Boat won't go fast.

[erock270]

I have a 4 cylinder Volvo Penta 270 in a 19ft Bayliner. When I take it out it gets 3000rpm but only does about 30mph with just my wife and myself on it.

 

[Gary H NC]

Re: Boat won't go fast.

It should get above 4000 rpms..( around 4500)
When was the last full tune up?
Including timing set,dwell and all new parts? Plugs,wires,cap,ect....
Fuel filters changed?

 

[steelespike]

Re: Boat won't go fast.

What is the overall performance like.start good?how is the hole shot(acceleration)?Are all the plug wires hooked up?Check the compression.
What size prop.Usually on the barrel or under the prop nut.

 

[erock270]

Re: Boat won't go fast.

I do not know when the last tune was due to me only owning it for about 2 months. The hole shot is fair. It starts up and idles very smooth. The prop does not look too bad it has one good ding in it but other than that it looks good.

 

[htv]

Re: Boat won't go fast.

Are you saying it tops out at 3000 rpm? Or that at 3000 rpm it only goes 30 mph? If it's the latter I'd say that might be pretty close to normal for a 4 cyl. for a 19'.

 

[erock270]

Re: Boat won't go fast.

It tops out at 3000rpm and 30 mph with just my wife and myself.

 

[180shabah]

Re: Boat won't go fast.

You need to verify some numbers. What is your prop pitch and drive ratio?

I plugged in 2.0:1 and had to use a 21" prop to get a theoretical speed of 30mph at 3000RPM. Actual speed is always lower due to prop slippage. Are you certain that the tach is accurate and was the speed checked with GPS or the dash speedo?

 

[htv]

Re: Boat won't go fast.

Does it have power trim to get the nose out of the water?

 

[fcawth]

Re: Boat won't go fast.

You really should check the tach. Something is not adding up, because 30mph at 3000 rpm is fairly fast for a 3.0L on a 19' boat. Check to make sure the tach is switched to the correct # of cylinders (small switch usually on the back). I'm propped for pulling on my 17.5' with 3.0 1.97:1 ratio and 19 pitch prop, and I get 30mph at about 3600-3800, topping out at 40mph when it hits 4600RPM, at which point I have to throttle back. I have it propped this way to pull skiers. With a 21 pitch prop I'd guess I would be at 3400 RPM or so at 30MPH but I have a smaller and lighter boat than yours.

If it is really going 30mph at 3000 RPM, then either a drive with a low gear ratio is installed or there's a really large pitch prop on there.

Boat speedometers are not real accurate either...

 

[coastalcruiser]

Re: Boat won't go fast.

Orininaly posted By Don S.
Engine Won't Reach Operating RPM. Check
My addition*Check for trailer still attached to boat
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.
__________________

 

[erock270]

Re: Boat won't go fast.

Thnks for all your help. I put new plugs and new plug wires on it and now I am turnning close to 4000 rpms and I am going to replace the cap and button and other things to see if it wil perform even better.

 

[allcav]

Re: Boat won't go fast.

I have a 4 cylinder volvo-penta aq130c with a 270 outdrive and my boat is only 17'. it only goes 15 miles per hour at 3200 rpms and that is peek. it can rev in nutrual over 5k rpms but under load only 3200. my prop size 14 3/8 17. I had it at a machanic and he said everything is at spec. Do i need a different prop?. its a 1971.

 

[180shabah]

Re: Boat won't go fast.

allcav - first, let me say welcome to iboats.

You need to start a new thread for YOUR problem, but first check out the DIY and adults only stickies at the top of the forum.

...and STOP reving to 5k in neutral, it doesn't provide any useful data and is really bad for the engine.