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New 250 hp issue

C

Cmerc

Contributing Member
Recently repowered with trip 250s they now have just under 40 hours and they have been great till now.
I have been playing with props and finally got a chance to try new Mirage plus 14 3/4 x 21.
Outer engines turned 5900, & 6000, center hit 6200.
Heres the issue, at 5200 and above it runs great, under 5000 the rpms oscillate. cruise at 4800 and the revs will drop off to 4400, then back up to 4800 this oscillation takes between 5 and 10 seconds and happens at any rpm range under 5200.
the engine starts with no issues, and idles fine with no oscillation.
tomorrow I am gonna change the main fuel filter and check the fuel line and clamps.
I have a 3 year warrenty, and my dealers mechanic is gonna come and chexk it out next week, but just wondered if anyone had any thoughts, oh and there are no fault codes.
 
Can't help but I'm watching with interest as my 225 is doing similar but at <2500 rpm, above that it's fine (also seems to go away once the engine is up to temperature).
Hope it's just a fuel filter.
 
Don't now anything about the new 250's, but The fuel feed system on the 250 appears to be almost identical to the one on the 225 and 200, based on the parts diagrams on www.boats.net.

Is this happening on all three engines???? If so, then look at your fuel tank(s) and fuel lines to the engines. It could be anything from a clogged vent tube, a clogged pick up tube in the tank, a malfunctioning check valve in the pump up bulb, to a clogged F/W separator, assuming you have those, which you should.

If it's just the center engine, then on the 225, the first culprit is often the HP fuel filter. Those filters have been the source of many performance problems on the 225. However, there are other filters and screens that can get clogged or dirty, including one on the fuel rail itself. See item 4 at:
http://www.boats.net/parts/search/H...Later/BF250A XA/FUEL PIPE INJECTOR/parts.html

See especially items 8 & 9 at:
http://www.boats.net/parts/search/Honda/Outboard Engine/2007 and Later/BF250A XA/PIPING/parts.html


Also, on the 225 there is an intake air bypass (IAB) solenoid that kicks in at 3950 RPM. This solenoid opens vacuum to a vacuum diaphragm attached to your intake manifold, which in turn operates a set of baffles in the intake. These baffles allow more air to get into the cylinders and makes the engine run more efficiently at high rpm's. When those baffles don't open up properly it can cause changes in rpm's at high speed. Also, if that vacuum line is disconnected or leaking it will also cause the problems you are experiencing.

See items 5, 24, & 10 in the following...
http://www.boats.net/parts/search/H...nd Later/BF250A XA/INTAKE MANIFOLD/parts.html

If you or anyone else reading this is interested in a more detailed description and testing procedure of the IAB, send me an e-mail at [email protected].
 
CHawk, very detailed and thoughtfull, as is usual for you, thanks.
it is only the center engine having the issue, I just changes the main fuel fuel filter, didnt figure that was the issue, and it wasn't, I also checked the clamps on the fuel line, both the tank and fuel filter end all are tight.
Aftre I changed the fuel filter I ran it at the dock in Neutral at 2000 rpm same issue, but only about a 200 rpm oscillation.

One more bit of infomation i forgot to add, when I first went out to test the props,
I aomehow forgot to put the center engine in gear, and may have hit the rev limiter for a second at most before I realized, but I cant see that causing a problem.

As I said, the engine only has 37 hours so I am gonna leave it alone till the dealers guy comes and checks it next week, but like you, I am leaning to one of the engines filters, although I am somewhat surprised that there is not an issue at WOT, or above 5200 for that matter.
 
I agree to let the dealer work it out under the warranty. I doubt if hitting the rev limiter is causing the problem, but you never know.

Do I understand correctly that you didn't have this problem before fooling with the props? If it started with the new props, I'm wondering if you are having some sort of cavitation around the props when they are cranked up. Is the problem there when the outside engines are in neutral? You might want to test that before the tech shows up.
 
