Engine won't get past 1500 rpm

[bluedolphin]

Hi, all.
1972 22-2 Aquasport. 1992 Mercury V6 200 hp.
Yesterday, I fired her up, and it will rev all the way up to 5000 rpm.
However, when I try to advance the throttle in gear, it sounds labored, and will not go past 1500 rpm. I can advance the throttle past 1500 rpm, but the boat does not go any faster, and the engine seems to want to sputter and stall. There is nothing wrapped around the prop, and the prop spins easily. Someone told me check the water/fuel filter and drain any water, if any. There was no water in the filter. It's one of those with a see-through bowl at the bottom. Anything else I can check? Thanks.

[RickK]

When I test drove my boat I had it out about 20 minutes and all of a sudden the motor throttled down and wouldn't run more than 2500rpm - ended up being a oil level sensor on the motor - seems the computer board went bad in the motor and didn't tell the remote oil tank to pump oil, so the on-motor tank ran low and that caused it to throttle down to protect itself.  It stays under 2500 to protect itself.
Might want to check that?

[bluedolphin]

Thanks, Rickk. I mix oil manually, I don't have an oil reservoir. Is it possible my fuel/oil mixture is not right? I use 50:1 which is the recommended ratio.

[RickK]

Ok, so that's not it - the mixture is correct.  Maybe browse the marine doctor's site and see if the answer is there or post the same question to him.

[GoneFission]

Sounds like it could be a faulty switchbox.  There are two and each powers 3 cylinders.  You will probably need to take it somewhere where they have one of the Mercury ignition testers to be sure.  The Mercury ignition is hard to troubleshoot without the factory tester.

[bluedolphin]

Thanks, Rickk and Cap'n John!
I will have the switchbox checked hopefully by the weekend so I can use the boat for the Air and Sea Show.

[fnichols]

Same thing is happening with my 4 strroke.  I checked to see if the bulb was okay and it was, then I pulled the plug cables one at a time while running.  Only noticed 1 cylinder firing.  However, I've been told that some motors only use one cylinder until you raise the rpms.  So i put the plugs one at a time next to the block to see if I was getting a spark.  Two of the plugs don't spark so I think I have a bad power pack like the guy said above.  Time to take it to a real mechanic and let him hook it to his diagnostics to see.

[RickK]

Same thing is happening with my 4 strroke.  I checked to see if the bulb was okay and it was, then I pulled the plug cables one at a time while running.  Only noticed 1 cylinder firing.  However, I've been told that some motors only use one cylinder until you raise the rpms.  So i put the plugs one at a time next to the block to see if I was getting a spark.  Two of the plugs don't spark so I think I have a bad power pack like the guy said above.  Time to take it to a real mechanic and let him hook it to his diagnostics to see.

I thought that motor wasn't that old?

[bluedolphin]

Finally got the mechanic to check the boat out two days ago (Saturday the 12th). I was not home but he knows where I leave the key. Anyway, he called me and said the boat ran fine, got it up to 4000 rpm no problem. I was ecstatic of course, because I did not have to spend any more $'s. But wait, I got home and I took the boat out to see for myself. It worked great for about 15 minutes, and then the trouble started all over again. Then the boat stalled, and I could not re-start. Fortunately, I was just out on the river with seawalls all over the place, so I drifted and managed to snag one of the dock cleats on one of the houses. Called the mechanic, he drove to the house where I was tied up to the dock. He managed to start the boat, and he checked the carburetor operation with the cowl off. He says that the carbs are flooding and need to be overhauled. There was a gas sheen on the water trailing the boat as we ran it. I told him about the switch box but he seems sure that the carbs are the culprit. Stay tuned. He will have the carbs back on the boat before the next weekend.

[JimCt]

I'd vote for carb problems; possibly weepy float valve(s) or a sunk float.  Rebuilds every few years are a fact of life with outboards.

[Ben87]

I may have posted this before but it was the bane of living with the 1987 150hp BlackMax I had for 19 years.  I will share my experience with you and this might be long.  

I would have the same symptoms as you did, especially the first time it ever happened.  The motor would rev fine out of gear but once in gear it would only go up to a certain rpm.  Sometimes it would "catch" and run like it was fine then go back to a 1,500 rpm or lower and not be able to get back up again.  Pull it out of gear and it would rev fine.  

We would go through the Clymer/Hynes and check everything until we found out what it was each and everytime and not once in the 19 years did we ever have to do anything to the carbs and we would be winterizing this engine every season from October/Nov. - May or June.  Just like when working on dirtbikes/2 strokes, they always say to check the carbs last.  I can imagine that just because I never had a single issue and never even touched or looked at the carburetors on my 150 for 19 years doesn't mean you might not have anything wrong with yours.  At least with dirtbikes, they say if it ran fine and doesn't anymore, don't start playing with jets and such because a single carburetor does not just go out of adjustment, now with 6 something could but who knows.  

