I just purchased a 2009 Xpress H18 with Yamaha 115 4-Stroke. I took it out the other day for a spin, just me, about 10 gallons of fuel and 3 batteries.. Running WOT the engine would only turn about 4900 RPMs and top speed was about 39mph. I thought maybe the engine just needed a tune up, since I has sat idle for a few years. I changed fuel filter, plugs, oil and lower unit oil and put fresh gas in the tank and some sea-foam.
I take the boat out again after the above maintenance, this time its me, my brother, 3 batteries, and about 25 gallons of fuel. The boat wouldn't even get on a plane, the engine was maxing out at about 3500 RPMs. It would just plow thru the water with the bow high in the air, I tried adjusting trim, but could not get it up on plane. I had my brother get out, and still the boat would not get on top of the water.
Boat came with a 19 pitch prop, so we put a 15 pitch on there just to test. With the 15 pitch prop, the boat would get on top of the water with both of us, but it did take longer than I think it should, the boat will plow thru the water before finally getting up on top of the water. With the 15 pitch, we could get the engine to about 5700 WOT with an empty livewell, if the livewell was full it would only turn about 5400, max speed at this point is about 34mph.
Basic specs: Xpress H18. Yamaha 115 4-stroke, 6" manual jackplate.
Now to my questions.
1. What should be the normal performance for this boat with a 115? Does anyone here have this same setup and maybe give me an idea of what to expect? How is the hole shot? What is average top speed?
2. If this in an engine issue, what could be the cause? Engine seems to run smooth.
Any help is greatly appreciated. I'm hoping its an engine issue, because if this the normal performance of this boat, I will be greatly disappointed.
Troy