Idles great has no power on take off 2000 5.0l 305 Mercruiser

[chaparral 5.0]

idles great, put throttle to it and won't plane, heard kind of a snapping sound. It's a 2000, mercruiser 5.0l, 305, carb rebuilt in dec 08. Runs on trailer then rpms drop once it hits 5000 rpms. Told might be coil, or plug wires?

 

[oops!]

Re: power loss on 5.0l 305

Re: power loss on 5.0l 305

hi chap.....welcome to i boats.....

on this site we have the best motor tech's in the world....bar none.

also one person here is considered the best diagnostition any where....

do exactally as they say....you be thier eyes ears and hands and you will be on the water is no time. !....really ...im not kidding.

but first we have to get this moved to the i/o engine forum.....


cheers
and welcome to the best boating site in the world

 

[QC]

Re: Idles great has no power on take off 2000 5.0l 305 Mercruiser

idles great, put throttle to it and won't plane, heard kind of a snapping sound.

Could that be knocking? Pinging? How old's the fuel? Timing? Last tune-up?

Runs on trailer then rpms drop once it hits 5000 rpms.

Sounds like the rev limiter, and is supposed to keep it from splattering if you rev too high in neutral . . . Just don't do that anymore and you won't have to worry about that particular issue. In all seriousness, 1500 RPM max on the Muffs (trailer). The hose can't supply enough water for more than that. Even 1000 starts to suck hose flow dry

Take a look in the Adults only section ^^^^^^ there is a low WOT RPM link in there (#12). I'd start there. Good luck!

 

[Brew2]

Re: Idles great has no power on take off 2000 5.0l 305 Mercruiser

I believe 5000 is the maximum WOT RPM for that motor. If you are actually getting to 5000 RPM in the water, then you problem isn't the motor, it is the prop and/or outdrive.

 

[Don S]

Re: Idles great has no power on take off 2000 5.0l 305 Mercruiser

Runs on trailer then rpms drop once it hits 5000 rpms.

First of all, trying to run an engine at full throttle in neutral and out of the water is not only a NON Test, A V8 engine running on only 2 cylinders will run 5000rpm without a load. it's a good thing you tried it on a newer Merc with the Thunderbolt V Ignition system. It has overspeed control. At 5100 rpm, the spark is shut down till the rpm is below 5000.
Here is from the manual.

OVER-SPEED CONTROL
The Ignition Module will prevent the engine speed from exceeding a preset limit by stopping the spark. The over-speed limit is set slightly higher than the top end of the rpm range. For example, if the recommended range is 4600-5000 rpm, the over-speed limit would be set at 5100 rpm. When rpm reaches this limit, spark is turned-off until engine rpm drops down to a RESET rpm, which would be approximately 4750 rpm for this example. At this point,
spark comes back on.

Since it sounds like you also have pinging going on you might want to be checking the operation of the spark advance.

I would also suggest you head up to the Adults only sticky at the top of the forum and download manual #24 for your engine. Time to do some testing, and not just throwing parts at it because "Someone said it might be"

 

[fabrimacator21]

Re: Idles great has no power on take off 2000 5.0l 305 Mercruiser

Did it run ok for a while after the carb rebuild?

Check your spark plugs... if they are white and chalky, you have a lean condition which will cause pinging.

 

[Bondo]

Re: Idles great has no power on take off 2000 5.0l 305 Mercruiser

Did it run ok for a while after the carb rebuild?

Check your spark plugs... if they are white and chalky, you have a lean condition which will cause pinging.

Ayuh,... And Change the Fuel Filters...