On these Mercury's and I suspect like every outboard motor with CDI ignition, the stator lives under the flywheel.  The cooling systems on these engines was not all that great back then, at least I know it wasn't on my 87 as it had no way to flush and we kept the boat on a dock for at least 5 months out of the year and never flushed it save for running the motor to winterize it in the fall and start it in the spring, and all the heat generated by the block radiates up and as the stator lives under the flywheel, no matter what Mercury tried to do to increase the size of the laminations/windings on the stator which I was told by the parts people that mercury did to try and cure the problem, the stator would, in time, fry itself.  It is why when the engine is cold it will run fine, once it heats up it acts up eventually to the point where we would be stranded and the engine would do like it is doing to you or just not start until it cooled down.  Several times when our headaches began in the early 90's we would get towed in after out at sea we would change the fuel filter and the plugs and still not get the motor started, then we would tie up after a 1-2 hour tow and the motor would fire up and run fine until it got hot then it would act up again, it would drive me/us crazy back then.  

I got so good that I always carried a new/spare stator $160, the flywheel puller, the socket to get the flywheel nut off, the allen wrench to get the stator off, the philips screwdriver to get the switchboxes apart and the 8or10mm socket to get the wires off the switchboxes.  I had the process down so well I could be in 3-5 foot seas or in a rip or in the fog at night with no light and be able to swap out that Gosh Darned stator.  It was never a matter of if, it was when it would go.  I could put a new waterpump iand thermostats in every season, monitor the engine temp and the stator would go, there was nothing I nor Mercury could do to stop the stator from frying.  Oftentimes I would do a preventative swap once the engine would not start warm/hot on the first try and it would be time to swap the stator out.  

The first time we had to deal with the problem and I finally traced it to the stator using the book and finding out that no one, even the Mercury guys, could test the switchboxes, I replaced the stator, the coils and the switchboxes just to be safe, it was around $600 to do that but then it was good for the next 10 years or so.  Use the manual and check the stator leads, if any of the readings are not within spec, then you will have to replace it.  Once you have an ohmeter and know which leads to touch what to it is easy.  The switchboxes also live on the side of the engine block but I never had an issue with mine although I had heard that they go too but also spoke to Mercury and not a single dealer had the thing that could test them and this was back in the early 90's when the engine was only about 5-6 years old, I can imagine now that unless a dealer is good, they might not know what you are talking about, then again, here in Falmouth MA where there are not a whole lot of boats like there are in FL, we just don't have what FL has for dealers.    

Anyhow, it might not be your stator but after seeing so many motors of my vintage in the shop way back in those days, and each and every one of them back in there for stator replacement, I surely and unfortunately had my experience with them.  It could be fuel as well.  I just share what I know and what would happen to me on a regular 3-4 year cycle.  With all the running changes Mercury had on their motors back then, gee, the book I had had running model year changes in the engines every 6 months to try and "improve or modify" something, I memorized my serial number from needing it to get parts because 87 could have been 86 1/2 or 87 1/2, it was crazy back then with all the changes within model years because there was not CAD/Computer Aided Design like we have now where they could test things better or design things, they just did things and WE tested them to see if it would work or not.  

I will not miss changing out that stator.  I laugh inside when I look at the flywheel puller we have on the shelf and think 'remember when' . . .

[fnichols]

I thought that motor wasn't that old?

2003 and I have no idea what's wrong.  Plan on collecting some donations to get her fixed.

[bluedolphin]

First, I want to thank everyone for their help and suggestions. ben87, I think you hit the nail on the head. The mechanic did start with the carbs - overhauled them. No luck, then he said the stator is fried - $400 later - well, he says one side or the other is not working. It ended up being a switch box that he had to replace. If I had to guess, the stator "PROBABLY" needed replacing, like ben87 said. Someone also said "switchbox" and I told my mechanic to maybe check that. He said carb overhaul is a maintenance issue, anyway, so he did that first. Total bill with labor was $1,087. I was just thinking if he started with the switchbox, maybe I did not have to go replacing the stator. I don't know. The good thing - she's running better than before. Thanks again to everyone.

[GoneFission]

Buy one on eBay and keep it - they are as much as $250 from the dealer:

http://cgi.ebay.com/ebaymotors/Quicksil ... enameZWDVW

See ya on the water!

[jdupree]

If you can't find one try these guys.  Bought power pack for last motor and the price was great.
http://www.outboardignition.com/mandmse ... l=47&val=9