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Honda 225 - won't respond to throttle over 4200 RPM

brettmarl

Regular Contributor
I bought an old USCG boat a few years ago that came with a pair of 225's. Can't figure out how to tell year from model or serial, but here's the model/hours:

Port: BF225AK1 XXCA with ~2100 hours
Stbd: BF225AK3 XXA with ~270 hours

They have been bomber so far, but recently the older Port engine started having issues a few weeks back. It starts normal, sounds normal, but won't go over 4200 RPM. Applying additional throttle doesn't do anything, no stall or weird sounds.

A few weeks prior to this I noticed that the Port engine starting consistently burning +2 GPH than the Stbd - which was a change - as they have been almost identical matched on burn for the two years I've owned it.

Had the local Honda shop go through the engines in January this year. Replaced hi-low filters, timing belt, tstat, plugs, impeller, did valve-adjust etc. One comment on the Port engine was "VST drain screw seized - was unable to break loose". Also had them install new throttle cables back in July.

Only other maybe related change I can think of is that I accidentally ran a half-tank of E10 through it around the time (unfamiliar fuel dock - and I didn't realize marina's sold anything but e-free, by the time I realized, it was in), but that fuel has long been used up.

Checked the transom water-separators to see if any obstruction or water, they seemed fine.

I'm kind of a mechanical newbie - so go easy on me - but wondering if there's anything obvious/easy I can self-check before I make the trek back to the Honda shop. Boat is on the water and it's tricky for me to get it out - so it's not that easy for me to start tearing into engines...

Here's a piccie of the boat if it helps inspire a reply ;)


boat.jpg
 
Check and see that the throttle is opening fully.Then you need to start with checking condition of spark plugs, ie remove and compare , they should all be the same color. Whilst out do a compression test.
 
Check and see that the throttle is opening fully.Then you need to start with checking condition of spark plugs, ie remove and compare , they should all be the same color. Whilst out do a compression test.

Thank for suggestion. Maybe a silly question - but any tips for doing plug extraction / compression test on water vs on land. I’m kind of nervous to drop one of those ignition coils in the drink. Is it safe to fire up engine for compression test with engine tilted all the way up and hose connected to flush port?
 
You can work on engine fully tilted. You have AK motors so the bottom cyl on the port side has a removable piece in the lower cowl to facilitate removal of the igniter. You do not run the engine for a compression test so no need for hose. Do you know how to perform a compression test?
 
Maybe not :)

i thought i pull all plugs, pull fuel pump fuse and stick
a gauge on each cylinder in turn and crank the engine to read compression gauge.
 
Don't know where to start. Since you only make it to 4200 rpm and nothing happens beyond that on the throttle, and no misses or stalls, the first thing I would check is the throttle opening as Ian suggested. If it's not opening all the way then you need to adjust the throttle cables. Below is the procedure that I wrote up several years ago...

First, with engine off, take off the cover, gently put in gear (do not force it – if much resistance, get someone to turn the prop by hand while slipping it into gear), push throttle full open and inspect whether the throttle lever arm (at the cable cam wheel) is up against the stopper. It should be.

If not, before adjusting, pull throttle back to idle speed, put shifter in neutral, and follow the cables to the throttle cam wheel (on top of the engine toward the rear) and make sure they are not damaged or kinked.

At the throttle cam wheel, make sure the adjustment nuts are tight. Measure the distance between the adjustment bracket and the end of the cable adjustment threads. They should be 9 mm on both. If not, adjust.

Back to the throttle cam where the lever is located - measure the length from the end of the threaded part back to the adjustment nut - the open side (to your left as you are facing it) should be 14 mm. The close side (to your right) should be 19mm. If not, adjust.

Put back in gear, and push throttle all the way forward. Throttle arm on the cable cam should be up against the stopper. If not, then you likely have a problem with the cable from your throttle control to your engine, which will need to be adjusted or replaced.

If the throttle arm is up against the stopper, then look at where the roller sits in the throttle cam. It looks like a fat inverted "L". The roller should be almost touching the top of the narrow part of the "L".

