99 VP 5.0GL down on power.

[mikeneal]

I have a 99 Vovlo Penta 5.0 GL with about 700 hrs on it and it has been down on power lately. I do a ton of wake boarding and typically have a lot of weight (ballast) in boat so the power decreases super noticeable. (struggles to get on plane). The tune up is relatively fresh (~50 hrs) and I checked easy stuff first. (throttle linkage etc. to ensure it is going WOT, all checks OK). It runs smooth, good idle etc so I doubt it is valves or something internal etc. I have not done compression test lately but plan to do that for warm and fuzzy. I checked timing advance and my factory manual says it should start at 3degree at 600 RPM and go to 26 BTC at like 3400 RPM and above. I checked it today while boat was in water and it stopped advancing at 22 degrees. The mechanical counter weights seem to operate smoothly by hand and and rotate as far as they are supposed to. What would limit the total advance and think that is it? I also noticed that although the motor has 4 barrel intake , it has adapter plate and holly 2 barrel so I might upgrade to a holly or edelbrock carb 4 barrel. I would hate to give it low end torque though (wake boarding). I suppose a properly adjust carb with secondaries would not though...true? Any thoughts on the timing and power decrease?

 

[Coors]

Re: 99 VP 5.0GL down on power.

First, check the compression.
A wake-boarding really stresses the engine, like lugging it.
The combustion gases get between the pistons and rings, pushing the rings harder against the cylinder walls; more wear on both; more clearances than normal.

 

[Coors]

Re: 99 VP 5.0GL down on power.

and that may have also put slop in your timing chain, the total advance problem..

 

[mikeneal]

Re: 99 VP 5.0GL down on power.

I thought with slack in the timing chain the timing would oscillate somewhat and/or have some noise?

and that may have also put slop in your timing chain, the total advance problem..

 

[mikeneal]

Re: 99 VP 5.0GL down on power.

I checked copression and replaces plugs (since they were out). Compression is about the same as it was last time i checked ~250 hrs ago).
#1

opps mis post...delete if possible

 

[mikeneal]

Re: 99 VP 5.0GL down on power.

I checked compression tonight and changed plugs, compression was about the same as it was ~250 hrs ago.

Results:
#1 172psi
#2 160psi
#3 169psi
#4 170psi
#5 175 psi
#6 165psi
#7 172psi
#8 170psi

Numbers look good too me, so I guess it is not major internal problem.

 

[mikeneal]

Re: 99 VP 5.0GL down on power.

Any new thoughts , I am about out of ideas myself.