Interesting Discovery While Propping a New Outboard

A customer brought in his boat for propping after being repowered. Originally equipped with a 2008 Yamaha F225 six-cylinder outboard, the replacement he had installed was the 2019 Yamaha F200 inline four cylinder. The original engine was propped with a 21-pitch Mercury Revolution four-blade and this is what was on the new engine. When we ran this prop on the new engine it delivered a disappointing maximum of only 4000 rpm – 5500 to 6000 rpm is normal when propped correctly.

I estimated the prop had too much pitch for the new F200 LB inline four. We opted for a Yamaha Turbo Offshore I with 17-pitch and reran the trial. The results were still disappointing at only 4200 max rpm. For every inch in pitch reduction we expect a gain of 200 to 250 rpm. Reducing from 21 to 17-pitch should have delivered 800 to 1000 additional rpm.

We verified proper engine operation and boatside fuel system. We spoke with Yamaha and other technical services to discover if we were missing something. The boat was weighed on a certified scale to verify the hull was not waterlogged and overweight.

Our final call for tech advice went to longtime friend Louie Baumann at Baumann Propellers. We brought Louie up to speed and he recommended trying the same Mercury Revolution prop, but with 15-pitch.  According to Louie, the Yamaha Turbo Offshore I has historically been found to be two pitches higher than the markings on the barrel. We tried the Mercury Revolution four-blade with 15 pitch and the boat performed flawlessly.

While propeller diameter and pitch markings may be the same, do not assume the performance will correlate directly between different prop manufacturers. A lesson well learned.

Have a great fall fishing and boating season!

Chris Mapp
Coastal Bend Marine | Port O’Connor, TX | 361-983-4841