bogging at high rpm after long day of trolling

[OHfishing]

Hello all once again I seek your advice.

I have a 1987 Sea Ray with a 260 HP mercruiser 5.7. I have used it for the last 3 weeks and it runs like a dream at idle and full throttle.

This past weekend I did some walleye trolling on Lake Erie , I trolled for 6 hours Saturday and ran 10 miles back in at full throttle.

Filled gas tank at marina with 87 octane, woke up Sunday ran back out 10 miles at full throttle no problems. Trolled once again for 6 hours at just above idle speed.

On the way back in I had some problems at full throttle, it runs fine at idle and fine up to about 3000 rpm, when I push it above that it bogs and sounds like it wants to die. I pull back on the throttle before it stalls and it runs fine.

I had to make the 10 mile run at half throttle, but I kept trying to go faster each time it bogged down until I pulled back.

Woke up this morning boat starts and idles perfect. I should also mention the fuel/water seperator was changed 3 weeks ago and carb was cleaned with gumout 3 weeks ago. This boat ran perfect until my long trolling trips. Damn walleyes!

Anyone have any thoughts?

 

[alldodge]

Hello all once again I seek your advice.

I have a 1987 Sea Ray with a 260 HP mercruiser 5.7. I have used it for the last 3 weeks and it runs like a dream at idle and full throttle.

This past weekend I did some walleye trolling on Lake Erie , I trolled for 6 hours Saturday and ran 10 miles back in at full throttle.

Filled gas tank at marina with 87 octane, woke up Sunday ran back out 10 miles at full throttle no problems. Trolled once again for 6 hours at just above idle speed.

On the way back in I had some problems at full throttle, it runs fine at idle and fine up to about 3000 rpm, when I push it above that it bogs and sounds like it wants to die. I pull back on the throttle before it stalls and it runs fine.

I had to make the 10 mile run at half throttle, but I kept trying to go faster each time it bogged down until I pulled back.

Woke up this morning boat starts and idles perfect. I should also mention the fuel/water seperator was changed 3 weeks ago and carb was cleaned with gumout 3 weeks ago. This boat ran perfect until my long trolling trips. Damn walleyes!

Anyone have any thoughts?

I think you need to pull the filter and check for curd. If its clean, no water and no crud, then that's good. Next check fuel pressure, should be between 4 to 7 psi. If that's good, then pull the carb and clean and rebuild it. If you sprayed carb cleaner on the outside and down the throat of the carb, it could help but would do very little.

 

[OHfishing]

Will any fuel additives help me?

 

[alldodge]

Will any fuel additives help me?

IMO, no, I see them as merely snake oil, but there are others here which would disagree. Additives are not bad sometimes for removing a slight bit of water, or keeping gas from going bad, but that's about it

 

[OHfishing]

Being that the boat was running perfect until 2 full days at idle speed trolling , I assume I caused this by trolling? Is this what I can expect from trolling with my mercruiser?

 

[duped]

I've put hundreds and hundreds of hours on my Mercruisers at trolling speeds and have never had that issue. I've fouled plugs and whatnot, but all it takes is a quick rev to "blow the cobwebs out"...

Sounds like you have some sort of carb issue.

Otherwise trolling on an I/O is great as long as you grease your coupler regularly and make sure your impeller is good. I've had weak impellers that would seem good in normal cruising but would give low RPM overheats.

 

[salty3rd]

A bad ignition coil could cause this as well..

 

[alldodge]

Being that the boat was running perfect until 2 full days at idle speed trolling , I assume I caused this by trolling? Is this what I can expect from trolling with my mercruiser?

It isn't caused by trolling, the carb will deliver fuel just fine all day long at slow speeds. As duped mentioned there could be some slight carbon build up on plugs but running back blowing it out would take care of that issue. Just need to figure out what is causing the issue, is it fuel or as Salty mention the coil. Do some diagnostic work and figure out what it is

 

[JaCrispy]

Besides the water separator there's a filter inside the carb at the fuel inlet. Says "filter".

 

[OHfishing]

I don't remember seeing a filter at the carb but I will give it a look. I will be going to the marina Friday and I will be changing the fuel filter seperator again and was thinking of putting some seafoam down the carb and letting it sit overnight. Would doing this possibly help clean whatever is clogged inside the carb? At least before I start removing or rebuilding things?

 

[JaCrispy]

I don't remember seeing a filter at the carb but I will give it a look.

You can't see it because it's inside the carb. You remove the fuel line, then with a 1" wrench remove the fitting the fuel line was attached to. Inside there is the filter. Any auto parts store will carry them.

 

[alldodge]

I don't remember seeing a filter at the carb but I will give it a look. I will be going to the marina Friday and I will be changing the fuel filter seperator again and was thinking of putting some seafoam down the carb and letting it sit overnight. Would doing this possibly help clean whatever is clogged inside the carb? At least before I start removing or rebuilding things?

