Losing Power - After two hours

[nola mike]

4,200 rpms cruising at 29ish MPH, the boat loses power, and slows ways down to all but a dead stop. It then revs back up and boat starts to go forward again (i haven't touched the throttle) but it won't get anywhere close to 29mph again, maybe 11 tops.

Again, the critical information is are you doing 11 mph at 4200 rpm at that point, or are the rpms increasing, but not back up to 4200 either?

 

[Kconleyk]

Again, the critical information is are you doing 11 mph at 4200 rpm at that point, or are the rpms increasing, but not back up to 4200 either?

When I lose power and come to almost a stop (still not touching throttle) it revs back up to 5,000ish rpms, then settles back at where it was at 4,200. Once it settles back the boat starts going forward again, sometimes 5 mph, sometimes 8 sometimes 11, but never back to the speed I was going. It seems bogged down.

 

[nola mike]

When I lose power and come to almost a stop (still not touching throttle) it revs back up to 5,000ish rpms, then settles back at where it was at 4,200. Once it settles back the boat starts going forward again, sometimes 5 mph, sometimes 8 sometimes 11, but never back to the speed I was going. It seems bogged down.

Ok, that sound like something is slipping then. An outdrive problem (gearshaft, broken gears) wouldn't recover. Rubber related options are coupler and prop hub. Not sure how long a prop can slip before giving up the ghost altogether. A coupler probably wouldn't last long once it starts to slip, esp at high rpm, but I'm not certain of that. The next step is to mark the prop hub and prop. If it acts up, see if the marks are still aligned. The gauge issue wouldn't be related. A video would still be helpful.

 

[Kconleyk]

This happened on one trip and I instantly installed a new prop and hub, and it happened again on the next trip with the new prop and hub. The boat in that first two hours, ran perfectly, and better than ever, gaining cruising speed that I didn't have before.

So I am positive it is not the hub or the prop

 

[nola mike]

This happened on one trip and I instantly installed a new prop and hub, and it happened again on the next trip with the new prop and hub. The boat in that first two hours, ran perfectly, and better than ever, gaining cruising speed that I didn't have before.

So I am positive it is not the hub or the prop

So if you're ACTUALLY at 4k rpm and 10 mph and it isn't the prop, coupler is the only other option. Your gauge issue makes me think you might not be there though. At 4k rpm, the engine should sound like it normally does at 4k rpm.

 

[Kconleyk]

So if you're ACTUALLY at 4k rpm and 10 mph and it isn't the prop, coupler is the only other option. Your gauge issue makes me think you might not be there though. At 4k rpm, the engine should sound like it normally does at 4k rpm.

It is so hard to explain, I will try and get out this weekend and take a video. My daughter has a soccer tournament, so I hope to squeeze in some time. Would a coupler work perfectly for two hours, not missing a beat then all of the sudden stop working, then magically work again the next trip out?

Between her playing soccer and softball, and I am the General manager of Swimming pool construction company, this is a crazy busy time, so a hard time to keep diagnosing a problem that I can't go test I know.

I appreciate the help and will try and post a video soon.

 

[nola mike]

Would a coupler work perfectly for two hours, not missing a beat then all of the sudden stop working, then magically work again the next trip out?

I mean, if the rubber is melting somewhat and then solidifying when it cools back down...I don't know if this actually happens, and I can't imagine it would do it for many cycles

 

[Kconleyk]

I mean, if the rubber is melting somewhat and then solidifying when it cools back down...I don't know if this actually happens, and I can't imagine it would do it for many cycles

That makes sense, there is no easy way to examine the coupler correct? Involves taking the outdrive off?

 

[Stinnett21]

Coupler is where I was heading from the get go but then he said, if I'm understanding him right, the rpms jump to 5000 which is beyond his throttle setting. How could that happen? I'm not a tech but that I find bizarre.

 

[Kconleyk]

Coupler is where I was heading from the get go but then he said, if I'm understanding him right, the rpms jump to 5000 which is beyond his throttle setting. How could that happen? I'm not a tech but that I find bizarre.

I am just a life time IT guy, who now managers construction works, unless I can type it with my hands, I ain't fixing **** or understanding anything with engines haha. So I can only describe what is happening, and for all I know the tach could be reading wrong and just over reacting.

