270DA 7.4L single B3 trouble getting on plane

vector4

Member
Jun 24, 2015
59
Baton Rouge
Boat Info
2000 Sundancer 270
Engines
310hp
Just wanted to run this by you guys. Bought the boat last June, it's a 2000 270DA widebody single 7.4L MPI with B3. Boat ran fine, then about 3 months later in Sept had issues. Would start to come up on plane and then just sink back into the water. Almost felt like a spun prop hub, it's just like there was no bite in the water or power to get it up. I could go WOT and do some drastic weight shifting and get it to plane off but to keep cruising speed I really had to give it way too much throttle.

So B3's are solid hub so it's not that, pulled the props (24p) and compared to another set I have, they aren't bent. I thought maybe fuel issue so I change the fuel filter and cleaned the flame arrestor. Engine sounded a lot peppier after that so I was pleased until it did the exact same thing. And it does it from what I can tell at the exact same point each time.

Now... I am bottom painted with ablative paint. I left it in a wet slip all summer and when I pulled it the bottom was covered with 1/4" layer of algae. The lake I had the boat in was tiny and I idled out or maybe cruised for 5-10 min max. So I don't think I ran it enough for the paint to scrub itself off. It started peeling and I scrubbed the top layer with the algae off this winter so the bottom is fresh now.

So I got to thinking maybe that layer of algae was causing this and making the hull drag so much I couldn't get up on plane.

If that's not it my options are plugs, cap and rotor next. Then maybe I have a leaking manifold that's letting water in and killing engine power once I hit 3k+ rpms? Engine idles fine and rev's in neutral fine. I need to pony up for a techmate...

I'll get it figured out but thought I'd see if the story jived with anyone.
 
I will bet you have solved your problem by cleaning the algea from your hull.
 
I'd love for that to be it. This is my first wet slipped boat and my first experience with bottom paint, critters, etc. I'm just not familiar with what it's like when you have junk on the hull.
 
You're right that you don't have prop hubs. But you do have an engine/drive coupler which can cause the same effect as a spun hub. However, the effect those would have is the RPM's jumping higher than what you would expect for a given speed - a lot like all of sudden putting the drive in neutral. Plus, it's very unlikely that you would be able to hold WOT. Another way to think of it is similar to a worn clutch in a car. From what you're describing, this does not sound like your problem.

I agree that it sounds an awful lot like the scum layer is the culprit. You might be surprised at what scum can do... Or at least you would have been surprised before your recent experience!

The best way to keep the scum layer off... Use the boat more!
 
I thought about the drive coupler because I just replaced the coupler on my last boat (a 23' baja) because the stringers sagged and the engine got out of alignment and chewed the splines off. I know that the rubber can spin in that coupler but I figure that if it fails then it fails all or none. I don't smell any burnt rubber smell and like you mentioned I am able to throttle to WOT and stay there until it eventually does get on plane. I'd think if the coupler was slipping then I'd be tearing it up and getting a nice rubber fire back there.

I just moved to South Louisiana so I plan to be able to do a lot more cruising! I also am not going to wet slip the boat until I learn more about the area and what area I am going to boat in the most.
 
Clean bottom first. I had this boat and something similar happen. In the bilge near the fuel tank look for fuel shut off. Mine turned like a outdoor spigot and it had slowly started to close thus not getting enough fuel to the engine.
 
Well guys, finally got the boat out for the first time yesterday. Came right up on plane like normal. So, that was it, that little layer of algae/scum on the bottom. Crazy what a difference that can make!

Thanks for the input guys.
 

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