing, it works for what I use it for but it gets really frustrating with the lack of power when trying to pull tubers and stuff. I have also tried running with fuel cap off to rule out any tank vent issues.

 

[nportwine]

Also seemingly unrelated info in my opinion but may be of significance to someone with more knowledge, the motor loses a significant amount of power when adjusting the trim under load.

 

[nportwine]

Found out coil was replaced when the pertonix kit was put in it, all this has me leaning toward the fuel pump being weak, but havent noticed any fuel in the oil or any in the clear hose between the pump and carb

 

[nportwine]

I noticed my oil seemed a little over full and smelled like gas, pulled fuel pump off, obviously the original pump from 1988. The diaphragm looks okay, no holes or tears, but the spring and area around it is super rusty, and the area that goes to the rubber fuel line that goes to the carb was completely blocked with crud. Do they sell a diaphragm kit? Or what would the replacement pump be? I can’t find anything online. It’s a carter 02208

 

[nportwine]

 

[nportwine]

Well I ordered a new full pump, old one actually seemed okay but figured it would be good preventative maintenance. To add another twist to this, I checked out my exhaust flappers for the first time after reading some other threads, both are intact, one moves freely, the other takes quite a bit of force to open and does not snap back Shut all the way. Am now curious if my issue that seemed to be a fuel restriction was maybe an exhaust restriction this whole time

 

[Lou C]

Also seemingly unrelated info in my opinion but may be of significance to someone with more knowledge, the motor loses a significant amount of power when adjusting the trim under load.

that problem is likely to be old corroded battery cables, I had that when I first got this boat but I put in a dual battery system with new cables about 15 years ago and haven't had that problem since. Also check the terminals on the trim relays, if water leaks on them in the motor box they will also get corroded. Make sure your battery cables have good clean terminals including the ground on the engine bell housing (behind the exhaust hose).

PS still don't know what carb you have. 2bb or 4bbl. Either one if original should be a Rochester.

PPS my old fuel pump looked just like that, diaphragm not leaking yet but all crudded up inside. I replaced it with a Sierra. Have fun with the push rod, that likes to slide out. Hopefully the V8 still has the provision to put a longer bolt in temporarily to hold the rod in place. The V6 like mine does not so I had to use thick grease and bad language to get it done!

 

[nportwine]

that problem is likely to be old corroded battery cables, I had that when I first got this boat but I put in a dual battery system with new cables about 15 years ago and haven't had that problem since. Also check the terminals on the trim relays, if water leaks on them in the motor box they will also get corroded. Make sure your battery cables have good clean terminals including the ground on the engine bell housing (behind the exhaust hose).

PS still don't know what carb you have. 2bb or 4bbl. Either one if original should be a Rochester.

PPS my old fuel pump looked just like that, diaphragm not leaking yet but all crudded up inside. I replaced it with a Sierra. Have fun with the push rod, that likes to slide out. Hopefully the V8 still has the provision to put a longer bolt in temporarily to hold the rod in place. The V6 like mine does not so I had to use thick grease and bad language to get it done!

Thanks Lou, I will check out my battery cables and was curious what the trick was to keep that push rod back long enough to slide the pump in, never thought about using some grease. The carb on it is a 4bbl Rochester. Taking the day off of work tomorrow to hopefully fix the flapper and pump and take it out for a test.