Cruising I am 4,200 rpms on the tach, when this happens the rpms drop real low and I can hear the engine do the same, the engine then revs real loud and the take goes passed 4,200 rpms and then slowly settles back to 4,200. I can hear the engine over rev when this happens. Is it just reving back to 4,200 but the tach flies past it because it happens so quick, then settles back in place, I have no idea just stating what happens

 

[Kconleyk]

Read a few articles and one thing about couples I've read everywhere seems to be a burning rubber smell and an awful noise, and I haven't experienced any of that. I have smelt gas as it was happening but defintely not rubber

 

[ccoon520]

Maybe a fuel supply issue pre pump?

Something like a mostly blocked fuel tank vent and as you go along it slowly reduces the amount of fuel available due to vacuum in the tank until the engine starts to die and allowing for the vent to catch up a bit?

Then if the fuel line is partially collapsed from the vacuum and never able to fully reexpand it could be why you see it intermittently hit the engine after that time period.

 

[Kconleyk]

Maybe a fuel supply issue pre pump?

Something like a mostly blocked fuel tank vent and as you go along it slowly reduces the amount of fuel available due to vacuum in the tank until the engine starts to die and allowing for the vent to catch up a bit?

Then if the fuel line is partially collapsed from the vacuum and never able to fully reexpand it could be why you see it intermittently hit the engine after that time period.

Thanks, I will look into this as well

 

[Kconleyk]

Everyone,

So my daughter has had two out of town soccer tournaments in a row over the weekends and playoffs so just jumping back into a free second to look at the boat. A couple notes below if anyone has any ideas.

1) Bought a new fuel filter/water separator and will post pics tomorrow when I get it changed of what the fuel looks like
2) Bought a new Anti Siphon Valve but can't for the life of me figure out where it is, to change it
3) Everyone mentions the fuel tank vent, which I know where it is on the side of the boat, but outside of looking in the tiny opening I can't see any clogs
4) See the picture with red marking below, I noticed this vent tube is not attached to anything and on other the other side there seems to be a plug in it? See the red circles
5) See the yellow picture below, this cap has a crack in it, what is this?

Lastly, when I opened the motor hatch like 5 wasps flew out, so I am sure there is a nest somewhere I can't find, could that be clogging something up?

 

[ccoon520]

Everyone,

So my daughter has had two out of town soccer tournaments in a row over the weekends and playoffs so just jumping back into a free second to look at the boat. A couple notes below if anyone has any ideas.

1) Bought a new fuel filter/water separator and will post pics tomorrow when I get it changed of what the fuel looks like
2) Bought a new Anti Siphon Valve but can't for the life of me figure out where it is, to change it
3) Everyone mentions the fuel tank vent, which I know where it is on the side of the boat, but outside of looking in the tiny opening I can't see any clogs
4) See the picture with red marking below, I noticed this vent tube is not attached to anything and on other the other side there seems to be a plug in it? See the red circles
5) See the yellow picture below, this cap has a crack in it, what is this?

Lastly, when I opened the motor hatch like 5 wasps flew out, so I am sure there is a nest somewhere I can't find, could that be clogging something up?

I can't help you with # 2 or 3.
#4 the left circle appears to be ducting for your blower. If this is the case then it should be free floating because it picks up fuel vapors from the engine compartment and pushes it out the back of the boat so you aren't sitting on a bomb when starting it. I do not know what the right circle is.

#5 appears to be your bilge pump. If it has a crack you should replace the pump otherwise you'll be in for a bad day when you need it.

 

[tank1949]

Everyone,

This is from another thread because I thought it was a prop issue, but below is my experience on my latest trip out. New boat owner, 1999 Bayliner Trophy, 21' cuddy cabin. Bought it to take my 9 year old daughter out.

First two trips boat ran great, but were short trips. Last trip, boat ran great for two hours but on the way back started losing power and over revving then jumping back to right rpms. Wrote it off to I spun the prop, bought a new prop and took it out yesterday.

So update, bought and replaced the prop, launched today and ultra high tide after storms to make sure i didn't spin a prop from shallow water. First time launching just me and my daughter (9) and she did great helping tie the boat up and hold it while I ran to get truck.

So first two hours boat ran perfect, got on plane quicker than ever, hit higher speeds than previous normally at 28.2 at max was up at 30.9. Crushing speed at 4,200 Rpms at 28.4 mph.

We rode out did some site seeing and rove for about 2 hours. Turned around to hide back, never had the boat turned off, we floated on neautrel for about five minutes while she grabbed us drinks and a snack.