Props, heres the story.
the dealer had to order props(3) two standard one counter rotation, when they gave them to me I did not look at the boxes and ended up with two counter and one standard rotation, so we put one on the starboard and one on the port, every thing was fine.
The dealer got the correct prop for the center engine and I installed it, thats hen this issue started, there is no cavitation, or vibration and as i said if I trim the engines up I get 6200 6250 on the center engine.
As to hitting the rev limiter, I dont think that is an issue at all, when she was first rigged they used my old props which were 4 blade 17 pitch, and she was hitting the rev limiter, same thing when I tried 19 pitch props, so hitting the limiter in netural would be no different than hitting it in gear, except therenwould be less load on the engine.
Finally I teied itatthe dock in netural with only the center engine running, and as I said there was fluctuation at 2000 rpm.
I qm leaning to a fuel issue in the mid range rpm, fuel filter, fuel pump, I will report when they solve it. This is the only issue I have had with these engines, They have been great, and interestingly my top end has incresased by over 6 mph, and mpg by 0.2 mpg to just a shade over 1.2 mpg.
 
OK. Guess that eliminates a cavitation problem. I think many will be interested in what they find. Standing by.

Metal-Chicken. As a general practice, you want to let those engines warm up before casting off. I think many have the hesitation issues when cold. Mine does. I suspect it has something to do with getting the VST warmed up, but that's just a guess.
 
So according to my wife, I must have done something wrong when I changed the prop, or its defective! Grrrrrrrr
 
This shouldn't happen with new props, but pull the prop on the center engine and inspect the area in the hub where the rubber is connected to the metal on both the outside and inside. If the rubber is raised a bit along either seam, you've got a "spun" prop. Normally, they will initially slip at high rpm's. But I've had them also initially only slip at intermediate rpm's in the past. The old Volvo out drives were notorious for that.
 
No resolution yet, but its looking like dirty HP filter, unfortunatly the dealer is out of stock, they may try and clean it as a temp fix till they get new ones in. Am I correct in assuming that there is the equivalent of a fuel bowl, similar to a carb setup, that fills with fuel and the engine is supplied from it?
If so, then it make sense to me that the filter was restricting the "fuel bowl" from filling fast enough to supply the engines needs at mid range, but the HP pump was strong enough to over come the dirty filter at WOT.

one thing is sure, the dirt did not come from my fuel tank, I just cut open the before engine fuel filter to inspect it, and its cleam as a whistle.

will post the final solution when we get it.
 
I don't know how much the design has changed for your new engines, but I have an HP and LP fuel filter on my 2006 225's. I assume yours is the same. The HP and LP filters are paper cartridge type. Just change them both and clean out the water vapor fuel strainer. I order all my parts here if interested.

My engines also have inline water separator / filters just after the priming bulbs. I will say after this years maintenance, I did not find any dirt or accumulation in the HP and was impressed to see how clean everything was and the effectiveness of the filters.

http://www.boats.net/parts/search/Honda/Outboard Engine/parts.html
 
Update.
just spoke with the mechanic, he tried to open the VST unit to check/clean it, some of the screws are frozen so they have orderd a new VST unit, hopefully they will have it next week.
 
Those screws CAN be removed, it just takes some patience with PB Blaster and a good impact driver. Once removed, replace with new off-the-shelf SS screws.
 
He got most of them out, but did not want to take the chance of disabling the boat since the new one was already on order, and it is a warranty issue, also I did not want to leave the boat at his shop dock till the part comes.
Apparently the filter was dirty as I said, but also had some particles in it as well, as I said it did not come from my tank as I cut open the filter I took off, and it was spotless.
I believe that engine sat at the dealer for at least six months, wonder if There was old fuel, or some other liquid in the system when it came from Honda?
I would expect that they run it after assembly, if so perhaps they did not pickel it.
 
I replaced the screws in my VST top with allen head SS screws. Turned out to be a good move. I don't think you can get that done under warranty but you could at least get them to coat the threads of the existing screws with NeverSeize while they have the VST out. If you keep the engines past their warranty period you'll be glad you did.
 
Good Idea, although I doubt I will keep the boat past warranty(3 years) planning to move to Abaco next year, and I hve a 23 Albury over there, this boat is just too much boat for over there so I will sell it engines are 6 months old and only about 35 hours.
 
Lol you think you are waiting with interest, my kids are coming in six days and we have an Exuma trip planned.

