Porpoise problem
 

Hello everyone, now that I have a few hours behind the wheel of the 1988 240 Sport I have found a problem with the boat porpoising :eek: . I have piloted a few boats over the years but never encountered a problem like this.

The boat starts to porpoise around 3600 rpm and will porpoise until 4600 rpm. You can tuck the drive all the way in and it still porpoises. If you slow down to 3300 rpm or so the porpoise goes away. If you take the boat to 5000 rpm and trim it up the porpoise goes away, it does run loose but the porpoise dose seem to go away.

I have tried a number of different props (both 3 and 4 blades) I found the best prop to be a Bravo 4 blade

Thanks to Julie and Matt at Throttle Up! :drink:

If anyone has something to check or have seen this before please let me know. Your help would be greatly appreciated.

Thanks, Speed

Re: Porpoise problem
 

Very common problem on Baja. I've heard that hook in the hull is one of the reasons for this. The other problem could be the degree of deadrise in your boat. I'd check for hook first and go from there.

Re: Porpoise problem
 

If you dont have tabs you may want to add a set.. :) Jamie / Lakeside

Re: Porpoise problem
 

Actually they put the hook in to keep the boat from porpoising.

If you have ever ran with any of the older Cigs that are true deep vee they ALL porpoise because they do not have a hook.

I removed the hook from my Baja 36 Outlaw and will see a slight porpoise at 3800 to 4000 RPM, but just a small amount of tab takes it right away without any lose of speed.

As mentioned, you NEED tabs if you do not have them.

Re: Porpoise problem
 

Thanks guys, :drink: I do not have tabs on the boat. It sound like I need to move installing a set of trim tabs up on the list of items to install before next season.

I have read some articles on hulls that have a hook designed by the manufacture and it is usually close to the transom I believe. I have also read articles about boat that have a hook for some other reason not intended by the manufacture (sitting on the trailer that was not set up right or something like that) is there a good way to check the hull for the “bad” kind of hook with the boat on the trailer or is this something I need to have a professional check out.

I know the trim tabs might be fix but for piece of mind I would like to check the hull.

Speed

Re: Porpoise problem
 

You will be better served to spend your money on trim tabs that will serve several functions, then on blue printing the hull which will run $2K and up.

Take a straight edge, or carpenters level that is at least four feet long to six feet and place it on the back edge of the hull and run it forward on the bottom of the hull. You will probably see a high spot where the hull does not contact the straight edge. You will see where it starts, where it ends and how deep / high it is. Then go to the other side in the same area and compare. It they are the same then you probably have a standard hook. It the are different from side to side then you may have a hull that is damaged slightly from the trailer.

Most all 23 foot and up boats come with tabs now days. That is a good investment for you.

Good luck

Re: Porpoise problem
 

Dock did you notice any speed improvements from doing it. I know mine has hook, but they are talking around 3k to blueprint a 3' triangle thought that was a little steep. :eek: :eek:

Re: Porpoise problem
 

Dave ..... Welcome over here at OSO!
I'm so glad to have you here to help us defend the brand :evilb:

Re: Porpoise problem
 

I also got a 88 240 sport and it does have a slight porpoise to it also. Its probably just natural for that hull. But I got tabs on it and I use them to smooth out the ride. Havent noticed any loss of speed from the tab use. Like Dock said. Tabs will be the best next step you can make.

Re: Porpoise problem
 

Bill are you saying I post alot regarding Baja's? I'll prolly never post as much as I did over on the other site, but some good people are over here so I figured I'd come hangout instead of lurk. :cool:

Re: Porpoise problem
 

And Dock is here too. :D

I had the same thing with my 25 Outlaw and 33 Outlaw. But the 33 only does it when it is full of fuel. The 25 would do it all the time at mid range with out tab.

Re: Porpoise problem
 

Thanks again,
I will check the hull and probably just add the tabs :D . Any recommendation on what trim tabs to use. I remember seeing a Lenco racing tab in a recent boating magazine that looked good.

Thanks Speed.

Re: Porpoise problem
 

I didn't go fancy. I used Bennett Sport Tabs on my 250.

Re: Porpoise problem
 

If you are going to run in the rough get the k planes 280s or 380s I had the trim tabs bennetts boat came with them in 88 , I broke them off 2 or 3 times in one yr :rolleyes: . I love my 380s wish I had them all a long. boat flys nice and level now, but thats having the 2'' shortie two.

Re: Porpoise problem
 

Dave,

I removed the A/C water intake fitting from the bottom of the hull and blue printed the last four feet of hull.

We also did engine modifications at the same time. Overall I picked up a total of 4 MPH. There was a pretty good hook in my hull. It takes longer now for the bow to drop when coming on plane without tabs, but other then that you really do not notice any difference.

Is it worth it? Probably not.

Dock

Re: Porpoise problem
 

Playn,

You have one really sweet classic Baja.

Dock

Re: Porpoise problem
 

Thanks for the input Dock. I'm looking for little things to bring the overall performance up and my boat does porpoise. I'll just keep using the tabs. Thanks again for your input the other day on the phone too. Gave him a call.

Re: Porpoise problem
 

Always nice to talk with you Dave. Give me a call any time. I saw your post over on General Discussion regarding Tyler and the 496 engine. Let me know what you decide.

Re: Porpoise problem
 

I'm in the figuring out part with Tyler now. What is going to work best for my application and budget. Thanks again Dock