very rough running 5.0L in gear up to 1500rpm

G

glocklt4

Member
Jul 31, 2008
447
Dallas, TX
Boat Info
200 Sport
Engines
5.0L Carb / Alpha I Gen II
2nd day on the lake this season today and had a problem with my engine running rough again. First time was Sat, and it only happened for a little while. It idled fine except a couple times. Putting it into gear at idle to troll was ok most of the time, but a little bit of gas and rpm's would either sit there, or go down and it would die or nearly die if i didn't put it back into neutral again.. If I gave it more gas, it would wake up around 2000rpm and be fine cruising around.

I asked a buddy out today and he mentioned that maybe it was overheating when going slow (possibly impeller problem) or I had bad gas. I watched temps and that was ok (170-190 my guess).

Not sure how to test the gas, but we burned about half a tank this weekend, so I was going to fill it up for next weekend to eliminate that as a possible problem.

Another option would be dirty carb, however it was not a consistent problem and got better later right before pulling the boat out of the water, no problems at all.

Since it jumped back and fourth between working and not working and I didn't change gas, that should eliminate that. Also the temp shouldn't be an issue because it looked fine to me after i started keeping an eye on it, and we were running around doing lots of tubing before we took it out of the water. It should have been the hotest at this time, but it was working perfectly.

Any ideas?? Doesn't make me feel good! Ignition?
 
Possible fuel filter is dirty. Your friend mentioned the water pump impeller. I see you have a 2005 boat. Have you changed the impeller? It won't cause the boat to run rough, unless very hot, but 3 years is the average.................
 
I changed the fuel filter at the end of the year last year, so I would expect it to be fine.

I bought the boat in August last year and have not changed the impeller, however I had a mechanic fully check out the engine and drive unit and the impeller was in perfect condition when we looked at it. Only 77 hours on the boat now, 58 when i bought it.

After doing some reading last night it seems more likely that it is the gas that's causing the problem. I'm not sure how that is going to be inconsistent like I've experienced though. Spark plugs are also another possibility. I will check them out tonight, however it ran fine last year and I only put about 20 hours on it since purchase with full check over.
 
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Didn't get a chance to check plugs since it was raining.

No more ideas though?
 
Spoke to another friend who says he has heard of this happening a couple times to different people due to bad gas. I followed directions from here to fill tank all the way up and add fuel stabilizer, so who knows...

Anyway, going to try adding premium in it when I go out this weekend. Still checking plugs first though just for kicks.
 
plugs are cheap. I change mine out every spring prior to launch. if your motor was "fogged" before being put up for storage, definately change the plugs.
 
ghuskin said:
plugs are cheap. I change mine out every spring prior to launch. if your motor was "fogged" before being put up for storage, definately change the plugs.
Click to expand...

Good point. I did fog the engine a bit. Will go ahead and change them out then.
 
Here's an easy way to check to see if you have water in your fuel: remove fuel filter, dump the fuel into a clear, glass jar. Let it sit overnight and observe it the next day.

Just because the filter was changed last year, doesn't mean it isn't clogged now.

Still may not be your problem, but it's a variable that's easily checked. I doubt adding premium is going to do anything. It might, but it would be best to ascertain the quality of the fuel that's currently in there, first.
 
Lazy Daze said:
Here's an easy way to check to see if you have water in your fuel: remove fuel filter, dump the fuel into a clear, glass jar. Let it sit overnight and observe it the next day.

Just because the filter was changed last year, doesn't mean it isn't clogged now.

Still may not be your problem, but it's a variable that's easily checked. I doubt adding premium is going to do anything. It might, but it would be best to ascertain the quality of the fuel that's currently in there, first.
Click to expand...

Will there be water sitting on the bottom of the jar?

Also wouldn't a dirty fuel filter cause high rpm problems more since that is when the most fuel is going through?
 
glocklt4 said:
Will there be water sitting on the bottom of the jar?

Also wouldn't a dirty fuel filter cause high rpm problems more since that is when the most fuel is going through?
Click to expand...

Yes, you'll see an obvious difference. It may even look "cloudy" when you first pour it out.

High RPM? Tough to say. I have yet to find a hard-and-fast rule. I think it's all going to depend on how it's picked up and the concentration.
 
Don't waste the dough on premium. If the engine isn't specifically designed for it you will get no noticable differences. Start with the easy stuff - fuel filter, plugs, plug wires, etc. Even only a few years old, things just go bad sometimes.
 
Just another thought - when it was winterized, and I'm using that term loosely since your in Dallas, did you treat the gas with a stabilizer? If not, that could be the problem, too. If not, siphon as much out as you can, then fill with fresh. But still dump out the filter, first - just to be sure.
 
Lazy Daze said:
Just another thought - when it was winterized, and I'm using that term loosely since your in Dallas, did you treat the gas with a stabilizer? If not, that could be the problem, too. If not, siphon as much out as you can, then fill with fresh. But still dump out the filter, first - just to be sure.
Click to expand...

Yep, winterized.

Fuel Stabilizer
Oil Change
Oil Filter Change
Fuel Filter Change
Filled up gas tank
Drive Oil change


One change made recently that I guess I should declare is the addition of a second battery, 800watt stereo system and combiner relay. Since it is either fuel or spark, i suppose that something to do with weird charging going on could cause ignition issues... so it's worth mentioning.

Keep in mind how sporadic this was though. Ran fine at first, then not so well for a while, then fine again... all within about 6 hours.
 
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Nehalennia said:
And to confirm it's a carbureted 5L?
Click to expand...

Correct. This is my first carbed engine and boat, so that's why i'm a bit unsure about how this all works.

I've rebuilt and programmed a 383 and 350 in two different C4 vettes i own, so I know a lot about engines, but nothing really about carbs.
 
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