WOT max rpm for Yamaha sterndrive with YEMS

[Celeb92]

Hi. I originally posted this question in Props and Silvertip provided a response but suggested I re-post here. Does anyone know what the max rpm should be for a 5.0 SBC with Yamaha YEMS system sterndrive? Silvertip suggested 4400 to 4800 and that seems right for a marine v-8 but can anyone narrow the range or give me an absolute top for this Yamaha? The rig is a 1992. I am trying to collect info so that, come late spring when I can again lead the boat to water, I'll know what to ask you guys and the experts over in the prop area. To the best of my recollection with only about 5 hours experience with this boat before winter set in, the engine was turning 4600 rpm with a 14 x 19 aluminum three blade. The boat is a fairly heavy 21 ft Celebrity bow rider. My speedo showed 48 mph and a friend runnint parallel to me said about 47 on his GPS as I slowly pulled away from him.

 

[Don S]

Re: WOT max rpm for Yamaha sterndrive with YEMS

4400 to 4800 is a normal range for SBC engines form 92. I doubt they were any different for Yamaha's as they were for OMC, Mercruiser, and Volvo of that era.
4800 would be your max rpm at WOT with a well tuned engine, clean bottom, and trimmed properly. Speed is what ever happens and depends on the prop, the manufacturer, type, blades, yada, yada, yada.
Now if you want to tinker with props, head over to the prop forum. http://forums.iboats.com/forumdisplay.php?f=35

 

[Celeb92]

Re: WOT max rpm for Yamaha sterndrive with YEMS

Thanks Don. I don't really know if I have a prop question YET since the boat is so new to me and, when first purchased, had an ignition problem that limited rpm to about 2400 rpm. By the time that was fixed, the season was over and I pulled the boat. Seems if I'm turning 4600 with my current prop, I'm probably OK. I mentioned the speed only to let responders know that the rig seemed to be running reasonably well. As a newbie, I'm reading all the posts (a real learning experience) and asking for info so I can really dig into this boat come the next season.

You guys are great! Thanks for the help.

 

[Capt Ken]

Re: WOT max rpm for Yamaha sterndrive with YEMS

If you get it much over 5000, the computer will kick in the over rev limiter so try to keep it under 4800.