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'08 BF90D Falls on its face under heavy load

Mike - Given all the help you have provided people on this forum, you should write a book on diagnosing and fixing problems with Honda Outboards. Organize the book by motor size, then within each motor address diagnosis procedures, common issues, and common repairs. Self publish it and charge a substantial price. Alternatively, set it up on a seperate commercial website and allow folks to download on demand.
 
Have an 08 big foot Honda outboard with a real bad problem. It will run ALL day long at speed when I don't exceed 5000 rpm (the tach goes to 7000) I mean I have driven for 1 1/2 hours straight at 5000 rpm and no problems what so ever. When I push it above 5000 (doesn't matter what number it is 5500 6300 etc etc) the engine will randomly drop in rpm and then immediately go back to normal. It will do this continually until I back it down to 5000 rpm then no issue what so ever. Bump it back up then the mess begins again. Thought it might be water in the fuel but then it should be doing that ALL the time no matter the rpm. It is really bad because I am missing about 5-8 mph (It's a 26ft pontoon) and it is really dangerous because the boat basically stalls for a micro second and you are thrown forward. It feels like a stall or hesitation but it ONLY does it above 5000 rpm. Any thoughts or ideas?




ADD ON: This problem is very random in nature. I have gone flat out for 5-6 minutes and then it will start happening. Back off the throttle to under 5000 rpm and bam it WILL NOT HAPPEN. Only over 5000. (or 5000 on my tach) That being said you are not going to go flat out or even near the top due to safety issues for the passengers being thrown around.
 
Hi, all.
My 2008 engine number is 1010841 så it falls within the engines needing upgrade.
I bought my engine in 2010 so I don't know what was done to it by first owner,
However see attached image of my pump hoses. My upper hose goes to the low pressure filter, so it is the old pump then ?
Pump kit #22 on the image is for the affected engine numbers. Maybe it is the opposite, regarding where the hose attach ?
http://www.boats.net/parts/search/H... and Later/BF90DK0 LRTA /FUEL PUMP/parts.html
Mike said: "you will need part number 06167-ZY9-000. It includes the pump and three new hoses." But there are only two hoses on the pump ?

I have never experienced any trouble on full throttle. I get about 5,700 rpm WOT on my 18" RXB4 propeller.
How is that possible ?


pump1.jpg1800B.jpg
 
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Sorry for the confusion....there are two new hoses.

Why is yours running ok? There could be many reasons. I can only guess.

Your boat is easy to plane and the engine does not need much fuel once it takes off. The motors that I have seen that had this problem are pontoon boats, which do not plane.

It is also possible that you have less restriction in the fuel line feed from the tank. In every case that I had, I could temporarily "fix" the problem by bypassing the low pressure filter. Those boats did have an additional water separating fuel filter in line. Since they did, I did not hesitate to bypass the LP filter...until Honda came up with a fix for the problem.

So in summary....your boat probably planes easy; is not real heavy or may not have a antisyphen valve in the tank or does not have an external water separating fuel filter.

Your full throttle rpm seems low. 5700 rpm compared to max rpm of 6200. This is a sign of too much pitch in the prop (which can also cause a load on the engine...but does not seem to be causing you an issue). Going down one pitch or so will get you closer to
6200 and will give a faster takeoff (but probably slower top speed), especially if there are many people in the boat.

If the boat is running ok with no problems...and you are happy with it, just go out and have fun. Just keep in mind....if the motor starts cutting out at high prolonged speeds and squeezing the fuel bulb makes it smooth out, there is nothing major wrong and you know how to fix.

Mike
 
Thanks :)
My boat is not so heavy, I get 38 knots (almost 44 mph) @ a little below ideal rpm's with that 4 blade SS propeller, but I get excellent cruising speed.
I think that the advertised 18" pitch is much closer to 20" in reality. Maybe it's a 19" cast and Powertech forgot to adjust it down. And it has some cupping too.
However I can not load the boat with much people. I have tried a lighter propeller but did not get more top speed.
WOT rpm range is 5300-6300 but max power is @ 5800 rpm.
But I have an external water separating filter. First owner had a heavier boat, but no water separating filter that I know of. And just a 15" alu propeller.
 
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A Swedish tuning company says they can tune the BF90D up to 100 hp. Almost like the new 2014 Honda BF100.
That could solve the lack of rpm's, but maybe the engine needs more fuel then.. we will have to wait and see. I will probably try it.
However the BF100 has rised the rpm range to 5500-6300.
 
It seems there have been 4 different part numbers for the ECU depending on engine s/n.
Found it here on page 21 http://yp.anadolumotor.com.tr/hm/pdf/BF90DK0.pdf

First is ending with 003 for engine # up to 1000710.
Then ending with 013 for engine # up to 1006008.
Then ending with 023 for engine # up to 1015902
And finally 033 for newer engines.

My ECU part number is 34750-ZZ0-023. There is also another number wich I guess is a serial # for the ECU (7331-305754)
I just got a spare used -023 ECU from ebay because I will have my original one sent in to be remapped for more power.. at least I hope so.
The spare ECU has serial # 7331-301416.

Boats.net lists only the 013 and 023. Other sites says the 023 is superseded by 033.
Maybe all older numbers are superseded by 033 ?
 
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The 023 is the one that is installed in the Service Bulletin for erratic midrange rpm.

The 023 supercedes to 033. It guess it is assumed that the 013 is already changed out to the 023.

Mike
 
Thank you Mike :)

Does anyone know what changes or advantage there is with the 033 ECU ?
It is too expensive to buy a new one an anyway.
If a company is able to remap the ECU for more power, would they also be able to reprogram it to the 033 spec ?

What happened with all the old ECU's they changed out, are the reprogrammed by anyone or just thrown away ?
 
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Since you found a company to remap, I would ask them the question on remapping.

The old ECU's are probably ultimately thrown out.

Here's one that will complicate things. The new 90D has an ECU part number 34750-ZZ0-H01. It is not backward compatible with the older models that I can see. And....I can only guess what is different....I think it adds the NMEA2000 capability. I see that the wiring harness is different and the parts diagram includes the NMEA2000 interface cables...where the others did not. It may also do other things that I have not seen announced..

Mike
 
Yes, and Tohatsu has taken over the BF75D and BF90D (called BFT75 and BFT90), and Honda releases the BF80 and BF100.
The Tohatsu's don't have NMEA2000 as I understand.

Here is the tuning company http://lundinsmarin.se/
Most fun for owners of the Verado 135, as they actually have a racing program for this engine at around 235 hp.
 
Correction to my post #45: The new Honda/Tohatsus 75/90 hp has NMEA2000 connection. Found it in the owners manual online.
 
Hello to all Honda Guys.
My name is Chris and im From Greece. I have a Honda BF90D 2007 model and i have the same issues my engine is not reving up to 4000 rpms. I bought this engine used and he stay without working for 3 years i think. I have already change the fuel pump all the fuel filters the VST is ckean and the needle valve is working. I have change and the spark plugs already. I thought is from the propeller and i bought a new one but the probkem is still! Did anyone know something more??? The only think is to check the regulator fuel pressure!!!
 
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