Need Help!! 22' Scarab with 280Merc with Planing Issue

Hello everyone!! This is my second attempt to post here for my first time. I lost my first post... My fault. This one might be a little shorter.

I just bought a (new to me) 1995 22' Scarab, 280 Merc (Carb) with Alpha Drive. When I test drove it we had two people (400lbs) and 20 gals of fuel (146lbs) with no gear and it ran great. Planed right away and jumped up to 4800RPM at about 55-58MPH (according to the speedo, not GPS)

Took friends to lake yesterday (it was 84 degrees here in Arizona) to show of my new boat! Was embarassing. We had 5 people (about 900 lbs), Full fuel (60 gals = 430 lbs) and gear (maybe 150lbs). The boat took 20+ seconds to plane out. I had the drive down and trimmed all the way down. WOT it was running 4000+ RPM.

It felt like it had BITE on the water up until 3800RPM and then felt like it was "spinning out" (like car would do if it was "peeling out") After 20 second of struggling to get on plane it planed out a shot up to 55MPH at 4800RPM.

The prop is a 4 blade Stainless prop. Not sure of the pitch. I will take picks of the prop and post.

Anyone have any ideas of what I should do??? I want to be able to have 4-5 people in the boat and be able to pull skier / get on plane quicker!!

Thank you for the help in advance!! CS

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Hey fellow az boater. What lake did you go to.

I'm buy no means a Expert of 1yr boat owner but could your prop hub be spun out.

Info about spun probs. This happen to me when I hit a log at Canyon.

http://www.marineenginedigest.com/diy/spunprophub.htm

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Check the prop for a spun hub, for sure. Also check for anything in front of the prop that could be messing up the water flowing to the prop. (Like a transducer or something)
If the prop has any blade damage, that should be addressed too.
Where were the people sitting in the boat?

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

I had the same problem, most likely the prop is wrong pitch/diameter for what you want to do with your boat. if you don't know the pitch take it to a prop shop. They can tell you what size to go to. When you get a different prop your boat might be slower but you can have 4-5 peoplee on the boat. This is why it is good to have a few props so you can change them based on what your doing.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

chris50smith said:

The boat took 20+ seconds to plane out. I had the drive down and trimmed all the way down. WOT it was running 4000+ RPM.

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Trimming down/in is fine for getting the boat on plane, partuicularly with a big load aboard.. Once you start to plane, though, you need to trim UP/OUT. That could easily explain why you couldn't hit top speed or come close to WOT rpm.

My .02

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Lake Pleasant. I will check into this. I am sure I will need to take to a Marine shop to check this. I see the posts on how to do it myself, but I need to get a couple other things checked out too.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

It's a simple two buckets and bench setup... so we were all in the back of the boat. 2 in the bucket seats and 3 on the rear bench

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

iconracing said:

I had the same problem, most likely the prop is wrong pitch/diameter for what you want to do with your boat. if you don't know the pitch take it to a prop shop. They can tell you what size to go to. When you get a different prop your boat might be slower but you can have 4-5 peoplee on the boat. This is why it is good to have a few props so you can change them based on what your doing.

Click to expand...

Yes, I think I am going to do that. Take to a Marine Mechanic and see about getting a couple props to try out. I hear they will let you test them. Hopefully they will lead me the right direction. I just want to make sure I am a little educated before going in there.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

JoLin said:

Trimming down/in is fine for getting the boat on plane, partuicularly with a big load aboard.. Once you start to plane, though, you need to trim UP/OUT. That could easily explain why you couldn't hit top speed or come close to WOT rpm.

My .02

Click to expand...

As soon as I feel it going to plane, I start to trim up, that is why I am able to get to 50+MPH pretty quickly.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

TilliamWe said:

Check the prop for a spun hub, for sure. Also check for anything in front of the prop that could be messing up the water flowing to the prop. (Like a transducer or something)
If the prop has any blade damage, that should be addressed too.
Where were the people sitting in the boat?

Click to expand...

Yes, there is a transducer directly in front of the prop. It was installed for the last owners Garmin. Could this really be a culprit?

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Sorry off topic but how was the boating traffic at Pleasant.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

chris50smith said:

Yes, there is a transducer directly in front of the prop. It was installed for the last owners Garmin. Could this really be a culprit?

Click to expand...

