VP wont go pass 3500rpms

[imrtommy]

long story short i had a 1999 VP 5.7l GI engine and the block cracked. my cousin who fixes yatchs took a "suppoesly" 2004 vp 5.7l duoprop off of it cause the owner wanted mercruiser engine. bought it from him for 3k installed works like a beauty except the rpm wont go pass 3500rpms on my 21ft center console. also it is not fuel injected, i put the old carb. onto the supposedly 2004 engine. searched the engine for numbers but all it says is "5.7L GM" and number 2 right behind the valve cover. can anyone help? i was thinking about buying a 4bbl carb but didn't want to waste money.

i did a search but without the name of the engine it doesn't help me much at all... sorry but can someone please help?

 

[cr2k]

Re: VP wont go pass 3500rpms

Did you check for WOT in the carb? Is it getting full open butterflies?
Maybe a linkage adjustment.

Which distributor did you use the one with the new engine or your old one?

If old one you may need to reset the advance curve to match the cam since you are carbing a FI engine. Take a timing light and a friend out on the water and go WOT and check timing advance.

 

[cr2k]

Re: VP wont go pass 3500rpms

Did you check for WOT in the carb? Is it getting full open butterflies?
Maybe a linkage adjustment.

Which distributor did you use the one with the new engine or your old one?

If old one you may need to reset the advance curve to match the cam since you are carbing a FI engine. Take a timing light and a friend out on the water and go WOT and check timing advance.

Or maybe that is why he is changing engines?

 

[imrtommy]

Re: VP wont go pass 3500rpms

Timing was good at home but not under load. Will check this sunday. Thanks for the help guys.

 

[cr2k]

Re: VP wont go pass 3500rpms

You may need to pull the breaker plate out of the distributor and lube the cams and weights so they will go full advance.

 

[Don S]

Re: VP wont go pass 3500rpms

You may need to pull the breaker plate out of the distributor and lube the cams and weights so they will go full advance.

Hard to say what engine he has exactly, but if I am reading it correctly, he now has a 2004 engine (Complete) installed in his boat. If that is the case, he has the EST distributor, no weights all electronic.

To the original poster, do you have a Volvo SN for this engine? Should be on a tag on the Port side of the engine back near the flywheel.
Then we can post some info on what you actually have.

Here is a list of possibilities that will cause low WOT rpm.

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[ENSIGN]

Re: VP wont go pass 3500rpms

As Don stated,check the compression!

 

[havasuboatman]

Re: VP wont go pass 3500rpms

As Don stated,check the compression!

If you can't fix your problem using Don's list, brother, it ain't broke.
Here's a little tip though, ALWAYS check the easy stuff first, before you start replacing parts.