WOT Fuel Burn Difference BF200's

My 200's are on a cat as well and I have the same issue. I feel that they should be higher but there is nothing I can do about the height. I have raised them up to get the cavitation plates up to the surface but I can hear them cavitate sometimes, so may drop them back down a hole. I trim the engines up when I am drifting and I slow one down at a time when stopping to keep the water from rushing up the back of them.
I never noticed any fuel burn improvement after changing the 02 sensors. I suppose it could be possible the sensors went bad after one trip, but I hope that is not the case for what they cost. Are you running the updated sensors or the old style? My engines are '03's so they had the old ones.

As for the procedure you used to decarb, that sounds fine. I would still pull the VST's and HP filters to clean and check just in case gunk got in there from he decarb. But at this point I'm also stumped.

Have you done a precise compression test on each of the engines to eliminate the possibility of a burnt valve?

I assume the engine idle is at 650 rpm's or very close to that. At what RPM's do they smooth out while boat is in neutral?

I checked the compression cold before the decarb and warm after. I thought I posted the #'s. I have not done a leak down test as I need to purchase the gauge. I did find that the exhaust valves were tight on the stbd engine so I am going to assume the port are as well. I plan to pull it apart and check that one too.
I am idling, on the flusher, at around 850 on the port and 800 on the stbd. If I bump the idle lever up to around 1k, they seem to want to choke for a split second. They don't smooth out at 1k, they seem to surge a little bit. It seems they are a little better in the water, so the back pressure may be helping that.

Hmmm - The idle speed for the 200 and 225 is supposed to be 650 rpm's (+/- 25) when engines are at operating temperature. That is controlled by the ECM. The surging when engines are cold is normal, but you should have a smooth increase in rpm's when you bump up the throttle. If I experienced what you just described on an auto engine (i.e. the hesitation when adding throttle) I'd be looking for a vacuum leak somewhere. A vacuum leak would also explain the rough idle.

650 in gear in the water, or 650 at idle on the hose in the driveway? The surging occurs even after the engines have run for a bit on the flusher. When I increase the throttle from idle, there is a slight dead zone when I move the lever, then it jumps up. When throttling up in the water, the controls seem very touchy and if you are not careful, you will throw the passengers off balance. I can do it slowly and evenly, but there is a jump from idle to 1k or so. I just figured that was the way the engines were. Once I get past that spot between 850 and about 1k, then the throttle is smooth and even.
I could see a vacuum leak being a problem, but would both engines have the same leak? The idle was good on the stbd engine and just a little bit rougher on the port prior to the decarb, now they are both rougher. I can't figure out what the decarb could have done to make the idle rough.

650 rpm warm at idle in neutral. My 225 bumps up to about 700 to 750 in gear at idle. The flusher NEVER gets you to the correct operating temperature. Make yourself a test barrel if you are going to test the engine properly out of the water.

Did you ever pull and clean the VST's, fuel screen, and HP filter after decarb? If not, that would seem the thing to do before proceeding to other things.

I can clean the vst's. I know you are thinking that may help the idle issue now, but do you think it would have anything to do with the big fuel burn difference between the engines?

When I pull the vst's apart, can I reuse the seals that are there, or do I need to order new ones? I do have a couple extra o-rings for the hp filters, although the seals in there are new now.

You are probably OK reusing the VST seals. On the HP filter, check the O ring carefully. If it looks new, it's probably OK to reuse it too. I doubt it fixing the rough idle problems on both engines will fix the difference in fuel burn. One thing at a time.

The fuel burn issue may be due to the extra energy required for the counter-rotation. That is something beyond my knowledge and should be researched in detail with some more knowledgeable folks.

I can see the counter having a little less economy, but not 2gph at cruise and 6gph at wot. I have swapped the gear cases before and did not recall the fuel burn issues following the gear case, but I may try it again just to confirm.

Obviously you are dealing with two very likely separate issues - the rough idling and the difference in fuel burn.

I went back and re-read your original post and the follow ups. Interestingly, my 225 (same as the 200 except that the 225 has variable timing, which improves top end efficiency) and noted your fuel burn. On my 225, I'm burning right at 20 GPH at 5800 rpm pushing a 6,000 lb fully loaded boat. This is based on the internal ECM that feeds my Honda digital gauges. It seems to be very accurate since my fill-ups are always within +/- 2.5 gallons on a 100 gallon fill-up. The point I'm making is that neither your port engine nor your starboard engine are that far off from the norm, it's just that the difference is bothering you. I still believe that could be due to the counter-rotation issue with your port engine. My advice is to set this problem aside until you solve the rough idling problem.

Your second issue, the rough idling, is entirely different. I noted that you said that you checked the valve clearances on the starboard engine, but I did not see anything about checking clearances on the port engine. Have you done that?

If I were in your shoes, I would reboot and start over.

First, re-check to see if their are any codes on either engine.

Secondly, since the problem seems to be with both engines, I would check the fuel lines from the tank to the engines for air leaks. This is easy to do by fitting a clear plastic hose between the onboard fuel/water separator and the LP fuel filter and look for any air bubbles for each engine. A typical culprit are the fittings on your external fuel/water separator.

