What are your current prop specs? Is it the same as the original specifications?

 

I don’t know what the specs are. It’s usually stamped on the prop right?

 

correct.

 

Gotta load her up to your typical cruising weight, get a nice calm day, and run up to WOT to see what the motor will turn. Double check your specs, but the SBC’s are usually 4400-4800. If you’re in that range, you’re good. If it’s low, make sure the bottom is clean first, then talk to a prop shop to pick up the extra revs through reworking your prop or trying different ones.

 

That's a lot of weight in a 21ft IO boat with 5.0 liter alpha1. Five 150lb adults are a lot different than 5 250lb adults. With 2 adults and full fuel do you reach 4500-4600 rpm? If not then you may be over propped. That boat would act totally different with a 5.7 and bravo1 drive. You may be expecting too much from the 5.0 alpha.

 

Im thinking she was weighed down. The 5 adults are around 200lbs each, full tank of gas and water, gear, bait tank.

I’ve had her out with only my dad and son but never had the opportunity to open her up. I’ll try to the pitch on the prop later today.

I know these boats came from the factory with 6 cyclinder motors. If the 5.0 is struggles, I couldn’t imagine the 6 cylinder.

 

I had a 4.3 MPI 220 HP in a 20’ Crownline 206LS.

With 5-6 people aboard, it wouldn’t plane unless 1 or 2 were in the bow seats.

It ran well with 3-4 people in calmer waters but was a chore in choppy water and constantly losing plane.

 

You need to be able to reach the spec'd WOT for your engine. Go to a Merc Web site, look it up and write down that number. Then, as someone suggested earlier, see what the boat will achieve with full fuel, a "normal amount" of gear, and a proper state of tune. The boat should achieve that WOT. If it does not, you are overloading the engine and need to reprop to achieve the number.

 

All the prop says is 4893272. And AA15P

 

Doesn't get much lower than a 15. You probably have other issues

Bent prop
growth on hull
Motor getting tired
Overloaded cargo

 

Sounds like your engine is not making full power.
When was your fuel filter last changed?
May also want to confirm throttle linkage is fully advancing.

 

We used to have a 19 footer with a 3.0 liter 4 banger and a 19P prop, and that boat would easily plane with as many as 8 people aboard. I would expect that a 5.0 on a 21 footer would OVER-rev with a small 15P prop.

I'm surprised that no one suggested that you may have a spun prop. But more than likely on a boat as old as yours, (and of course not knowing the mode of storage over the past 34 years), I would guess the hull is waterlogged. Take her on a trailer to a truck scale and get her weighed.

 

I have a little update. I think I was overloaded that day. We finally took her out Sunday, beautiful day btw. Just a day out on the water with the family. Four adults and two kids. No bait tank, coolers, gear.

The boat at half throttle would plane right away at 15-20 mph. Didn’t even try to go more on the throttle because it would of been too fast for the kids.

Thank you all. Learning a lot here. Cheers.

 

Read the loading plaque for your boat and then calculate the weight you had onboard when you experienced planning problems.

 

View attachment 66697 Read the loading plaque for your boat and then calculate the weight you had onboard when you experienced planning problems.

My boat doesn’t have the plaque. Previous owner lost it when he redid the upholstery and helm.

 

Searay is still in bizness. A simple telephone call to their customer service could tell you what you need to know.

Seville was SeaRay's budget model, built to compete with the Bayliners of the era. That boat would have come with a 130 HP 4 cylinder mercruiser. The 5.0 was an upgrade. The dry boat weight is about 2300 pounds. The package weight should be in the 4000 pound range. The data is easily googlable.

That boat should over-rev with a 15p prop. A MAJOR engine or hull problem is lurking.

 

I'm looking at the specs on the boat ( Seville Mid Cabin) and it says dry weight is 3289lbs and came with the standard 165hp inline 6 cylinder.

 

I only spent about 1 minute to do a google search and I posted what came up. My weight was the bare hull, yours included the engine as well, so it looks like both numbers are in the same ballpark. It listed 3 engine options - 130, 175 and 205 HP.

I collect boat literature. Back in 1984 we looked at a Seville as a possible purchase. The funny thing is this Winter I went thru boxes and boxes of catalogs and tossed most into the recycle bin. I'm quite certain I had a Seville book, but not any more...LOL.

 

One minute google search turns up a manual with the loading plaque. 8 persons or 1200 pounds. 1400 pounds with gear is the maximum design load. Info is out there from SR which does a pretty good job with product info.

 

View attachment 66713 One minute google search turns up a manual with the loading plaque. 8 persons or 1200 pounds. 1400 pounds with gear is the maximum design load. Info is out there from SR which does a pretty good job with product info.

thank you