Honda 2008 OB 150hp wont rev to 5500rpm at full throttle stays at 4000rpm (Sometimes)

[cguella]

I have a 2008 Honda 150hp that I bought new, is under warranty, and is OEM maintained annually. At some point in the season at full throttle it stops revving to 5500 RPM instead when at full throttle it revs up to 4000-4200 and sits there (Boat at 18mph). And then sometimes woosh it will spin up all the way to 5500 rpm (Boat at 32mph) and stay there until I throttle down. I may or may not rev back up to 5500 rpm again on the next acceleration. It is bizarre (Also bad for towing skiers and wakeboards). The engine starts and runs - no problem. The only issue is the rev to full throttle and missing the power curve that comes at full throttle. The difference takes the boat from 18 to 32 mph so it matters a lot.

Any ideas on what might cause this?
Do you think it is fuel or engine/engine tuning related.

THANKS.

[cguella]

Honda states that the VTech kicks in around 4700 RPM so I wonder if something is potentially wrong with that system AND/OR fuel issues both could be contributing to this problem.

[cp]

...is under warranty, and is OEM maintained annually.

That being the case, suggest you take it to them so they can read what the computer has stored regarding this issue and then fix it for you. It may be a clue that your motor stalls out at the rpm where the VTEC is supposed to kick in, but it's prob'ly not a good idea for you to mess with it and risk voiding your warranty. Just my 2¢.

[boatsngoats]

well Vtec is a possibility.. somehow, I doubt it. Its pretty solid of a system as long as the oil changed have been kept up.

If I were the Tech looling at it, I would look at the TPS and the Throttle linkages to make sure the Throttle plate is opening all the way. And if it is.. Making sure the HDS (Honda Diagnostic Tool) sayes the ECM is recieving the singnal. The TPS has a hot output of .5v at idle and 4.8v- 5.0v at WOT. If the ECM is getting a signal from the TPS that is 4.4, and you have the HAMMER down... the engine is only going to run at 3/4 throttle.

Other than that... the HDS will also say if there was a problem with the VTec... but more than likely, a tech is going to plug it in and everything will be GREEN for GO! and it wont say there are any issues at all.

Then you just hope you have a decient mechanic and not a parts changer. Honda makes it fun when it comes to these issues because I could be completely wrong and your enging is having grief with a MAP sensor.

Good LUCK.. but you should probably take it in.

[cguella]

They say diagnostics pointed out a VTech switch. Swap out of VTech "switch" led to no change. Still troubleshooting. I passed on your comment to authorized Honda repair who is running diagnostics again this week. Thanks.

[portlandsparky]

I am having the exact same problem with my 2006 OB 135hp. Please keep me in the loop what they find out.

Adam

[hondon]

Even though this has been OEM maintained,many techs overlook or avoid the high pressure fuel filter because of accesability issuses.That filter can offer up your exact symptoms.Check your invoices and see if there are at least two if not three fuel filters listed.One should be the primary boat mounted water separator,next should be the engine mounted filter, and finally the high pressure filter on the output side of the vapor separator.If that hp filter has been ignored we may be going in the right direction.

[cguella]

well Vtec is a possibility.. somehow, I doubt it. Its pretty solid of a system as long as the oil changed have been kept up.

If I were the Tech looling at it, I would look at the TPS and the Throttle linkages to make sure the Throttle plate is opening all the way. And if it is.. Making sure the HDS (Honda Diagnostic Tool) sayes the ECM is recieving the singnal. The TPS has a hot output of .5v at idle and 4.8v- 5.0v at WOT. If the ECM is getting a signal from the TPS that is 4.4, and you have the HAMMER down... the engine is only going to run at 3/4 throttle.

Other than that... the HDS will also say if there was a problem with the VTec... but more than likely, a tech is going to plug it in and everything will be GREEN for GO! and it wont say there are any issues at all.

Then you just hope you have a decient mechanic and not a parts changer. Honda makes it fun when it comes to these issues because I could be completely wrong and your enging is having grief with a MAP sensor.

Good LUCK.. but you should probably take it in.

The techs have honed in on the TPS using your feedback and measured that it was not getting/giving the right voltage at full throttle so the next step is to replace the TPS on the engine and then retest.

[supwhoaday]

Did you ever fix your problem? I haves BF115 4 stroke that is doing the same thing.

[cguella]

Did you ever fix your problem? I haves BF115 4 stroke that is doing the same thing.

Supposedly, although with only a single water test to confirm. Since it was intermittent - I will know more in a few weeks when I am able to get back on the water for a few hours. I'll report back then. But the voltage test did show low voltage at full throttle supporting the problem so all things pointed to the TPS and its replacement.

[supwhoaday]

My motor stays at 3300 rpm WOT. I have a 20' Sportcraft CC with a BF 115 4 stroke. The motor starts and idles normal. Throttle response is also normal but can only rev to 3300 rpm when under load. My GPS says my boat is doing 36 mph at WOT(3300) and I think the tach could be faulty. I checked almost everything you could possibly check but still no promising result. Hope all goes well for you chia la!

[cguella]

After extensive water testing this problem seemed to have returned after I thought it was resolved. Now the problem has resurfaced and I am at a loss as to why...