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50HP lack of power

FloridaFloater

New member
I'm a noob to the forum, so I apologize for my ignorance in advance. But I have a 20' Pontoon with a 2004 50HP BF50A. I purchased it approx 2 years ago and noticed it was surging and then showing a lack of power, I figured it was bad gas from the seller.

What exactly is happening is: It doesn't matter how many people are on the boat (only myself or the family so weight isn't a major factor) it starts fine, runs and sounds great, but will top out full throttle at 16 MPH, I can pull the throttle back to 3/4 throttle and it will surge forward with power and increase speed dramatically but only for a few seconds, then falls right back down to approx 16 MPH. It will do this time after time over and over again. The engine never stalls or has any other issues, just lack of power, surges and back to lack of power

I first cleared the fuel cell out, changed the prop to a prop to max out the top speed for the engine, end result was still the same. I had a mobile mechanic come by the house (friend of a friend to save a ton of money), he figured it was the carbs needing cleaned. He took all three carbs, micro-scoped, cleaned and reinstalled said he synced them back to factory zero then turned back up, the engine still was not performing properly while on the muffs so he though it was the fuel pump not putting out enough fuel. We changed out the pump with a new one, he tried to get it going but for some reason the engine would not run consistently. After he left I continued to tinker with it and was able to get it running proper on the muffs (starting on the first turn within a few seconds of turning the key.). Took it out for a water test under load... Ran just the same as before and STILL THE SAME ISSUE!!

This is shorted version of about 3 months of working with it but I can not seam to figure out what the true issue is. I have moderate tech skills and usually work on all of my own stuff, but since I couldn't seem to figure it out I went outside to the mobile mechanic. Has anyone had the same issue or know what the problem is? Thoughts of where I should check?

Thanks in advance!
 
Sounds like fuel starvation or air getting into the fuel system. is the fuel bulb full/ hard once under load maybe someone can try to pump it to see if you can come up in power? Is the bulb sitting upright this helps hold the non return balls in place. Have you changed out the fuel line or fittings as it may have a minute hole sucking air in once you load the engine. Have you also checked all fuel filters including the one in your tank?
I would start with buying a new fuel hose and maybe trying to run her off a small portable tank as a low cost fault finding routine this way you rule out or confirm if your problem is before or in the motor. If this feels like its working you will need to go for a sail to load the motor properly to make sure.
Try these things out then we know where to move on to. If this is not of help then we move on to your float chambers and or filters but one step at a time ruling out the easy stuff first is the best approach.
Good luck.
 
I forgot to put in my first post that we had replace the old fuel filter that is in the cavity of the outboard as well as installed a fuel water seperater. I'll definitely take the advice and replace the fuel hose/primer pump first as well as trying on a portable tank. I'm not sure it will be this weekend but maybe Wednesday but I will def try soon and update as I go.
 
Troubleshooting 101!! compression test first, There has been no mention of spark test anywhere even though it does sound like a fuel delivery issue.
 
While I have was about to do a compression test on it, the screw in insert for my gauge system was larger than the spark plug hole, so I was unable to do a compression test, however I have to believe all 3 have spark due to all three plugs looking identical with soot. (Yes I replaced the plugs).
 

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Engine is running rich! Too much fuel or insufficient spark, Have you tried the joe reeves home made spark tester? Spark plug can be cleaned.
 
Engine is running rich! Too much fuel or insufficient spark, Have you tried the joe reeves home made spark tester? Spark plug can be cleaned.

I have thought that it is acting like its bogging down with too much fuel, but like I said I'm a noob at small engines. I found this online when looking up the home made spark tester, from what I read its easy and straight forward so I will try it as soon as it stops storming (It has been storming here off and on for 3 days now.). But check out the link and let me know if you think this would work:

http://www.boatingmag.com/boats/build-your-own-outboard-spark-tester
 
Ok so I tried to create one of the spark test that I listed above. Weirdly enough nothing happened but the engine still started... I tried on all three wires same accurance, nothing sparked but the engine started. I did read that the EFI engines would not allow it to work due to something about frequency, but all in all it just might be my crappy engineering that caused it to not work.

however, I did find it interesting that with rotating wires on and off that the engine would start up and run(first key turn each try) with only two plug wires in place. So back to square one??? Fuel maybe?? Lol
 
Here are some basic questions, that you may not have an answer to....but should before you go too far into this....

1. When full throttle.....what are the max rpms that you are running (not speed....rpms)? Without a tachometer, you are pretty guessing at things.

2. What size prop are you using? It should probably be somewhere between an 8 to a 10 pitch for that size pontoon.

3. Is the engine coming to temperature? If the engine is running cold, it will run rich. Thermostat fully opens at 162 deg F.

4. Is the motor trimmed almost all the way down? Or mounted too high....or too low. If trimmed up too high, it may be cavitating. Could also have the same result with people sitting at the bow of the boat, which can cause the motor to raise out of the water too far.

5. Are the timing marks lined up properly? The T on the cam should align with the T on the powerhead....while the line with the T on the flywheel aligns with its corresponding mark on the powerhead..

By the way, you do not have an EFI engine, so you may want to relook at your engineering of the spark tester.

If you or a friend have a timing light, you could put it on each plug wire and get your engine to misbehave...watch what the light does...goes out, blinks intermittantly, etc.
Then move it to each plug wire, one at a time, and do the same test. If the light is consistant on all the plug wires, then you can probably put the questions of spark to the side.

Mike
 
Here are some basic questions, that you may not have an answer to....but should before you go too far into this....

1. When full throttle.....what are the max rpms that you are running (not speed....rpms)? Without a tachometer, you are pretty guessing at things.

