Engines and gear ratios

[Mike Haley]

I bought a 96' celebrity 190 br new in 97'. When I picked up the boat the marina had just put a new 97' 205hp 4.3l merc engine in because the 180hp 4.3l engine that was in the boat froze in the winter and cracked. The boat originally had a 19 pitch prop on it, and would hit the rev limiter at half throttle. The marina put a 21 pitch prop on and it hit the rev limiter at 3/4 throttle. So they went to a 23 pitch prop which kept me out of the rev limiter, but took away my hole shot. I've recently put a s/s prop on and had it reworked to try and improve my hole shot with no luck. I was wondering if the gear ratio could be the problem. The ratio is 1.81:1. Anybody have any suggestions?

 

[kev_79]

Re: Engines and gear ratios

sounds kinda weird, the gear ratio sounds right. How fast are you going, and what rpm is the rev limiter kicking in? 5000 rpms with a 23 pitch prop should run about 50-55+. Usually, if you can run at the upper limit on your rpm range, the prop that does that will also have the best hole shot you can get without overrevving. Unfortunately, you only get one gear to run it, so if you want hole shot, you have to sacrafice top end, and vice versa. Let me know what you find and good luck

 

[ODDD1]

Re: Engines and gear ratios

mIKE, THE REASON MANUFACTURERS change gear ratios is to keep the different boats and power packages in the middle of the range of props they manufacture....mddle of range [and effiency] on mercruisers is around the 19 pitch....you should have a 1.50 to 1 ratio drive on that motor, unless your goin up in the mountains with it.....what you have will work, but you need a ventilated prop, that will slip on takeoff....get the marina to 'help' you with the prop selection...