Omc 5.8 issue

[Hildebrand]

Hi, I'm a new boat owner and had a issue tonight. Before I take the boat back out I wanted to ask some questions before I got stranded or anything. 1990 Four winns 5.8 omc cobra. Boat does start hard cold , but I've been told the cobras are cold blooded. Took the boat out and everything was normal. Went to come in from fishing and the lake picked up and was pretty choppy. Was headed in 25 mph in and out of waves and I thought I noticed a slight power loss so I throttled down , boat still running good. I went to take off agin and had massive bogging down like it was hot. I checked my temp gauge and it was between 180-200. As idling still, running clean I pulled the cover to the engine and nothing seemed hot or like it was overheating but it was acting like it was and reading warmer than normal. I wasn't very far from the dock so I was playing with the throttle and when I was almost full it would go and got me back to the channel and through the channel it ran perfect at2-3 mph. Could I have gotten water in my gas, we did just have a some rain, and the gas gauge is reading a quarter and that's as low as I have ever run it. I am new to boating, so wanted to ask. Thanks

 

[southkogs]

Welcome aboard.

Sounds like you're running hot. I'm not sure what operating temp is on a Cobra, but I would guess in the 160 - 180 range. When did you last change the impeller?

 

[Lou C]

180-200 is too hot. They come with a 160* stat just like most Volvos and should run from 160-175. There is no reason for the engine to be hard starting cold as long as the engine is in good tune and the auto choke is working properly. That's a Ford 5.8 and it most likely has a Holley carb with an electric choke. When you start it are you pulling the control handle out so that the shift system is disengaged and you can advance the throttle in neutral? The way you start these cold you pull the handle toward you (if its an OE OMC control, others use a push button) and advance it all the way forward, that allows the choke to close or nearly close. Then you pump the throttle and leave it set at about 1/3 advanced to set the fast idle. Marine carbs do not automatically set a fast idle like an auto carb would.
​You need to go through the fuel, ignition and cooling system on this boat.

 

[Maclin]

Above 180 is starting to overheat and could affect how it runs. Regarding water in the gas, water will be at the bottom of the tank, full or not. You might check the water separating fuel filter if it has one.

 

[Hildebrand]

I could not tell you about the impeller as I've had the boat since July. It was on my list of things to do this offseason along with a cap,rotor,plugs,wires and a fuel filter. I've never done one, but it doesn't look like a terrible job to change one. Yes, the boat has a Holley 4 barrel carb with electrictronic choke. I'll ingage the choke about half way and try to fire it up and I'll have to play with it for a bit to get it to fire and after that it's fine.

 

[Scott Danforth]

Cobras are extremely easy to change impeller. That should be the first thing anyone does with a used boat.

Lou has you covered on starting

 

[Hildebrand]

I just looked up on the impeller, and that is going to be addressed before the boat hits the water agin. As for the cold start, I'm going to look into this. I'm not very knowledgeable with carburetors , so I'm going to read up and ask a lot of questions. For the electronic choke, how can I tell if it's working properly? I know if I engage the throttle I can see two nice squirts of gas in the carb.

 

[Maclin]

It is not "electronic" choke. It is electric, which means the choke mechanism has an electric heating element to aid in pulling open. So, on a dead cold engine the top choke flap should be resting in a closed state with a little bit of spring pressure. The pivot is offset, and if you poke the "long" side it should move pretty easily but snap back closed. When the ignition is on the choke heater coil begins to heat up and uncoil and this moves the choke plate gradually to the open stance which is straight up and down in the bore.

On the side of the carb you will see a round black housing, that is the choke heater with coil inside. On the outside you will see L and R settings for Leaner and Richer. If the choke when cold is not closed all the way the adjustment needs to be Richer. If when in use your engine does not like how long the choke stays on then the adjustment needs to go Leaner.

 

[Hildebrand]

It is not "electronic" choke. It is electric, which means the choke mechanism has an electric heating element to aid in pulling open. So, on a dead cold engine the top choke flap should be resting in a closed state with a little bit of spring pressure. The pivot is offset, and if you poke the "long" side it should move pretty easily but snap back closed. When the ignition is on the choke heater coil begins to heat up and uncoil and this moves the choke plate gradually to the open stance which is straight up and down in the bore.

On the side of the carb you will see a round black housing, that is the choke heater with coil inside. On the outside you will see L and R settings for Leaner and Richer. If the choke when cold is not closed all the way the adjustment needs to be Richer. If when in use your engine does not like how long the choke stays on then the adjustment needs to go Leaner.

Thank you for clearing that up for me. After use the boat starts pretty easy, most times just little to no choke and it fires up

 

[Hildebrand]

Also, I will be picking up a impeller and a set of muffs today. Once the impeller is done I'll begin to check fuel and ingnition

 

[Hildebrand]

So I just changed the impeller. Mine didn't look bad in my eyes but truthfully I couldn't tell you either way. Mine didn't have pieces or anything missing. I did get a set of muffs and fire the boat up. I throttled down three times and left the choke about 1/4 way and it fired up no issuse. I've never fried it that way, always just choked it.

As for a tune up, the boat needs one. The wires say 1989 on them and my boats a 90 so I think they are original lol I had the boat running on the mufffs and I touch?d the coil wire at the cap and it whacked me pretty good, donuts arcing out. The plugs looked old too.

 

[HT32BSX115]

Thank you for clearing that up for me. After use the boat starts pretty easy, most times just little to no choke and it fires up

Howdy, Automatic chokes are really overrated IMHO....

If your engine starts easily and runs well once warmed up, you may not have to rebuild your carb at all.

Let me also add that I have been operating my 454 with the automatic choke disconnected and adjusted completely out of the picture for over 10 years.

After the boat sits for 9 months or so, Instead of cranking to prime the carb, I pour a little gasoline down the carb initially to get it running at the beginning of the "season" because the carb is usually completely dry, but once it gets running, it starts fine after a couple of accelerator pumps of fuel. No choke needed.....

I only boat during summer in warm weather so it's never a problem with subsequent "cold" starts.......if you want to be able to boat during late fall/winter/early Spring or other times in cold (non-swimming) weather, you'll probably want to have a properly adjusted choke.

Regards,

Rick

 

[Hildebrand]

On muffs yesterday, which was a cold start I hit the accelerator pump 3 times and left the handle out and 1/4 way and it started right up. I think I was just doing it wrong from the get go,as I am new to the boat life.

 

[Lou C]

Sounds like you're getting the hang of it! Some of us, of ah a certain age learned how to drive on cars with chokes, so for us, its kinda second nature...
​Personally I would not mind a purely manual choke for my QJet, if I could find a conversion kit that was not a flimsy piece of junk! My auto choke works as well as it can, but they open a bit too slowly because of the fact that marine engines run about 35* cooler than an equivalent auto engine....

 

[Maclin]

Iboost23 You may just be new to "living with a carburetor", getting to be a lost art I had not thought about that when I posted, usually I ask about the actual starting procedure with the throttle and give a suggestion or two. HT covered for me!