2. What size prop are you using? It should probably be somewhere between an 8 to a 10 pitch for that size pontoon.

3. Is the engine coming to temperature? If the engine is running cold, it will run rich. Thermostat fully opens at 162 deg F.

4. Is the motor trimmed almost all the way down? Or mounted too high....or too low. If trimmed up too high, it may be cavitating. Could also have the same result with people sitting at the bow of the boat, which can cause the motor to raise out of the water too far.

5. Are the timing marks lined up properly? The T on the cam should align with the T on the powerhead....while the line with the T on the flywheel aligns with its corresponding mark on the powerhead..

By the way, you do not have an EFI engine, so you may want to relook at your engineering of the spark tester.

If you or a friend have a timing light, you could put it on each plug wire and get your engine to misbehave...watch what the light does...goes out, blinks intermittantly, etc.
Then move it to each plug wire, one at a time, and do the same test. If the light is consistant on all the plug wires, then you can probably put the questions of spark to the side.

Mike

to answer your questions (what I can at least) I will go by your numbering:

1. My tachometer is not connected unfortunately. This is another item I asked my mobile tech to do for me that he never did. It has never been connected with this engine from what the previous owner had told me when I purchased it a couple of years ago. I had a Mercury engine on it when he bought it, but installed this Honda later on. So unfortunately I don't know the RPMs, but I do not believe the engine is truely maxed out.

2. It is a Hustler 12 1/2 X 8 H1-1208

3. I can attest that there are some times when the engine could be cold, but most of the time I am running the engine for between 30 mins to an hour while cruising to our swimming spot. So I want to believe that is 90 degree weather that it gets up to temp during that time.

4. When I first purchased the boat it was cavitating due to the previous owner having a Mercury prop on it, after installing the new prop I saw an immediate difference in power, it is no longer cavitating but still lack of power. When full throttle and going back to look at where the engine is sitting in regards to the water table, it sits at the correct height. Also there are rarely more than 2 adults and 2 kids on at any given time. They tend to stay near the back while in travel.

5. I will look at the timing marks as soon as I can, unfortunately I haven't looked at it yet.

i thought I had an EFI (something I ready about the emissions) I will have to go back and look at the spark tester again. I soldered a wire on the threads of a spark plug that was connected to a clip, put the clip on a bolt that the engine uses as a ground bolt connected the spark plug to each of the wires and did not see fire from any of them. So I will have to re-evaluate.

it it would be very difficult to attempt to do the timing light while the engine misbehaves due to it only doing it while it is under load on water, on the muffs it acts fine.


Thank you you for the thought provoking areas, I will have to look into it all again.
 
If you do not find an issue with other things, I strongly suggest figuring some way out to use the timing light while underway.

You might have to figure out how to lay and keep the light in place on the back deck. At least tie a line on it....so you do not lose it overboard. You have to run the test without the hood. Having a second person drive, while you watch the light is helpful. You have to stop and hang over the deck and move the connection to another spark plug wire. You just have to be very careful.

We do this a lot. It generally is very good at telling us if the problem is electrical or something else. That lets you focus on something else...like fuel....exhaust leaks, etc.

As far as the spark test. If you can pull the spark plug wires off one at a time while the engine is running on a hose and the engine rpms go down each time, then you have spark at all cylinders. It just does not tell you if it is going to change once under load.

Mike
 
One thing I forgot...

If the thermostat is stuck open, the engine will not come up to operating temperature, even in 90 degree weather. The thermostat keeps the engine temperature where it should be for best combustion of fuel.

If you do not measure it, you do not know for sure.

Mike
 
One thing I forgot...

If the thermostat is stuck open, the engine will not come up to operating temperature, even in 90 degree weather. The thermostat keeps the engine temperature where it should be for best combustion of fuel.

If you do not measure it, you do not know for sure.

Mike


Ok cool. Would you test it the same way you test an automotive thermostat? If so, I will have to locate it, remove and test, then can leave information. Thanks
 
I am not sure how an automotive thermostat is tested....I do not work on cars.

Honda says to suspend the thermostat in water on a stove and watch the temperature of the water as it opens.

I do not think you have to go to that extent. It is pretty obvious if the Honda thermostat is stuck open...just by looking at it.

It probably would do no harm to do the test, just to make sure it is not just partially opening.

Mike
 
I am not sure how an automotive thermostat is tested....I do not work on cars.

Honda says to suspend the thermostat in water on a stove and watch the temperature of the water as it opens.

I do not think you have to go to that extent. It is pretty obvious if the Honda thermostat is stuck open...just by looking at it.

It probably would do no harm to do the test, just to make sure it is not just partially opening.

Mike

it is the same way to test an automotive one. I will be taking a look at it as soon as I can due to the storms in the area, but I will def do the test as soon as I can.
 
yes it is ,just suspend it in middle of pot,not on bottom of pot,should open fully at or close to 162deg F. When u pull thermostat see if it is slightly open already,they do not open much.less than a 1/4inch.
 
So yesterday a buddy and I took the pontoon out in between storms. I used an inductive timing light on the spark plug wires while fully under load going a total of 13 mph, all three wires are sending fire at approximately the same rate (from what I could tell). All three had approx the same strobe effect on the light. I went ahead and tried an alternative fuel source. I connected an auxiliary tank and ran full throttle for about 15 mins to clear the line and get the new gas in. There was no change. Max speed on this trip was 14.79 Mph and was doing the same thing, when slowly pulling back the throttle to approx 3/4 throttle it would jump up in speed for a moment then bogg right back down. My buddy wanted to see what would happen when doing a U turn while under load, it made the end bogg down even worse, he said his two cents was the fuel air mixture. But any. Suggestions at this point of where to move next? BTW I haven't had a moment to test the thermostat out yet, but I can tell you while letting the engine run on the muffs after being in salt water, the water spraying out is nice and hot.
 
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