Then pull the throttle lever at your control all the way back, and put the engine in neutral. The roller should now line up with the "V" mark on the foot of the "L." If not, adjust the linkages until the roller does what it is supposed to do – nearly touch the stopper at full throttle and line up with the "V" mark at minimum throttle.

For more detail, see pages 3-18 to 3-21 in the Helm Shop Manual. Below is a link to the helm shop manual for the older 225's. I think the cable adjustment procedure is the same for the newer AK models.
 
Thanks. Interestingly I’m out on boat right now. Just jumped a big wave and now port engine is happily going up to 5k again. I’m thinking loose spark plug maybe? Will dig in tomorrow.
 
Yeah - on reflection that feels more likely given a) the new throttle
cables back in July and b) no weird noise/shaking that I assume I would hear with a non-firing cylinder. I’ll try your throttle adjustment procedure
first.
 
Btw - thanks for link to pdf. I bought the physical copy off amazon but usually leave it on the boat. So nice to be able to look at it at home on my computer instead.
 
Aliboy makes a good point. Have you tried to pull fault codes on the engines? A bad HO2 sensor (or failing spark plug, failing coil, or fuel pressure out of spec) will throw a Code "1".
 
Good idea. My MIL light is not on. Will shorting the plug show me stored codes? I assumed that trick was for current MIL status and I needed a fancier tool to read stored stuff.
 
Yes. Codes stay in the EPROM until cleared. Typically you will read stored codes then clear them. Run engine again and look for new codes. Procedure has been procedure has been posted on this forum many times.
 
Once had a bad O2 sensor on one of our BF175's that didn't throw a code but we noticed it by the fuel burn difference. Swapped in a spare sensor and all good.
 
Got out to the boat today in order to try some of the suggestions above:

1. No stored faults in the engine. Shorting the pins and turning on just left MIL and Battery Lights solid.

2. On inspection the lower throttle-arm cable adjustments were in different positions between P and S engines (see pic)

cables.jpg

They seemed quite different which strikes me as odd - the Honda dealer just put new cables in back in July - and it doesn't look like 'cable stretch' or anything weird, I wonder if they they had a reason to set them up this way?

I decided the follow the manual and went through the adjustment procedure, the arm almost hit the stop - but was short about 1mm, I adjusted the rod so that it hit.

In my shop manual for the upper throttle cam, it says 9mm for A5 and earlier engines but 13mm (open side) and 11mm (closed side) for A6 and K0 engines. This is a K1, so I went with the 13/11 measurements, which is what they were already set to.

I was working alone, and my shifter would not push forward - chawk_man's notes above suggested having someone rotate the prop while pushing forward if this were the case, I found that raising the engine while pushing the shifter had the same effect as water rotated the prop on the way up.

Per the last step in the manual - I had to muck with the top adjustments again (back in neutral position) quite a bit in order to get the little triangle in the center of the pin.

Did quick sea trial - and it's better, but not perfect. I was able to get port engine into 5200 range, while starboard was doing 5800 WOT.

It's also weirdly inconsistent, at first launch it doesn't like going into the higher-RPMs (stops around 4200-4400) until it's been running for a few minutes, then the RPMs surge a little and it responds happily to throttle adjustments. Which is actually the original behavior as it started deteriorating - couldn't get over 4200 on launch, then after a few minutes underway - it worked normally - eventually, not allowing me to go over 4200 at all.

I have no idea how old the O2 sensor is - but it looked a little crusty on the outside, so I ordered a new one and will swap it out to see if it stabilizes things and/or improves the fuel-burn. Can't hurt to have a spare if it's a no-op.

3. I tried to pull plugs to inspect, but didn't have a 6mm allen key - so will have to do that another day.

Great improvement so far though - thanks for all the help/pointers!
 
Hmmm. Weird. Take a really close look at those cam wheels again, both the ones on top and the ones down by the throttle control. Could be they are sticking or out of alignment. Disconnect cables and rotate the cams looking for binding or out of alignment.
 
Just a comment, I as a dealer don't use the measurements, that is a guide, it's easy to fit and adjust through trial and error and then sync the throttles using the main control cable adjusters. As long as the throttle is fully open at WOT and on the stop at idle you're good to go.
 
