1978 25' bayliner 5.7 penta top speed?

Hello just bought a 78 bayliner with a 5.7 and penta 280. At wot the rpms wont go past 3,000-3'100 and the fastest i can get it is 15-16 GPS. Is there a way to adjust the linkage or could the prop be wrong? It sounds like its working harder than it should. also when out of gear it can be reved higher than 3,000.

Re: 1978 25' bayliner 5.7 penta top speed?

Not sure how fast 15-16 gps is? could you relate that in MPH?

3000-3100 is low RPMs for that engine. What is your prop size?

Your boat should be proped to achieve max stated RPMs at WOT with normal (however you use the boat) load.

Also you may need a tune up and timing check if you are not getting over 3K RPMs unloaded.

I would also pull the distributor cap and check the rotor. You should be able to turn it a little back and forth against the advance springs. If it is frozen or real stiff you probably need to pull the breaker plate and de-rust and lube the advance weights and cams to get proper WOT timing advance.

Re: 1978 25' bayliner 5.7 penta top speed?

sorry i was refering to 15-16 mph as read on gps. Im not sure what size the prop is as the boat is in the water and im not sure where to look. It does have a somewhat recent tuneup and will rev smoothly all the way to redline when out of gear. I dont know what this engines WOT rpm is.

Re: 1978 25' bayliner 5.7 penta top speed?

It does have a somewhat recent tuneup and will rev smoothly all the way to redline when out of gear.

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Ayuh,... Totally Irrevelant,... Motors without Load will rev to the Moon, with 1/2 it's cylinders Dead...

Do a Compression test to see the general condition of the motor...

Also,... Have a look Here...

Re: 1978 25' bayliner 5.7 penta top speed?

Did you have a survey done before purchasing it? Or did you or a mechanic look the engine over?

How does the hull/outdrive look? ie: algea or no?

Check the oil level for overfill...

If you just installed a prop that would be my first guess.

Like Bond-o said, they'll rev just fine with no load on them...even when they're real sick.

Re: 1978 25' bayliner 5.7 penta top speed?

Like Bondo suggests...you should do some diagnostics on the engine before you start spending any money. If you are only getting 3000 RPM at WOT under load then it's not the prop. Is the tach actually reading correctly? Are are all 8 cylinders firing? What do the spark plugs look like. Do you have good compression on all cylinders? Is the timing set correctly?

Re: 1978 25' bayliner 5.7 penta top speed?

List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

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.

Re: 1978 25' bayliner 5.7 penta top speed?

Bubba1235 said:

On that old a Bayliner the very first thing I would do is weigh it. They are notorious for water logged foam.

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A 25 ft boat is not going to have any foam since it isn't required to have foam.

Re: 1978 25' bayliner 5.7 penta top speed?

I think 4500-5000RPM is max and around 30mph if every thing is good-tip top condition.

my HEAVY 26ft 1984Wellcraft with a 1996 7.4L (300hp)Mercrusier/bravo3 will hit just over 40mph GPS at 4600 rpm (wfo)trim & tabs up.

start simple on Don S list-something(maybe several) is slowing you down.You need to reach higher rpms.
Good Luck
-Joe

Re: 1978 25' bayliner 5.7 penta top speed?

When you finally figure out if your engine is running correctly, look for the Volvo "Elephant ear" style props. They seemed to work the best on our 27' Bayliner Victoria Sunbridge that we used to own.