Volvo Penta 5.0GL SX Drive only 45mph max?

[ktmrider]

According to the owner's manual, my Volvo-Penta motor is rated at 300HP (I think it's a lie). C'mon, a 5.0 liter carburated engine putting out 300HP?

Anyway, the most that I was able to do on the water was 45mph according to the gps.

So how does a 5.0 V8 can only do 45mph on water? I was hoping to easily get 50mph.

2000 Crownline 205 CCR.

 

[achris]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

According to the owner's manual, my Volvo-Penta motor is rated at 300HP (I think it's a lie). C'mon, a 5.0 liter carburated engine putting out 300HP?

Anyway, the most that I was able to do on the water was 45mph according to the gps.

So how does a 5.0 V8 can only do 45mph on water? I was hoping to easily get 50mph.

2000 Crownline cuddy cabin ...21 feet.

It's closer to 230hp than 300hp.

45 mph is 39 knots. I'd say in a 21' cuddy that's pretty darn good!

My 20' cuddy has a 4.3MPI, about the same power as your 5.0 carbbed and I do 40 knots (43 with a different prop, light fuel load and only me on board and the right weather)...

Chris........

 

[Senior B]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

My boat is a simular setup: Glastron 205GX / Volvo 5.0 GL/SX. That motor is rated at 220hp. With a light load, 21 pitch prop, 1/2 tank of gas and properly trimmed, I can get 53MPH on GPS. With a load of 6 adults, booze for the day and the 19 pitch prop and I'm down to 45-48mph. What's your RPMs at full throttle?

 

[achris]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

My boat is a simular setup: Glastron 205GX / Volvo 5.0 GL/SX. That motor is rated at 220hp. With a light load, 21 pitch prop, 1/2 tank of gas and properly trimmed, I can get 53MPH on GPS. With a load of 6 adults, booze for the day and the 19 pitch prop and I'm down to 45-48mph. What's your RPMs at full throttle?

The Glastron 205GX is an open bow and considerably lighter than Crownline 205 CCR...

 

[ktmrider]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

You're absolutely right....it's more 230-240hp range.
I think my max rpm at full throttle was 5400rpm.

So changing pitch will affect acceleration and top speed.

So what do I need to do to get it to 50mph with only two people on board and 20 gallons of fuel (half tank)? I believe the current prop is totally stock.

 

[captmello]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

5.0 GL max RPM is 4800. You've got room for more prop and will most likely gain speed.

 

[izoomie]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

I had a 5.0l merc on a 20' edson bowrider. Just me trimmed real nice I could just touch 50mph on the gps. Sadly there are not many places in the detroit river you can go that fast in a small boat like that.

 

[180shabah]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

5400 is over-reving.

 

[PitchFork]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

No if he is over revving at 5400 and needs to get into the RPM range he needs to go UP in prop pitch. Probably 4" from 17" to 21" which means he would lose 600 - 800 RPM, lose top speed, and longer to get out the hole.

I would make sure you have the right prop on it both diameter and pitch.

I have 15 1/4" x 17" and I shoot right out the hole quickly and can reach a top end of 49MPH with just me in the boat with a RPM max of 4600RPM.

From iBoats Prop Section
"Effect of Prop Pitch on RPM (see image 2)
A pitch change can increase or decrease the RPM's and bring RPM's into the recommended range. A 2" increase in pitch (for example, from 21" to 23") typically results in a decrease of approximately 300-400 RPM"

 

[Senior B]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

Stock prop on those 5.0GL with a 1.60 gear ratio SX drive is usually a 19 pitch to get you 4800 rpm at full throttle. Sounds like you have 15 pitch to be turning 5400 RPM. Don't recall reading where you're from, but here in Tidewater VA, my local prop rework place sells used props and will let you test drive one till you find what makes you happy. Might check if you could do the same. If you pull a tube or skis your going to want the spec 4800 max rpm. For me it's a 19 pitch. 21 pitch will max me out @4500 rpm.

 

[hwsiii]

Re: Volvo Penta 5.0GL SX Drive only 45mph max?

ktmrider, what is your prop pitch and lower gear ratio.


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