mswalter2009
Seaman Apprentice
- Joined
- Jul 6, 2009
- Messages
- 45
Hwsiii - You nailed the mph exactly. Thanks so much for your and others help. Anyone reading this -Hwsiii and the other "prop gurus" know that they are talking about. Post your questions and give the information they are asking for. Pictures help.
Question - Do you think I should go up one more hole? You said the 688-45930-02-98 likes a lot of height. If you need I can send some pictures. At this point I'm happy with the performace. However, I still have 4" of throttle (at the remote) with no difference in rpm just a slight diff in engine sound. It seems like there is more. I want to get a picture of the cav plate at different rpms. Just can't safely do that by myself.
For anyone reading this post here's the situation -Just repowered my boat with a new engine (specs below). Worked with the dealer on prop size and I went with a less expensive ss prop by michigan wheel. It was the Apollo Series 13 1/4 by 17 SS prop. First test run was 4500 max rpm at WOT. Compared to the yamaha prop listed below this is massive prop. So much so that the yamaha high clearance anode trim tab did not clear the prop. Started searching this site and Hwsiii consulted. Also contacted the company that rigs Privateers. Both said - the prop you need is the yamaha semi cleaver 688-45930-02-98. Had 8 hours on the engine and kudos to the dealer, they traded me back with only the difference. $74.
Todays Test -
The dealer swapped my the appolo prop (13 1/4 x 17) for the yamaha #688-45930-02-98 (13 x 17) Put in after work and the difference was much much improved.
Boat weight - 1250 dry
Boat -1984 Privateer Retriever 18' center console
Sea Level -level, charleston sc
Boat hull - Bay boat, slight deadrise at stern. no pad
Test weight - 1950, includes engine. One person, some gear, Some boat "sodas" 10 gallons of fuel in center line tank. Ya, I'm a big guy.
Engine height -# 2 hole (was on #1 lowest, raised one hole for this test)
Engine -2008 Yamaha 90 TLR 2 stroke
Gear Ratio: 13:26 (2.00)
Prop -Yamaha #688-45930-02-98 (13 x 17) Black SS, semi clever
Fuel - 25:1 (last hour of break in) 86 octaine
Cav plate - could see cav plate above waterline at 4100 to 4800 rpm. A good bit of spray around cav plate but above waterline nevertheless.
WOT rpm -5200 into the wind, slight chop in waterway, 5300 down wind.
Wind - 13 to 15 knots
Speed -38 mph (gps) (this was done with a chase boat)
Engine trim - just below cavitation. bow lifted nicely. Started to porpoise slightly, lowered engine a couple of ticks, still 5200 / 5300 rpm. So, I coud trim a couple of ticks down per the yamaha digital guage and the rpms stayed the same. More that two / three ticks and the rpms would drop a 100 or so.
Throttle response - Can throttle up to 5200/5300, still have about 4" of throttle left, go to WOT no difference, slight change in engine sound.
Time to plane - dont' have this but I will
Time to 38 mph - don't have this but I will
Question - Do you think I should go up one more hole? You said the 688-45930-02-98 likes a lot of height. If you need I can send some pictures. At this point I'm happy with the performace. However, I still have 4" of throttle (at the remote) with no difference in rpm just a slight diff in engine sound. It seems like there is more. I want to get a picture of the cav plate at different rpms. Just can't safely do that by myself.
For anyone reading this post here's the situation -Just repowered my boat with a new engine (specs below). Worked with the dealer on prop size and I went with a less expensive ss prop by michigan wheel. It was the Apollo Series 13 1/4 by 17 SS prop. First test run was 4500 max rpm at WOT. Compared to the yamaha prop listed below this is massive prop. So much so that the yamaha high clearance anode trim tab did not clear the prop. Started searching this site and Hwsiii consulted. Also contacted the company that rigs Privateers. Both said - the prop you need is the yamaha semi cleaver 688-45930-02-98. Had 8 hours on the engine and kudos to the dealer, they traded me back with only the difference. $74.
Todays Test -
The dealer swapped my the appolo prop (13 1/4 x 17) for the yamaha #688-45930-02-98 (13 x 17) Put in after work and the difference was much much improved.
Boat weight - 1250 dry
Boat -1984 Privateer Retriever 18' center console
Sea Level -level, charleston sc
Boat hull - Bay boat, slight deadrise at stern. no pad
Test weight - 1950, includes engine. One person, some gear, Some boat "sodas" 10 gallons of fuel in center line tank. Ya, I'm a big guy.
Engine height -# 2 hole (was on #1 lowest, raised one hole for this test)
Engine -2008 Yamaha 90 TLR 2 stroke
Gear Ratio: 13:26 (2.00)
Prop -Yamaha #688-45930-02-98 (13 x 17) Black SS, semi clever
Fuel - 25:1 (last hour of break in) 86 octaine
Cav plate - could see cav plate above waterline at 4100 to 4800 rpm. A good bit of spray around cav plate but above waterline nevertheless.
WOT rpm -5200 into the wind, slight chop in waterway, 5300 down wind.
Wind - 13 to 15 knots
Speed -38 mph (gps) (this was done with a chase boat)
Engine trim - just below cavitation. bow lifted nicely. Started to porpoise slightly, lowered engine a couple of ticks, still 5200 / 5300 rpm. So, I coud trim a couple of ticks down per the yamaha digital guage and the rpms stayed the same. More that two / three ticks and the rpms would drop a 100 or so.
Throttle response - Can throttle up to 5200/5300, still have about 4" of throttle left, go to WOT no difference, slight change in engine sound.
Time to plane - dont' have this but I will
Time to 38 mph - don't have this but I will
