Which Props would work best?

[adamk523]

I have a 1996 Larson Cabrio 280 with Twin Merc 4.3. I am running 17P Mercury SS Vengeance Props. My Hole Shot is terrible. The boat Cavitates for a few seconds, My RPMS Rev to almost 5000 RPMS and eventually comes on plane and the RPMS come down. I was told by a Larson dealer that this is due to the Delta Conic Hull design. Once planing, you need to keep the boat at a minimum of 3600 RPMS to stay on plane. At 3600 RPMS the boat only cruises at about 21 MPH. My WOT is 4800 RPMS. The boat does about 39 MPH at 4800 RPMS. I tried my friends 21P 13 3/4 props, and my Hole shot, and cruise speed improved, but my WOT was only around 4000 RPMS and top speed was about 30 MPH. Based on this, I bought a set of 19P by 14" props. This did not seem to be much better than the 17P and my top speed was still only 32 MPH. Any suggestions? The boat runs great at 4000 RPMS, but burns lots of gas. I don't understand the advantage of this hull design unless your running at full throttle all of the time.

 

[walleyehed]

Re: Which Props would work best?

What props did you buy to replace the Vengeance props with? What Model and material?

 

[Crownie2]

Re: Which Props would work best?

Somethings not right here.

Did you buy it used?

Has it always performed this way?

 

[adamk523]

Re: Which Props would work best?

Somethings not right here.

Did you buy it used?

Has it always performed this way?

Always performed this way. Other people at my marina with similar boats have similar issues. You can't trim the drives when you run the boat. YOu will lose plane instantly. This is normal for this hull design. At 4000 RPMS, the boat runs great. The boat is heavy in the back. I have twin engines and a generator.

 

[adamk523]

Re: Which Props would work best?

What props did you buy to replace the Vengeance props with? What Model and material?

I bought the boat used, but this seems inherent with the delta conic hulls from Larson. Someone at my marina has a 29 larson cabrio with Volvos. He has similar issues. He just put 4 blade aluminum props on. He said it helped slightly with hole shot, but that was about it. The RPMs vary when you turn the boat, and when the water is rough. The synchronizer is all over the place.

I bought used 19P Stainless props. They were the older style Mercury props (not vengeance) I dont recall the name on them.

 

[walleyehed]

Re: Which Props would work best?

with your hole-shot and mid-range improving with the 21's, I am at a loss. the more the RPM drops at WOT, the slower the hole-shot is normally.
If it's really that heavy in the rear, 4-bld SS may be the way to go...much more cup (bite) and better holding power in turns and rough water.

 

[tommays]

Re: Which Props would work best?

You might ask in the I/O forum also

This has come up there and how close the motors are mounted to each other and the angle of the drives to each other can be and issue as they tend to vent each other causeing the blow out on hole shot


And the twin 4.3 power package is the bare minium for that size boat

Tommays

 

[Crownie2]

Re: Which Props would work best?

I wasn't able to locate this topic elsewhere, but it does sound like an I/O location issue if they props are venting on take off, but act (fairly) normally on plane.

I'm thinking four blade props are worth a try.

Sorry, but I have to ask - did you drive this boat before you bought it?

 

[adamk523]

Re: Which Props would work best?

Drove the boat, but I never drove a twin before I bought it. It handles great at 4000 RPMs. The boat is fast, smooth, and is what you would want, but you have to run it at 4000. I had nothing to compare it to.

 

[Crownie2]

Re: Which Props would work best?

I'd suggest you talk to more owners of this design and dealers about what they did or would suggest...

Also, see if there is any possible way to get some of the weight in the stern moved to the bow area. I'm pretty sure this would help.

Do you have trim tabs? If not, adding electric or hydraulic tabs would probably help too.

Bob

 

[Dhadley]

Re: Which Props would work best?

What's the toe-in set at?