Third, recheck compression and do a leak-down test.

Fourth, remove and clean VST and carefully check float and float valve. Check HP fuel filter and make sure there are no leaks in the HP fuel system.

If you have the Helm Shop Manual, then go to the trouble shooting section for "engine does not run smoothly" starting on page 2-15, and methodically go through that.

Ep4 said:

I checked the compression cold before the decarb and warm after. I thought I posted the #'s. I have not done a leak down test as I need to purchase the gauge. I did find that the exhaust valves were tight on the stbd engine so I am going to assume the port are as well. I plan to pull it apart and check that one too.
I am idling, on the flusher, at around 850 on the port and 800 on the stbd. If I bump the idle lever up to around 1k, they seem to want to choke for a split second. They don't smooth out at 1k, they seem to surge a little bit. It seems they are a little better in the water, so the back pressure may be helping that.

Click to expand...

FYI: I bought a leak down tester at harborfreight for $35

I don't have the helm manual. The idle issue has only arisen since the decarb, so I don't think it would have anything to do with my separator or fuel lines. I do plan to check/clean the vst and hp filters. I did not have a chance to tear down the port engine yet to adjust the valves but I expect them to be about the same as the stbd, which I already did.
As far as the fuel burn. I don't recall the difference moving to the stbd when I swapped the gear cases previously, but I can check that again. The 225 will burn more fuel at wot than the 200 because of the variable timing, but will be more efficient at lower speeds, from what I have read and been told.
On similar boats to mine with the same or more hp, the fuel burn seems to be more for me, for some reason. I do believe the engines should be closer in fuel consumption, not to mention the port engine turns 500 less rpms with the same props. I think it should be realistic to attain near 2mpg cruise on a 27' cat with the pair of 200's I have.
My plan is to work on the idle and continue to search for the reason the fuel burn is so different. Any additional suggestions are appreciated.

OK. Keep us posted. This is a really interesting issue and I'm sure other folks may benefit from whatever is found.

I was thinking about your 20gph fuel burn #'s on a 6k lb boat with a single 225 sounds right, but I am pushing a 7500lb boat with a pair of 200's so the fuel burn per engine should be better than pushing a decent load with a single engine. I would not expect twins to burn the same as a single x2.
If we aren't fishing this weekend, I will work on the boat. It's been raining every afternoon lately, so no way to work on it during the week, and the I have to try and fish when the weather and seas are good during the season.

I went ahead and adjusted the valves on the port engine yesterday. They were the same as the stbd, all about .008-.009, so I adjusted the exhaust to .12
I pulled the vst and it was clean inside, the hp filter was good, no sediment or water anywhere and the float & needle were clean and functioning. The screws did not want to come out and I had to use an impact driver, pb blaster and a small pair of vise grips on them. That sent me to Ace Hardware for some new screws, but I did get it back together. Just have to put the intake back on and fire it up. I have never seen anything but clean fuel from the drain tube on either vst, so I may not mess with the other one, unless there is some improvement in the running on the port engine.
I bought a leak down tester and plan to do some checking today.

Got the port engine back together and it seems to be running well on the flusher. I adjusted the cables again and checked everything over, so hopefully it's good now. I won't know if the fuel burn is any better until the weekend. Tried to use the harbor freight leak down tester, but the first one wasn't working right, so I swapped it out. The second one did not seem to hold the 0 setting either, so who knows how accurate it is. It looked like I was seeing around 30%. I could not hear any leaks in the intake or exhaust, but I could hear some leaking in the spark plug hole. When I covered the plug tube with a rag and I could not hear the leaking anymore. I checked the port engine with the intake off so I could listen at the tubes.
Pulle the vst from the stbd engine and it was clean, but I went through it anyway. It's ready to go back on tomorrow.

I took the vst apart on the stbd engine and cleaned it out. It was clean and it did not look to have anything inside but clean fuel. I put it all back together and it may run slightly better, but not as smooth as the port engine. I am not sure what else I can do at this point. I plan to run the boat this weekend.
Checked the MIL again and the stbd had a fast flash followed by a longer flash, maybe 2 sec long. It just repeated this sequence. I checked the port and it had one long flash after another, and that was it. I cleared them both. I did turn the ignition on while I had the intake off and sensors unplugged, to allow the fuel pump to prime after manually priming the vst's, to check for leaks. I did get some steady beeping when the ignitions were on, but figured it was because the sensors were unhooked.

According to the shop manual a long blink followed by a short blink does not make sense. There is no "11" code. A "21" code applies only to the 225 VTEC solenoid valve. A single short flash is a code "1" which is a disconnected or bad HO2 sensor OR a misfiring spark plug.

Recheck again after you run the boat. Clear the codes first.

As far as the fuel burn. I don't recall the difference moving to the stbd when I swapped the gear cases previously, but I can check that again. The 225 will burn more fuel at wot than the 200 because of the variable timing, but will be more efficient at lower speeds, from what I have read and been told.

Click to expand...

