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350 Mag MPI, Bravo I best prop for MPH
- Thread starter 40Coupe
- Start date
I've got some more playing to do. With only 4600 RPM with the 21, there is a lot more testing to get it up near 5000 for the best MPH. I'm still thinking it's got some MPH left in it. I wasn't running in the best air or lake quality today. It was 73 and soupy and the lake a little choppy when I tested. If I can get it on glass in some low density altitude, dry, high pressure air I think the little 350 will wake up, especially once I settle on the best prop.
I hear ya! I did find that the boat engine had a slight miss at higher RPM. I came home and cleaned out the corrosion from the distributor cap and rotor. Back out today to the lake to play a bit.
I'd love nothing better than to throw a Whipple on it! Maybe if I win the lottery I can do that!
Update: today it hit 54.0 MPH @ 4500. This was with 600 additional lbs of passengers and no bow cover. Interestingly enough, with all the weight in the far rear of the boat it let me trim it up further and was on the verge of blowing the prop out when it topped out at 54. We also had the Corsa exhaust open as we ripped across the lake. 
More testing today since I had the day off. All runs were with the bow cover on and the Corsa exhaust open. I tried some exhaust open/closed loops and it appears the exhaust open is worth between .5 and 1. As a note, the lake I tested on today has an elevation of 600 feet which is 300 feet lower than the lake that previous tests were run on.
Solas 19p x 15: 4900 RPM 54.25 MPH
Mirage 21p: 4600 RPM, 54.25 MPH (not the Mirage+ but just a base Mirage)
Laser II 19p: 5000 RPM, 53 MPH
Then went back to the Torrent 21p x 14.625 and hit 56 MPH @ 4600!
It looks like what I need at this point is to take the Torrent and pitch it down to 20 and have it labbed. The boat really likes this bow lifting prop!
I could also try a 19P Torrent out of the box. That's an option I may explore.
I also wonder what improved weather would do for the little 350. The DA today was at least 3000 feet. If I can get on the lake in the early morning in early November, there is a chance for some 1000 foot DA or less.
Solas 19p x 15: 4900 RPM 54.25 MPH
Mirage 21p: 4600 RPM, 54.25 MPH (not the Mirage+ but just a base Mirage)
Laser II 19p: 5000 RPM, 53 MPH
Then went back to the Torrent 21p x 14.625 and hit 56 MPH @ 4600!
It looks like what I need at this point is to take the Torrent and pitch it down to 20 and have it labbed. The boat really likes this bow lifting prop!
I could also try a 19P Torrent out of the box. That's an option I may explore.
I also wonder what improved weather would do for the little 350. The DA today was at least 3000 feet. If I can get on the lake in the early morning in early November, there is a chance for some 1000 foot DA or less.
Mark
Well-known member
Well, you are getting there. That motor will run a bit faster in cold weather and a bit slower in hot humid weather. The 21p Torrent/Tempest will likely be your fastest prop. I doubt you will get more speed out of a 19p Torrent. My guess is similar speed, more revs. Personally I would not obsess about the last 1 or 2 MPH unless you spend a lot of time at WOT. Pick a prop that is quick out of the hole, handles great and feels good at the speed you drive everyday.
After I did all the prop testing on my Interceptor I realized I never really ran it WOT. I spend 90% of my time between 3500 and 4000 RPM on long cruises down the lake. So I picked a prop that did that best. I do all my water sports with my Checkmate Diplomat which I propped with a 4 blade for holeshot and skiing.
Keep your eye open for a 20p Enertia. Still think it could be a winner.
After I did all the prop testing on my Interceptor I realized I never really ran it WOT. I spend 90% of my time between 3500 and 4000 RPM on long cruises down the lake. So I picked a prop that did that best. I do all my water sports with my Checkmate Diplomat which I propped with a 4 blade for holeshot and skiing.
Keep your eye open for a 20p Enertia. Still think it could be a winner.
Nothing about chainsaws or tie downs?
More testing today and I couldn't be happier.
19p Tempest +: 54.25 MPH @ 5000 RPM
20p Enertia (13.8" dia): 57.6 MPH @ 4900-4950 RPM
The boat loved the smaller diameter prop. With it trimmed as high as the drive goes, it flat out hauled! The bite was excellent in turns and gets out of the hole like nobody's business. It's a keeper!
19p Tempest +: 54.25 MPH @ 5000 RPM
20p Enertia (13.8" dia): 57.6 MPH @ 4900-4950 RPM
The boat loved the smaller diameter prop. With it trimmed as high as the drive goes, it flat out hauled! The bite was excellent in turns and gets out of the hole like nobody's business. It's a keeper!