Heading back, same thing as last weekend (last weekend we thought it was a spun prop, but worked perfect for two hours then did this as well), started in got up on plane and the boat kept losing power, then reviving real high then going back to correct Rpms and mph, then drop down and up again. Kept losing Rpms then over revving then holding tight for a few then the same over and over again.

I'm lost, it ran so good with the new prop I thought I had fixed it.

Took us a long time to get back to the ramp.

Fresh gas, new prop, under 2,000 Rpms it seems to run fine, only when you add throttle and only after about two hours of running perfectly.

All gauges show oil temp, battery, etc as good.

Any ideas?

Check fuel filters, including inside fuel pick up tube for crap. Also check fuel vent for obstruction like mid-dobber nest. Been there!!!!!

 

[Eric 3.7LX Alpha 1]

Everyone,

So my daughter has had two out of town soccer tournaments in a row over the weekends and playoffs so just jumping back into a free second to look at the boat. A couple notes below if anyone has any ideas.

1) Bought a new fuel filter/water separator and will post pics tomorrow when I get it changed of what the fuel looks like
2) Bought a new Anti Siphon Valve but can't for the life of me figure out where it is, to change it
3) Everyone mentions the fuel tank vent, which I know where it is on the side of the boat, but outside of looking in the tiny opening I can't see any clogs
4) See the picture with red marking below, I noticed this vent tube is not attached to anything and on other the other side there seems to be a plug in it? See the red circles
5) See the yellow picture below, this cap has a crack in it, what is this?

Lastly, when I opened the motor hatch like 5 wasps flew out, so I am sure there is a nest somewhere I can't find, could that be clogging something up?

2- The anti siphon valve is part of the fuel line leaving the tank.

3- The fuel tank vent could be blocked and could cause an issue. As your engine consumes fuel, the tank empties. Air enters the tank via the vent. When your at the pump filling the tank, the air in the tank has to exit to allow the fuel to enter the tank. You could try disconnecting and blowing thru the hose to see if it is clear or blocked. I have an inline vent whistle on mine. As I fill up the air exiting the vent makes a whistle sound and stops when the tank is full, before being overfilled, and dumping gas out the side of the boat. The lack of a whistle sound would also let me know if the vent was ever blocked.

4- The duct hose with red marking is your bilge blower hose. It should be replaced with new, and you should be using the blower for a few minutes to air out the engine compartment of any fuel vapors before you start the engine after sitting for an extended amount of time. Yours is useless right now and not safe.

 

[Kconleyk]

Tonight I changed the fuel water separator and the anti siphon valve. A few notes below

1). Picture attached of the gas that came out, first pic is the first full cup which has a tiny bit of sediment in it but mostly just gas, the second pic is the bottom of filter very light colored and a lot of sediment in it. Not sure what that means but figured it's worth a mention
2) siphon valve, had some grass/debris in it and was very gunked up, can't really tell from the picture
3) when I was done I added some fuel stabilizer (about half a tank left of new fuel)
4) hooked up ear muffs and it fired right up, smelled gas for a second but that went away
5) wasn't sure if I should leave it in idle or out throttle on it with ear muffs, I tried to add a little throttle and let prop spin, the RPMs didn't move, but the prop was def spinning and would go faster as I gave me throttle, so maybe the tach for Rpms isn't functioning correctly?
6) the trim tach is stuck on all the way up no matter how I have the outboard positioned or trim tabs positioned

Anyway will be Thursday before I can take it out and that will be after work so won't be for crazy long but will try and take a test drive.

Thanks everyone for the feedback and let me know your thoughts

 

[nola mike]

Tonight I changed the fuel water separator and the anti siphon valve. A few notes below

1). Picture attached of the gas that came out, first pic is the first full cup which has a tiny bit of sediment in it but mostly just gas, the second pic is the bottom of filter very light colored and a lot of sediment in it. Not sure what that means but figured it's worth a mention

That first pic looks like you have water in that gas. Did you let it sit to see if it separated?

6) the trim tach is stuck on all the way up no matter how I have the outboard positioned or trim tabs positioned

Yeah, your sender is probably bad. That comes after "is all my teak oiled?" In priorities for fixing on my boat.
Would still like a vid, since if your engine is slipping we're still chasing the wrong problem

 

[Paintman1960]

That comes after "is all my teak oiled?" .

Too funny !!