250da Questions is this normal?

[91yellowfellow]

I have a speed boat a 20 ft with a 305 in it and i got this 250 day yesterday. I took it out today with total of 4 adults and there is no spedo but i swear this thing at full throttle is not hitting more then 15 MPH There is a monster wake behind me no matter how much you use the trim tabs or raise or lower the drive nothing works. I know this could maybe me the prop but even so only about 15 mph? I was told the motor was replaced with a brand new 350. When I tore the boat apart i found the cover to the carb and it saids 228 hp thunder bolt.... I am starting to think this boat might only have a 305 in it... Hard to tell from looking as it was dark I will look closer in the daylight... Was a 305 avil that year for the 250da? I am calling the shop that did the motor work tomorrow to ask them as well but this boat should be able to get on a better plane and leave less wake correct? I mean the change in speed from 1200 rpm and 3500 rpm is maybe 5-10 mph maybe..... Opinions?

 

[mwph]

Something isn't right. Does the engine run smoothly? Was the exhaust updated with the new engine? Is 3500 max RPM? Any work done to the outdrive? Do you have access to another prop you could test?

You can check what engines were available for that model on Sea Ray's site but that will just tell you what they put in it back then. If its been repowered its a whole new ballgame.

 

[91yellowfellow]

max rpms are about 4400 and there is no diff in the speed at 3400 or 4400 same thing just huge wake every jet ski was following me today..... I do have a prop on my speed boat but was thinking that would not work well on this boat. I am told its a new 350 with a rebuilt alpha 1 at the time of the repower. I am wandering if its really a 305 and not a 350. I was wandering if its wrong prop but I can get max rpms so i dont know. I dont have a trailer but I can beach it.... Are they hard to change when in the water?

 

[mwph]

Props can be changed in the water but I'm not suggesting you put just any prop on there. If you suspect a prop issue, find someone that can 1.) tell you if what you have now is right for your boat & 2.) tell you if it is damaged in any way.

Again, I'm no mechanic but even the smaller 305 should not yeild the results you have. Either way, I'd get the shop involved. A 1000 rpm increase with no added speed points to bigger issues. In your follow up post you mention a rebuilt drive as well. Lots of gear ratio stuff there which is out of my league.