Couple of follow-ups on my progress:

Since cable adjustment, seems happy going all the way to about 5200 now and then it's capped again. Fuel burn discrepancy still there - I swapped O2 sensor for new OEM one. Old one looked a bit crusty (see pic), but didn't seem to make a difference on fuel-burn.

Took it in to Honda dealer today to get it inspected. Didn't find anything at dock via Dr Honda, but on the sea-trial they noticed that the TPS would only report 75% throttle, so think it's starving for fuel somewhere - however they need to pull it out the water and dig in more to find the root cause. I'm on their schedule a few weeks from now for that.

IMG-0912.jpg
 
Soak that HO2 sensor in gasoline for at least 24 hours, occasionally moving it around. Clean and dry it and keep it for a spare.
 
Engine went under the surgeons knife today at Honda dealer... verdict is high pressure fuel pump failing (low pressure ~ 25psi) and TPS sensor is also failing. So needs new throttle body, new HP fuel pump and recommended a LP fuel pump while he's in there given hours.
 
Hmmmm. If problem is with HP fuel pump and TPS sensor, why do you need a new throttle body? Or is there some other problem with that?
 
He said they can’t replace just sensor it need a complete
throttle body? Sounded odd but I assumed it was a built in sensor?
 
Yes, that does sound odd. First of all, a malfunctioning TPS should have given you an alarm and a fault code 7.

Having said that, there is no separate TPS listed on any of the BF 225 parts diagrams I looked at. The Helm manual (page 5-33) tells you how to test it, but does not tell you how to replace it. Hard to believe that it is not a separate part in light of the fact that every Honda auto engine I've ever seen has it as a separate part.

Can anyone on this site confirm whether or not it is a separate part?
 
Hey @chawk_man - would appreciate your thoughts on some of what the Honda dealer is telling me... some of it seems a bit conflicting.


1. Verbally the tech told me that the "TPS was only reading 80% at WOT", so probably faulty and needed replacing. On paper they wrote "Only getting 79% TPS at WOT" as the issue. The correction notes say:


"Port engine had a bad TPS and bad high pressure fuel pump. Recommended replacing the low pressure fuel pump and checking valve adjustments. Removed the VST for putting the fuel pump and the throttle body. Put in the new high psi and low psi fuel pump and some new fuel line. Adjusted the valves and put engine back together. Started and checked for fuel leaks, check the TPS and it is showing 80% at wide open. We'll check to see if it changes when running the engine and how it performs. -- Sea trialed - both engines ran well at 6200 RPM."


I asked them if the TPS still only showing 80% at WOT is a concern (as suggested in the notes), and they replied with "The TPS sensor at 80% at WOT is normal".


2. Last year they did my valve adjustments a few weeks after I'd just changed my oil and crank case fluids elsewhere. I told them not to change the oil but they were adamant that I had to change oil again at the same time as a valve adjust because quote: "the oil can be contaminated from debris coming loose from the valves and combustion chamber".

This valve adjust, surprisingly, they didn't change the oil, and I asked them why not - reply was "​oil looked ok and we covered everything up when doing the work".

Boat is finally ready for pickup and excited to get it back :)

I'm going to change the oil in a few weeks anyway when I pull her out for winter, but I'm wondering if you guys normally change oil at same time as valve adjust for that reason. Also any idea is TPS 80 @ WOT is indeed normal?
 
The TPS works on a potensio meter as the butterfly's open it registers a voltage to the Ecu the more it opens the voltage it registers increases if the ECU is not getting the correct voltage from the TPS it doesnt know how much air has come in and doesn't know how much fuel to deliver when your mechanic talks about 80% .you need to know the correct voltage the TPS should deliver at WOT
 
I've never had to fool with the TPS on my engine, so I can't help you there. Testing procedure starts on page 5-33 of the helm manual. Voltage to TPS should be between 4.75 - 5.25 at closed throttle. Not sure it's the same for a K1 engine.

I've never thought it's required to change the oil after a valve adjustment. The oil filter should take out any carbon particles that may come loose.
 
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