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Not reaching max RPM

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nmastrandrea

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I have recently purchased a 2009 Regal. I took it up the coast from Virginia to NJ. Seemed to be running fine but I did smell gas. Figured it was a heavy mixture that an adjustment would do the trick. Brought it to a marina and I have not seen it for a month. They discovered 2 bent valves, 1 in each engine. There was no compression in cylender 8 of each engine. They did the repair and did a test drive. I get a call that the Max RPM they can get to is 4200 and it should be 4800 to 5000 and this could be the cause. Says that my props are out of pitch and that I will need new props. If i do not do this i will be lugging the engines and create pre detonation. any advice?
 
re:" seemed to be running fine"
At what RPM were you running?
Did you check to see how many RPMs you got at wide open at any time?
 
Well, your observed max RPMs pretty much agrees with what the mechanic told you. On most late model 5.7L engines, there is a MAX RPM range stated, usually on a decal on the flame arrestor (looks like an automotive aircleaner) . If your boat, with normal load in calm seas does not rev within this range, your prop pitch is incorrect. My guess is that the previous owner was dissatisfied with the speed of their boat and installed numerically higher pitch props thinking that their boat will go faster. Usually, the boat may go slightly faster but the max RPMs that the engine will rev to drops below the manufacturer's stated range. Running the engine under these conditions, i.e., with an incorrect prop, WILL eventually damage the engine, usually the exhaust valves.
 
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Thank you capt Bob. I will be calling regal tomorrow. She is equipt with twin 5.0 Volvo engines. Previous owners states that the props are original equipment so I am pretty confused as to why these props are out of pitch.
 
nmastrandrea said:
Previous owner had divers scrub the bottom monthly. Regal confirms that the boat should max RPM at 4800 to 5000
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Powerboat bottoms don't need monthly scrubbing unless they are raced!!!
Here on Barnegat bay less than 10% of the serious sailboat racers have their boat bottoms scrubbed by divers.

Soooo.... either previous owner BS'd you or may have made a habit of running the engines @ WOT.... not good for valves.

The place to start is to remove one or both of the props and bring them to reputable prop rebuilder to have them determine the actual pitch.

You said you "ran to NJ" Where in NJ are you?
 
The boat was in Smithfield Station, Virginia. I was told that is typical in that area. After speaking to Regal I found out that F6 props were original equipment for my boat. When you look at the specs from Volvo for the 5.0 GXI it calls for F5 Props. The marina may want to put F4 props on there. Presently at 3/4 throttle can get to 4200 RPM and then after that nothing. What is WOT? I am now in Barnegat Bay, Silver Beach. I did not find any Volvo Dealers by me.
 
WOT=Wide Open Throttle, How big is this boat? I assume you mean that 4200rpm is WOT rpm? Then you're lugging the engines. Either the engines are a little weak, or you're overpropped?
 
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sandkicker said:
............. If your boat, with normal load in calm seas does not rev within this range, your prop pitch is incorrect.
Or.... the engine itself is not up to snuff! I.E., not fully tuned or perhaps not healthy.

Running the engine under these conditions, i.e., with an incorrect prop, WILL eventually damage the engine, usually the exhaust valves.
I agree!
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I'm going to suggest that F-7's are too agressive for this boat.


Keep in mind that under Marine loads at/near 3k RPM and below, you're at a rather Detonation Prone RPM.
FYI..... Detonation and Pre-ignition are not the same phenomena.


.
 
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nmastrandrea said:
The boat was in Smithfield Station, Virginia. I was told that is typical in that area. After speaking to Regal I found out that F6 props were original equipment for my boat. When you look at the specs from Volvo for the 5.0 GXI it calls for F5 Props. The marina may want to put F4 props on there. Presently at 3/4 throttle can get to 4200 RPM and then after that nothing. What is WOT? I am now in Barnegat Bay, Silver Beach. I did not find any Volvo Dealers by me.
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I'm just down the road from you, my boat is docked at the Lavallette YC. Re: Volvo dealers in area. Closest Volvo parts from Monmouth Marine in Brielle. Horizon Marina on RT 37 (near the bridge, water entrance is from the Toms River) works on Volvos and understands them. Closest prop rebuilder is in Toms River, just off RT37 at the Manchester border, "Ocean Propeller". Per Rick and my previous post... you are "over propped".
 
sandkicker said:
I'm just down the road from you, my boat is docked at the Lavallette YC. Re: Volvo dealers in area. Closest Volvo parts from Monmouth Marine in Brielle. Horizon Marina on RT 37 (near the bridge, water entrance is from the Toms River) works on Volvos and understands them. Closest prop rebuilder is in Toms River, just off RT37 at the Manchester border, "Ocean Propeller". Per Rick and my previous post... you are "over propped".[/QUOTE

just wanted to update. I got the boat back and she runs great. F4 props were installed and max WOT is 4800. Although I won't be running her like that for fear of something like this happening again. Now I have four F6 props that have been fully reconditioned to sell!
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just wanted to update. I got the boat back and she runs great. F4 props were installed and max WOT is 4800. Although I won't be running her like that for fear of something like this happening again. Now I have four F6 props that have been fully reconditioned to sell!
 
Good for you! Thanks for letting us all know! You should be able to sell those props easily, Good Luck,
Mike
 
Just did read the thread. Excactly same experience as I did put the 15x17" prop to my Windy23FC/VP431A. 205HP. Did reach just 4000RPM, and eng. was heard 'crying'. ! Install of 15X17 was done because original 15X15 prop was so rotten that stampings were unreadable..guessin hardly visble last digits 17 instead of 15. Now has 15X15 LH, and eng does reach 4400. runs smoothly and engine heard smiling. Regards, Esa
 
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