Coupled with three people on the back bench, yes. It might "aerate" the water before it goes over the prop, causing it to feel/sound/act like it's "blowing out". It might not be any one thing, but all things added together. Take it out again with a light load, check for a spun prop hub, then put a heavy load in it, and see how it does.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

TilliamWe said:

Coupled with three people on the back bench, yes. It might "aerate" the water before it goes over the prop, causing it to feel/sound/act like it's "blowing out". It might not be any one thing, but all things added together. Take it out again with a light load, check for a spun prop hub, then put a heavy load in it, and see how it does.

Click to expand...

I am going to take it to a Boat Mechanic here in Phoenix and have him check all of these things. Will check out the pitch too, maybe get a second prop for bigger loads. I went out and looked at the transducer and it is located behind the prop, but slightly above the bottom plane of the boat. I am not sure if it is able to cause the issue you are talking about, but since I am not suing that transducer, I think I will remove it and see how it does. Thanks Everyone! I will return and report in a couple weeks.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

There should be numbers on the barrel of the prop or under the prop nut.
It's very likely you have a prop that creates bow lift,good for speed but not for hole shot.
Transducer could be a problem. It isn't likely you have a spun hub thet are generally all or nothing.Once it begins to spin its allmost like a sheared drive pin and won't stop slipping till you reduce throttle and it will very likely do it again as soon as you reach that power range.As time goes by it will become worse and worse till you have to go no wake speed.
Its not unusual for a fully loaded boat to need to have people move forward to get on plane
then they can settle back and relax.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

steelespike said:

There should be numbers on the barrel of the prop or under the prop nut.
It's very likely you have a prop that creates bow lift,good for speed but not for hole shot.
Transducer could be a problem. It isn't likely you have a spun hub thet are generally all or nothing.Once it begins to spin its allmost like a sheared drive pin and won't stop slipping till you reduce throttle and it will very likely do it again as soon as you reach that power range.As time goes by it will become worse and worse till you have to go no wake speed.
Its not unusual for a fully loaded boat to need to have people move forward to get on plane
then they can settle back and relax.

Click to expand...

Great points. I appreciate them. I will see what the mechanic says and go from there, but I glad I received some good recommendations. I really don't think it is a spun hub, since I seem to have full power once on plane, even when I slow down and then gun it, pulling a tube and such. The seating on the scarab really sits far back on the boat... so maybe that is the issue. Just stinks when I go with my other friends boats and they are 1-2 minutes in front of me cause they got the hole shot. They are running 454 and 502 motors in 24-26' boats and run right around 60-65MPH. I was hoping I could get a jump on them when going for a run...but still want to have all my upper range speed too while having a economical 280 MERC, vs a gas guzzling 502. Thanks again!!

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Your probably going to have to get some trim tabs.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

The transducer in front of the prop will be a problem, so will everyone in the back of the boat. 4 blade props are usually best for hole shots, but could be wrong pitch. Don't know what the PO (previous owner) may have told you...The only people who lie more than a fisherman about the one that got away are people trying to sell you their boat.

TO: azboatdreamer, not gonna move there, but our concession trailer just got bought (out of Madera, near fresno) by ppl there.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

Check the other things, and I second the tabs.

With the extra weight it will take a little longer to get on plane..and I have the same cavitation issue if I trim out TOO far.. The tabs will help with getting you on plane sooner if there aren't other issues, like spun hub, or previous owner changed the prop before he turned the boat over to you..not that I would think someone would do that if they were selling the boat but I have seen it happen.

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

NSBCraig said:

Your probably going to have to get some trim tabs.

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My last boat had trim tabs. I loved them. Needed them too since we had a 502. Anyone have any idea where to find trim tabs for an economical price?

Re: Need Help!! 22' Scarab with 280Merc with Planing Issue

cr2k said:

The transducer in front of the prop will be a problem, so will everyone in the back of the boat. 4 blade props are usually best for hole shots, but could be wrong pitch. Don't know what the PO (previous owner) may have told you...The only people who lie more than a fisherman about the one that got away are people trying to sell you their boat.

TO: azboatdreamer, not gonna move there, but our concession trailer just got bought (out of Madera, near fresno) by ppl there.

Click to expand...

I am going to remove the transducer. I am not using it anyway. Going to take the boat into the Marine shop here and get fluids changed, impeller replaced and have them check for a possible spun hub / maybe get a second prop. The one on the boat is a 4 blade prop and is stainless steel. Has a few nicks from hitting rocks though. Not bad, but noticable.