Speed and RPM issue

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DHChapGuy

New member
I just purchased a 2018 287SSX Chap with the 8.2 Mercruiser (380HP) engine. Having issues with top speed and RPMs. This boat is supposed to go 48-50 mph and reach 4,800-5,000 rpms per several reviews. I cant get it above 36 mph or 4,000 rpms. Right now it does have a pretty dirty bottom in the rear because it was kept in the water. Previous owner pulled it out monthly and cleaned bottom but could not get to area under trailer. Plugs were changed about a year ago. It seems to run well, just slow. :) Would the dirty bottom impact this much. I will get it cleaned up soon because I will keep it at very clean Dale Hollow lake on a lift. Looking for ideas from this group. Thanks.
 
May need a different prop. You want to achieve WOT as speced. These engines do not like to be lugged....
 
I will check into that after i get the junk off bottom if that doesnt help. It supposedly still has OEM prop. Thanks
 
Are you an experienced boater? Are you trimming the boat properly? Prop pitch, condition could also be a factor, verify they are proper and the engine in good tune along with cleaning the bottom then report back... lots of questions that need answering...

here's some reference of what the baaot should run:

 
Yes. Been boating for 20+ years and definitely trimmed properly. I still need to have prop checked and get the bottom cleaned. Engine was tuned in Aug 2021 per invoice seller shared with me. but still planning on having my guy check as well.

I have seen that video as well and that's the expectation.

Thanks.
 
DHChapGuy said:
I will check into that after i get the junk off bottom if that doesnt help. It supposedly still has OEM prop. Thanks
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Clean bottom is critical. My 8.1 HO will bounce off the rev limiter on a perfect day with lite fuel load and just me aboard.
 
I periodically give the hull a little scrubbing once in a while to keep growth from overtaking the boat. My outdrive faces the sun every day and it doesn't take long for growth to take place even though its been treated.

After the acid cleaning, did you put some kind of treatment on the hull? Although if you're not in a slip it may not be needed.
 
SST said:
I periodically give the hull a little scrubbing once in a while to keep growth from overtaking the boat. My outdrive faces the sun every day and it doesn't take long for growth to take place even though its been treated.

After the acid cleaning, did you put some kind of treatment on the hull? Although if you're not in a slip it may not be needed.
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Haven’t picked boat up yet but they were waxing it after the acid cleaning. And it will be in a slip on a lift from now on.
 
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