Low RPM at WOT

[TimTJR]

Hello friends,
I recently purchased a 2011 Stingray 208LR with a Volvo Penta GXi 4.3. The long block was replaced before I bought it so now it only has about 20 hours on it. I do have documentation of the new engine. It has a 14-3/4 x 19 ss prop. With me by myself, I can only get the boat up to 45 mph at 4000 RPMs at WOT and trimmed out. (going by my analogue tach on the dash). This engine should get between 4400 and 4800 RPMs and should go a hair over 50 mph. It always starts right up and the engine always runs and idles smooth. Never idles rough, never hard to start. No indications of needing a tune up. I also have a depth finder with a speedometer and it matches the analogue speedometer on my dash within a few mph. It always shifts into gear smoothly. I can't find anything wrong. Does anyone have any ideas? Should I go down to a 17 pitch prop? Thanks in advance for any help.

 

[Scott06]

Hello friends,
I recently purchased a 2011 Stingray 208LR with a Volvo Penta GXi 4.3. The long block was replaced before I bought it so now it only has about 20 hours on it. I do have documentation of the new engine. It has a 14-3/4 x 19 ss prop. With me by myself, I can only get the boat up to 45 mph at 4000 RPMs at WOT and trimmed out. (going by my analogue tach on the dash). This engine should get between 4400 and 4800 RPMs and should go a hair over 50 mph. It always starts right up and the engine always runs and idles smooth. Never idles rough, never hard to start. No indications of needing a tune up. I also have a depth finder with a speedometer and it matches the analogue speedometer on my dash within a few mph. It always shifts into gear smoothly. I can't find anything wrong. Does anyone have any ideas? Should I go down to a 17 pitch prop? Thanks in advance for any help.

Id verify the tach is working corrcectly and was speed by GPS or the dash guage (which are like +/- 8 mph ) ? If you are indeed higgit 45 in that rig I bet your tach is off. I wouldnt buy anything until you verify the numbers

 

[Chris1956]

50MPH with a 4.3L in a 20 footer is very unusual. Good luck with that.

 

[Stinnett21]

Stingray's are typically fast hulls too. You're 700 rpms short for some reason and I wouldn't think a 19" would be that far off. Something is not right. I hate to ask but how was the boat stored? You could have soaked foam.

 

[Texasmark]

Co worker had a deep V, closed bow, SR 18' 165 I6 I/O back in the late '60s. I had it to 45 with 3 aboard while he was getting the trailer. At first he was mad at me for making a run while he was getting the trailer but later apologized and thanked me for letting him see his boat perform. The lifting strakes on the deep V lifted the hull out of the water and there wasn't a lot of boat in the water at the time. Don't recall anything other than the speed.

 

[TimTJR]

Id verify the tach is working corrcectly and was speed by GPS or the dash guage (which are like +/- 8 mph ) ? If you are indeed higgit 45 in that rig I bet your tach is off. I wouldnt buy anything until you verify the numbers

Dash guage reads 45 mph while the depth finder reads 40 mph. I used my hand held tach today and the RPMs are accurate.

 

[TimTJR]

Stingray's are typically fast hulls too. You're 700 rpms short for some reason and I wouldn't think a 19" would be that far off. Something is not right. I hate to ask but how was the boat stored? You could have soaked foam.

The boat was stored in indoor garage storage.

 

[TimTJR]

50MPH with a 4.3L in a 20 footer is very unusual. Good luck with that.

The boat is 20' 8" long. I been doing a lot of reading and researching and there are people who claim to get 52 mph at 4800 rpm. I can't get mine to go over 4000 rpm

 

[Chris1956]

My 18 foot SeaRay 205HP 4.3LX would do about 42MPH at 4400RPM. It had a pretty good hull. I don't think a SBC V8 would have pushed it to 50MPH.

Your speed may vary.....

 

[dan02gt]

I owned the 19' version (the 198LX) with the 220 HP MerCruiser MPI and a Alpha 1. I ran a 20P 3 blade Enertia and it would run 54-55 MPH on the GPS at ~4700 RPMs. There is no reason the 208LR shouldn't run low 50s if that engine is running right.

 

[QBhoy]

50MPH with a 4.3L in a 20 footer is very unusual. Good luck with that.

Perfectly normal to see 50 gps from a fast hull like this and an mpi 4.3. As long as she’s well propped. As an example, Every regal 1900 with this engine I know of, will easily do 50 gps. One particular well propped one, with a 19” tempest plus…will touch 53 mph. A stingray should manage too, I’d think. Something else is going on here.