5.8 omc not running right

[Hildebrand]

90 omc cobra 5.8 put 40 gallons in it this morning and took it out on the lake for fire works tonight. Ran the boat about 4-5 miles out to swim, boat ran fine. Loaded up from swimming and just after getting on plane the boat bogged out, Then it would
clean up for a few seconds and do it agin. It was like I was letting off the gas. Boat would idle fine and start without a issue. It didn’t seem to matter what rpm range I was at or speed it did it. It was random and would clean up for a few and do it.

Things I have done in the past year.
spark plugs
wires
fuel filter
impeller
oil change
t-stat
belts

 

[southkogs]

Clean the carburetor? Maybe an air/fuel mixture issue?

 

[Scott Danforth]

or water/crud in the fuel

 

[Hildebrand]

The fuel hose from the tank to the filter was dry rotted and broken. I’m am replacing that now. Could this be a vent issue ? No problems at low idle tho

 

[Hildebrand]

I am also going to pull the fuel filter off and check it. I put that on about two weeks ago or so.

 

[Hildebrand]

Pulled the fuel filter and no water or dirt in it. Pulled the little hose that comes to the tank next to the fill line and air goes through it.

 

[Hildebrand]

So I took the boat back out just now to see if anything changed with the little things I did. It wasn’t as bad but it tried to act up. I had the floor off over the tank and you could hear like a wine/buzz sound from the tank st random. Also the boat would not get over 4K rmp. It just feels like it’s missing a touch of power.

 

[Hildebrand]

Can anybody point me in the right direction on this ? Could the pick up tube be causing me issues and making that noise ? Also, do you just disconnect the wire and unbolt the pick up and pull it out?

 

[Hildebrand]

So after a long day on research, I pulled the float out because I had no idea what was down there. I checked it all and checked out good. I pulled the pick up tube and the screen was clean and I could blow down the pick up tube. The anti siphon valve was really really sticky and didn’t work good. Maybe, just maybe that was causing me issues. Couldn’t get has gas at high speeds when warm. Not sure but it’s replaced. Even if it doesn’t fix it it was worth the 11 bucks for a new one. Next I bought a new coil bc maybe mines getting out and messing up. Mine is the original from 1990 so it could be taking a crap. My question is, what wires hook up to the positive and what to the negative ? The old coil isn’t marked. I know I have been talking to myself l,. It maybe this will help a fellow boater one day. Thanks

 

[Hildebrand]

I know nobody is posting here but I am bc I hope it helps somebody one day. I changed the coil siphon valve and I started on the muffs. I know I wasn’t able to get a full load but it still didn’t sound right. It seemed a little off. This afternoon I took it to my local marina, they are still really bit into omc stuff. It’s a 2-3 week turn around time but hopefully I’ll get some news. Once I know I’ll post back

 

[Scott Danforth]

Its never the coil you wasted money

A coil either works or doesnt

Go back to the fuel system, you have wster or crud somewhere

Since the Anti siphon valve was full of crud, your fuel tank and carb have the same crud

Clean the tank
Clean your carb

 

[Hildebrand]

Thanks for getting back. Yes, I probably did but it was original, was getting really hot after running it so it was just a process of elimination. I will go over the carb and tank. Thanks

 

[Scott Danforth]

they run hot. about 10-15 degrees warmer than the motor they are bolted to

so with a motor running 160, your coil should be about 170 or so

 

[Hildebrand]

Makes sense now that you say that. Wish I would have checked the temp with my temp gun before swapping. Anyways, can’t take it back. I am going to clean the carb and possibly look for a rebuild kit. Can’t hurt to rebuild it. Thanks agin

 

[Hildebrand]

Wanted to bring back up old post from last year. I ended up taking the boat in and they could not find anything wrong. So I thought the coil I put on fixed it. So I have used the boat all summer and this weekend it did it again. It was after a run out and fished for a little bit trolling with the big motor and then it did it just before we hit the channel in. My temp gauge was ready about 170. It was 95 out and the lake is extra warm this year because all the hot weather we have had.

The carb has been cleaned,the fuel filter has been changed. Plugs and wires are only 2 years old. Could a plug be fouling out ? Should I pull them and get a tighter gap ? Any ideas here ? To be something is getting hot but I dont know what or how. Its not showing sings of overheating

 

[Scott Danforth]

did you ever clean your tank?

 

[Hildebrand]

Yes, tank cleaned, checked vent and replaced fuel lines just to be safe. It basically happened this time last summer too. So when the water and temp is really hot. My IR gun showed 162 in the risers why on plane.