Your issue is in side the carb if my assumption is correct. Don't change the filter, pull it off and dump the contents into something so you can see if there is crud or water in it. If there is either then yes change it

 

[OHfishing]

Before I read your reply I went to autozone and purchased another filter / seperator , seafoam (which was buy one get one lol) and some octane booster someone recommended. I am going to stop using 87 octane at the marina and buy the better stuff.

I do have a question, if something is clogged in my carb, can I pour in some sea foam directly into carb Friday evening at the dock and leave it in overnight? Saturday morning I will take the boat and give it a good run?/is this a good idea?

 

[alldodge]

Before I read your reply I went to autozone and purchased another filter / seperator , seafoam (which was buy one get one lol) and some octane booster someone recommended. I am going to stop using 87 octane at the marina and buy the better stuff.

You mean (IMO) your going to start spending more money for fuel. High octane does not burn hotter or better, it burns slower only. The only folks that need higer octane fuel are folks which have higher compression engines, the higher compression causes more heat and cause lower octane fuel to ignite before the spark hits it.

I do have a question, if something is clogged in my carb, can I pour in some sea foam directly into carb Friday evening at the dock and leave it in overnight? Saturday morning I will take the boat and give it a good run?/is this a good idea?

As before IMO additives are snake oil. The first thing folks do when they have a problem is put seafoam in the tank, sure wish I would have bought stock in the company years ago. Seafoam does not burn very well, so putting it inside the carb (if you can get it in there), will do nothing but make it harder to start until it gets push through and out. This is just my opinion, its your boat, your decision.

 

[alldodge]

We still don't know what the exact issue is but I believe its in the carb. Also don't know what carb you have. If you can remove the top of the carb without damaging the gasket, remove it. Look down in the carb and see if you see any crud. Fill the bowl up with carb cleaner like Gumout or the like, and put the top back on. Once back on, pump the accelerator pump a few times to get it through that port and let it sit.

If you don't want to remove the top, remove the fuel line. Pump the accelerator pump until nothing comes out. Now try to pour the carb cleaner in thru the fuel line inlet. Get it full, pump the accelerator a few times to pump it through, then let the rest sit. Put the fuel line back on and wait till morning

 

[Bondo]

I will be going to the marina Friday and I will be changing the fuel filter seperator again and

Ayuh,.... For diagnosis purposes, ya Gotta check the Contents of the take-off filter,....

Ya might just have a slug of Water,.....

Alway, Always, check the Contents, of take-off filters, they tell a story,....

I use a freezer baggie to catch spills takin' the filter off, drop it in, seal it up, 'n flip it over,....
A nice clean window to view the contents of the filter,....

'n No,... Pourin' stuff over the carb don't do Nothin',....

Carbs are cleaned, 'n rebuilt by complete disassembly, 'n cleanin',....

 

[OHfishing]

To be honest, I think the reason people on this board like me gravitate towards seafoam and other snake oil remedys is (please bare with me) I'm not mechanically inclined. My boat is 2 hours away at a dock, my worst nightmare taking the carb off and rebuilding it which may be a walk in the park for others. Something like ignition problems or testing things that we don't know what they are or where to look or have voltage testers etc etc and the know how. However spraying gumout or seafoam I am comfortable with. Heck I'm embarrassed to tell ya I'm praying I can find this inline filter at the carb. I think a lot of guys on the board are praying for a simple seafoam fix.

Thank each and every one of you for helping guys like us.

 

[OHfishing]

P.s. the gallon size ziplock bag is a fantastic idea, thank you!
Would it be common for a fuel filter to be full of crud 3 weeks into boating season?

 

[alldodge]

P.s. the gallon size ziplock bag is a fantastic idea, thank you!
Would it be common for a fuel filter to be full of crud 3 weeks into boating season?

It is an older boat so there is the possibility, were just trying to figure out what the issue is as you are. Are handicap is we cannot lay hands on the engine.

I'm praying I can find this inline filter at the carb

We could tell you where it is if we knew what carb you have. Here is a link to a rochester carb for your model year and if it is the same it is item 2 in link below
http://www.mercruiserparts.com/Show...br=140&bdesc=CARBURETOR(ROCHESTER+-+4+BARREL)

 

[Bondo]

Would it be common for a fuel filter to be full of crud 3 weeks into boating season?

Ayuh,..... Who knows what's in yer tank, or how often the vent is splashed, or how it's plumbed,.....

My ole tinbarge had it's vents in the spray, with no Up loop in the line,....
My fuel filters were Fulla water all the time, til I figured out, Why,.....

The Up loop in the line allows any splashed water to run back Outa the boat, insteada into yer fuel tank,...