New Boat Problem - Need Advice

markwadd · #1 May 30th, 2002, 09:32 PM

Just bought a new boat and it doesn't seem to be going as fast as it should. It's a rinker 232 (23ft) with 350MAG Bravo 3 and only hits 43mph at 4400rpm. The prop is a 28 pitch. Dealer says that it should do 55-60 easily, but does not know what is wrong. Dealer recommends waiting for 10+ more hours and see if it gets better.

What should I do?... Mark

FlyBoyMark · #2 May 31st, 2002, 03:14 AM

Mark,

Your present configuration is showing that your theoretical speed would be 58 MPH with your present prop. So running at about 90% effeciency, 52 mph....I think your not trimming the outdrive up properly when under way. In additon, I THINK, you might be overproped 2" of pitch, but, that really depends on the weight of the boat. Your running about 200 RPM BELOW the recommended envelope of 4600-5000 RPM. ONCED trimmed properly you might pick up the needed RPM and speed. Even after breakin, another 200 rpm or so is not going to get you 55 MPH at your present configuration. Try trimming the boat with the out drive underway. If the bow is trimmed way down it will slow you down considerably. On another thought..are you loading the boat up with a ton of people and gear when you went out? Are they all sitting in/on the bow somwhere? This is all based on th standard lower unit ratio of 2.0:1 on your Bravo unit. Is this the correct ratio or is it the optional 1.81:1 or optional HIGH ALTITUDE 2.2:1?

markwadd · #3 May 31st, 2002, 06:24 AM

I have tried to trim the boat out of the water and that is when I get the better RPM (4400). The boat is approximately 4200# and the ratio is 2.2, and it doesn't get anywhere near 50mph. This is with a full tank of gas and 2 people on board. I talked to a friend that has the same boat but with a 5.7 engine and he gets 53mph (gps).

Thanks for the help... puzzled... Mark

FlyBoyMark · #4 May 31st, 2002, 03:03 PM

You should be doing about 45-47 MPH with the gear ratio of 2.2 and 4400 RPM that your puting out based on 90% effecientcy.

Why on earth is the 2.2 high altitude ratiio in your lower unit?! Very ineffecient for higher speeds.

@ 4600 RPM, after breakin, 48-50 MPH What ratio and prop pitch does your buddy have on his boat?

FlyBoyMark · #5 May 31st, 2002, 03:09 PM

Just checked Mercury charts, 54 MPH is all your supposed to get out of it @ WOT unless you prop just for top speed.