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150 HP Honda 4 stroke- lower RPMs

O

OBX Outdoorsman

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<p>
I have a 2015 Honda BF-150 outboard. I started noticing lower RPMs and felt like the worn stainless prop may be the cause. I took the prop to a reputable company that repaired the worn prop and am still experiencing lower RPMs and therefore lower top speed and its slower to get on top. Its pegging out at about 4,600 RPMs and in the past its been closer to 5,500.  I have solely run non-ethanol fuel and have replaced my Racor water separator.  Any suggestions on what to try next? Thanks in advance!!!</p>
 
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[FONT=&quot]Could be several things:[/FONT]
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[FONT=&quot]Do you have a digital or analog tach if digital should be accurate if analog it might be off [/FONT]
[FONT=&quot]If tach ok
Check primer bulb for air could be cracked
Check for kinks in the fuel line especially from the fuel water separator on the boat to the primer bulb.
Check control grommet fuel tube passageway is not pinching fuel line due to bending of cables when engine tilted.
Check for internal delamination of the fuel lines going to and from the boat fuel water separator to the primer bulb, I have seen internally delaminated fuel lines cause similar rpm reduction problems on optimax engines.
Is there an air leak in fuel system due to leak in the gasket of boat fuel water separator, pull separator and feel the top of mount where it meets the gasket make sure it feels smooth if gritty scrap surface with a razor blade.
Check or replace orings on the engine fuel water separator and fuel filter, I've seen leaks at the cup o rings and replace high pressure filter it might be clogged or soft like a wet sock..
[/FONT]
[FONT=&quot]Check for throttle cable stretch, does it rev to 5500 in neutral don't check this for long or do it a bunch of times just see if it will get to 5500 in neutral? [/FONT]
[FONT=&quot]
[/FONT]
[FONT=&quot]Could be old fuel in the tank try running engine on hand tank with known good fuel, carbon in the engine run some power tune or ring free in the fuel.[/FONT]
[FONT=&quot]
[/FONT]
[FONT=&quot]Loss of compression from valve seating can be adjusted out, Check compression with a good quality compression tester not harbor freight one. if compression is low engine not developing enough power to turn prop you had. [/FONT]
[FONT=&quot]
[/FONT]
[FONT=&quot]Check small pressure regulator vacuum tube on the top of the fuel rail is connected and not split.[/FONT]
[FONT=&quot]Vacuum tubes there are several to IAB control valve has anyone removed the belt cover lately?[/FONT]
[FONT=&quot]
[/FONT]
[FONT=&quot]VTEC solenoid valve 4300 rpm see if you can hear VTEC solenoid working when revving in idle to 5500[/FONT]
[FONT=&quot]or stuck rocker arm assembly Page 10-16[/FONT]
 
I appreciate your help. I will use the information that you so kindly provided to try and determine this issue. Once I have done so, I will be sure to let you know. Thanks again!

HonDan said:
[FONT="]Could be several things:[/FONT] [FONT="] [/FONT] [FONT="]Do you have a digital or analog tach if digital should be accurate if analog it might be off [/FONT] [FONT="]If tach ok Check primer bulb for air could be cracked Check for kinks in the fuel line especially from the fuel water separator on the boat to the primer bulb. Check control grommet fuel tube passageway is not pinching fuel line due to bending of cables when engine tilted. Check for internal delamination of the fuel lines going to and from the boat fuel water separator to the primer bulb, I have seen internally delaminated fuel lines cause similar rpm reduction problems on optimax engines. Is there an air leak in fuel system due to leak in the gasket of boat fuel water separator, pull separator and feel the top of mount where it meets the gasket make sure it feels smooth if gritty scrap surface with a razor blade. Check or replace orings on the engine fuel water separator and fuel filter, I've seen leaks at the cup o rings and replace high pressure filter it might be clogged or soft like a wet sock.. [/FONT] [FONT="]Check for throttle cable stretch, does it rev to 5500 in neutral don't check this for long or do it a bunch of times just see if it will get to 5500 in neutral? [/FONT] [FONT="] [/FONT] [FONT="]Could be old fuel in the tank try running engine on hand tank with known good fuel, carbon in the engine run some power tune or ring free in the fuel.[/FONT] [FONT="] [/FONT] [FONT="]Loss of compression from valve seating can be adjusted out, Check compression with a good quality compression tester not harbor freight one. if compression is low engine not developing enough power to turn prop you had. [/FONT] [FONT="] [/FONT] [FONT="]Check small pressure regulator vacuum tube on the top of the fuel rail is connected and not split.[/FONT] [FONT="]Vacuum tubes there are several to IAB control valve has anyone removed the belt cover lately?[/FONT] [FONT="] [/FONT] [FONT="]VTEC solenoid valve 4300 rpm see if you can hear VTEC solenoid working when revving in idle to 5500[/FONT] [FONT="]or stuck rocker arm assembly Page 10-16[/FONT]
Click to expand...
 
Hi OBX,
What HonDan says about checking the VTEC solenoid sure makes sense to me because of the 4600 rpm thing. All his suggestions seem appropriate

I was wondering if you have ever cleaned the VST or changed the filter? I know it can get gunked up in there over time and cause problems.
Just a thought.
Good luck.
 
Apologies for the redundant suggestion above. I have been having "issues" of late posting on this site.
 
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