Prop Selection and poor performance.

[bobstoy]

Recently purchased a 2005 Glastron with 4.3 Volvo. First test drive had poor performance. Tuned it up and was better. Original specs lists a 14 1/2 x 19 prop. I had a 23 pitch, so i changed to a 21 that came with boat. Now it runs better, but still only 35 mph at 3500 rpm. Checked with GPS .Specs state this boat should go 50 mph. Doesnt seem that a 19 pitch would help that.

 

[alldodge]

Assuming a 1.5 ratio drive, 3500 rpm and 35 mph = 24% slip

with a 19 pitch, 4600 rpm and 10% slip it should get 50 mph (49.66)

The issue is, going from 3500 to 4600 should not happen with a change of 2 degrees of pitch. The 50 mph is the same boat with a 5.7 motor. You do need to get the WOT rpm up. Also get a hand held tachometer to check your in dash one. The tach's can be off

 

[Scott Danforth]

make sure your firing all 6 cylinders and you didnt drop a shutter down the y-pipe as well.

23P way too much for a 4.3

 

[bobstoy]

The plugs i removed all looked good, changed as they were original with red over spray. Also changed cap and rotor, and fuel filter. The engine is running smooth. Just think a 4.3 would have more power. I confirmed tach with a hand held. Speed was checked against GPS. Glastron specs show the 4.3 should hit 50 mph. Have no idea what dropping a shutter down the Y-pipe means

 

[alldodge]

confirmed tach with a hand held

Then you have a very weak motor or your boat is water logged. The boat is real light and you should be turning more then 3500 rpm at WOT. Which also means you probably do have 24% slip which is as bad as a heavy cruiser

If you can find out what your drive ratio is, then the numbers could change some, but so long as your only getting 3500, it won't help much

Shouldn't have a shutters with a VP

 

[bobstoy]

The boat came with a new Turning Point 21 pitch prop. They will exchange it for a $25 charge. So i will start with the size recommended by Glastron 19 and go from there. Thanks for the help.

 

[bobstoy]

UPDATE, i installed 19 pitch prop and took for a ride. The difference was amazing. It now comes out of the water like a rocket. I can hit 50 MPH at 4300 RPM. Very happy