Boat will not reach max rpm's
 

I have a 23.5 ft rinker with a 454 mercruiser thunderbolt engine with a bravo 1 out drive. I have a stainless steel 23 pitch prop on it. I just recently rebuild the engine and can't seem to get top speed out of it. I am only getting 3700 Rpm's at WOT. I had the same problem prior to rebuilding the engine. Also I do have a freshly rebuild Rochester quadrajet carb on it. Any ideas?

Try a 21 pitch.

Do you think it can possibly be the ignition? I was mentioned to me that I may not be getting enough spark.

Try a 19 pitch.

several questions, is this a new to you boat and has it always run this way? did it have the carb on it when you got it or did you put it on and then have this problem? what was the reason for the rebuild? there are several things that could be the problem. what speed are you seeing at the 3700? are the secondaries opening on the carb? what is the total timing on the engine? if you can give as much history and info as possible it would help.

The reason for the rebuild was that a cousin of mine some how overheated the engine. When I had originally purchased the boat I then was also only getting 3700 rpms out of it. When rebuilding the engine I had a pro comp cam installed and also port polished the heads an had the carburetor rebuild. I am getting 42 mph measured by GPS @ 3700 rpms. I am not too sure what you mean about additional openings on the carb although it has a Rochester quadrajet carb.

quadrajet has a secondary lockout if the choke is not completely open. the quad works by opening the primary first then the secondary. the secondary opens and the vacuum pulls open the air valve on the top of the secondaries. if the carb still has the lockout on it the secondary valve may not open or there could be a problem with the air valve opening. if there is a problem with the secondary then you will have a very small two barrel and it will not make any power. what is the initial timing and the total timing at around 3500? what do the plugs look like. are they white like it is very lean or running out of fuel? if the carb and timing is ok you may have a fuel supply issue, bad fuel line, anti siphon valve restricting it, etc. if you run low on fuel pressure the motor will lay down and only turn what ever rpm you have fuel for.

Good advice, thanks. I am going to check these components out tomorrow and let you know what the trimming is and what I find.

untie it from the trailer.

Did you buy this boat from a High Performance Parts Salesman from TN ? He had a boat just like it.

Chris, is this you under a new name after being banned ?