micmor64
Seaman Apprentice
- Joined
- Dec 9, 2015
- Messages
- 46
The outboard is a new 1999 9.9 High Thrust Yamaha. The boat is a 26' St. Pierre Dory displacement hull with a displacement of roughly 3600 lbs. The prop is a factory 11 3/4 x 9. At 850/900rpm my gps shows 3.5 mph and I am attaining hull speed at a measured 1950 rpm and wot at 2200 rpm.
At the recommendation of my local Yamaha dealer I tried to increase the wot to 4K plus rpm. To do that, I purchased a Solas Anita 10x5. My speed dropped to just over 2mph at idle, hull speed was reached at just over 2150 rpm and wot increased to just over 2600 rpm. RPM is being measured with a Tiny Tach.
Question: Will operating this outboard at a low rpm hurt the motor overall? I did not like the performance of the Solas prop, I do like the factory Yamaha prop but don't like the 3.5 mph at idle. I am considering a Yamaha 11 3/4 x 7 but am afraid of running the engine at such low rpm under load.
I realize as I try to figure out my prop options I should probably be in that forum, but for now, am I going to hurt the engine running it at these speeds, ( my local dealer says not to do this but can't tell me what harm I'm doing). Any suggestions/recommendations.
Thanks,
Mike
At the recommendation of my local Yamaha dealer I tried to increase the wot to 4K plus rpm. To do that, I purchased a Solas Anita 10x5. My speed dropped to just over 2mph at idle, hull speed was reached at just over 2150 rpm and wot increased to just over 2600 rpm. RPM is being measured with a Tiny Tach.
Question: Will operating this outboard at a low rpm hurt the motor overall? I did not like the performance of the Solas prop, I do like the factory Yamaha prop but don't like the 3.5 mph at idle. I am considering a Yamaha 11 3/4 x 7 but am afraid of running the engine at such low rpm under load.
I realize as I try to figure out my prop options I should probably be in that forum, but for now, am I going to hurt the engine running it at these speeds, ( my local dealer says not to do this but can't tell me what harm I'm doing). Any suggestions/recommendations.
Thanks,
Mike