On similar boats to mine with the same or more hp, the fuel burn seems to be more for me, for some reason. I do believe the engines should be closer in fuel consumption, not to mention the port engine turns 500 less rpms with the same props. I think it should be realistic to attain near 2mpg cruise on a 27' cat with the pair of 200's I have.

Our cat is 30ft with a pair of BF175s. We recently changed the props due to low WOT RPM's at 5200 - 5300. We went slightly up in diameter and down in pitch. New WOT RPM's are now ~5800. What was really interesting in that the fuel burn went from 70lph @ 20 knots to a new cruise of 50lph @ 19 knots. So that makes a shift from 1.26mpg to 1.64mpg. A huge improvement and much more than we expected. Seems that the rig really benefited from the extra blade area and the deloading of the engines. This hull design is not super efficient, but the boat is vary spacious for it's size so I guess that comes with a price. If your rig is slightly smaller, with maybe slightly better hull design, but weights are not much different, then I guess a target of 2mpg should be around the top end of your expectations. I don't know if you have experimented much with the mpg at different speeds, but we found with the previous props that there was quite a significant gain from dropping the cruise rpms back to around 3400 - 3600 vs a 'normal' 4000. With the new props this change in mpg is not as large, but does still exist.

As for the counter rotater using more fuel, this is only just noticeable on our boat and I don't think that the different fuel numbers you are seeing are coming purely from the different gearbox based on our experience.

Click to expand...

Click to expand...

I believe the lights flashing were caused by turning the ignition to the on position while some of the sensors were disconnected. I cleared the codes and will check again after this weekend's trip.
I was thinking switching to a larger diameter and lower pitch might help me reach a better cruise. One engine will turn 6k now and the other 5500. I am running 14 1/4 x 17's now and was thinking something in the 15x15 range may be good for me. I figured I could cup them and go up in pitch a little if needed. The other option is a 4 blade, but a 17 might be too much and I have not heard good things about the 15's.
Some of the other people I have spoken to with very similar boats seem to be getting 2mpg at cruise, so it does not look to be impossible to get mine closer to that. If I could get a solid 1.5 +, I would be pretty happy with that.

Ran the boat 100 miles on Saturday. Engines seemed to run well. The fuel burn was still around 2gph difference at cruise, which was about 4k. I had no issues all day, until I fired the engines up to come back in. We had been sitting for a little bit before starting. After a minute or so of running, the stbd engine sounded an alarm. It was a steady series of beeps, but not too long, maybe 2 seconds each, one after another. I had this happen once last time out as well. I believe this is the 02 sensor warning. I will pull the codes off each engine to see what the mil says.
I used the flush port to clean the engines, so I have not run them on the flusher since the trip, to see how they sound now. There seemed to be a fair amount of black stuff on the back of the covers coming from the exhaust ports. I get that regularly, but it was heavier this time. I just figured it was due to the longer run, and the fact that I just adjusted the valves and cleaned the vst's.

Counter rotation consums little more fuel. This is normal. Let me have your serial # .if you dont mind
let me run your number, i can let you know what honda dealer can update ur motor. If there is any update available regarding to o2 sensor issues or ecm update. Well i have 225 on mine. I dont have speedo and fuel flow guage on mine.
i used to pay 10 $ a gallon. Now. I pay 4 (long beach .ca) .i m in heaven..

I know I have the old style o2 sensors in both engines and the exhaust tubes are the old style as well. I don't have an issue with changing the exhaust tubes if it will make a big difference, but I was under the impression it will be very costly to change to the new style o2's and the updated computers to go with them.
Not sure I understand the $10/gal to 4$ comment. Is that from the change from what you had to the 225 Honda? Mine eat up some fuel, so I can't say I was blown away by my 200's. My old 2 stroke Merc averaged 3mpg at cruise where I seem to average about 1.3 with the pair of BF200's I have now. I do like how quiet they are and they have plenty of power. I have dumped a bunch of money into them already since I got them, and it seems there is plenty more to invest.

IMO, if you have the time and skill to replace the exhaust pipes with the new ones, I would do that. Honda sells a kit to do the whole process. I does not require that you upgrade the HO2 sensor or the ECM.

Is there any guarantee that replacing the pipes will stop the 02 sensor issues? I just replaced the pair of them and now I am getting a warning the stbd is likely bad already. The old ones tested bad but did not throw codes or alarms. They are not cheap, so I would prefer not to keep replacing them if there is a way to avoid it.

I looked up the kit and it shows the 2 pipes and the oil pan gasket. Does this kit come with 2 pipes? It does not appear to include the gaskets for the pipes, only the oil pan gasket. Why would you need to change the oil pan gasket anyway? Mine were not leaking, so I left them alone. The pipes can be removed without removing the pan. It looks like I would need 2 kits (4 pipes) and then 4 additional exhaust pipe gaskets to do both of my engines.
The kit Part # is 04101-ZY3-010

I don't think there is any guarantee, but folks that have done the change out have not complained about having to replace the HO2 sensors. Aristikat (Jamie) has had a lot of experience changing out the pipes and dealing with the HO2 sensors on his older 225's. I would send him a private message and see what he has to say.