It is looking like a dirt issue with the VST, they cleaned the HS filter as a temporary measure while they are waiting for a new VST unit and filters, should be here this week.
I have not used the boat since thwy returned it to my house last week, but near as I can tell, she ran ok on the way back to my house.

Hopefully it will be resolved this week.
 
No resolution yet, but heres an update, all be it that it only adds to the mystery.
the new VST and Filter arrived, but I have asked the mechanic to leave it for two weeks untill my kids and grand kids who arrive on Saturday leave.

Today I changed the prop from the 21" back to the 19" pitch, took the boat out and believe it or not it was much better, the rpm oscillation is between 100 a 150 rpms.
an intresting side issue came up, every time I pressed the trip/ tilt switch, the digital rpm gauge disappeared for a few seconds strangely the engine temp which is a part of the display was not affected, and the Analog tach was fine.
it happened at speed, at idle and in neutral, strange huh.
Heres my theory, and the reason that I decided to try the smaller prop, the issue IS fuel and load related probibly due to the dirty VST, and the smaller prop does noload" the engine as much and create a fuel issue.

What about you guys, what are your thoughts, BTW they did clean the HS filter so that could have helped too.
 
On my boat the battery gauge takes a hit from 13v down to 11v when I use the tilt/trim due to the load.
Maybe your battery is in not so good condition?
 
Check this out!
we are planing to go to Exuma on Thursday, full load of fuel (400 gallons), 5 adults and 2 kids plus supplies, so I decided to swap props and replaced my 21's with my 19's, went out today to the beach, the boat ran like a charm no rpm oscillations.
 
Good news!
My money is on it being the new HP fuel filter that actually did the trick as i just can't see how changing the props could make an engine surge.
 
Absolutly not the props, except IMHO I think trying to spin the 21's is causing the engine to work harder and the dirty filter is not allowing enough fuel flow.
BTW, the HP filter was cleaned, as they were out of stock of new ones.
gonna change all the filters and VST when my kids leave i. 2 weeks.
 
So heres the update after the Exuma trip.


First off, the weather forecast was wayyy off instead of the predicted 2 ft seas and 12 knots, we had 4+ at 3-4 seconds and 20+ knots, not fun at all, broke a few things on the boat, fortunately nothing critical, or important, but the best speed we could make was 17 mph, it was brutal.
Once we got there it was fine as the Exuma cays run roughly NW to SE, and most things you want to do are on the west side of the chain.
The engines performed flawlessly, not a moments trouble, the center engine never oscillated a bit in RPM at any throttle setting, going to Exuma we only got .9 mpg which was disappointing, gut with 400 gallons of fuel, 60 water and 20 diesel, plus 5 adults and 2 kids plus gear I kinda expected that.
One thing that I did find surprising and pleasing was in 2 ft seas, fuel economy went up to 1mph, some times 1.1 mpg at any speeds between 32 and 40 mph.
We covered 220 miles and a shade over 230 gallons of fuel, we spent two nights at Ship Channel Cay at the "Power Boat Adventures" site it is a bit rustic, but in a great way, and everyone agreed they would love to go back again, especially if we went as couples instead of a group of 7 people.
The owner, Capt Nigel and the staff there are awesome, and the tourists that come daily from Nassau seemed to love the shark and stingray feeding show.
There was one moment of concern when both bilge pumps came on, and stayed on, after sone investigation I found a hose clamp on the generator salt water side had busted and pushed the hose of, but it was a quick fix and I sprayed the unit down with fresh water and WD40 and it ran fine until we got back home to Nassau, hopefully there will be no long term issues.
 
Sounds like a great trip. Glad everything worked well. Good for ya.

One lesson learned from that trip is it's a good idea to install an alarm connected to a separate float switch in the bilge. I personally know of several sinkings when the captain and crew were unaware that the bilge pumps were running until it was too late. One was a 34 ft. Grady White off the Diamond Shoals. Boat was a total loss. Fortunately, a CG tender was not too far away and executed the rescue.

Yes, you can never trust a NOAA forecast for offshore. Don't bother to ask how I know that. 4+ foot waves with a very short period like that is never fun. Also, been there, done that - in a much smaller boat.
 
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