Prop blowing out!
 

New to the site and have a prop blow out ? Got a 88 baja force with 350 with about 325 hp. From idle I go wide open the boat comes up on plane and then the engine revs up to 5000 rpm and the boat just don't go any faster. I can see water shooting behind the boat like the prop has come out of the water but I know it is not. If I baby it the boat will come up on plane to about 2400 RPMs and then if I give it more throttle it just revs up and a boat does not move any faster. All of this is with the out drive tilted all the way down and Trim tabs down. Once up on plane and running full speed trimmed out if I try to slow down at all the boat just loses push the prop start slipping or something and I have to completely stop and start all over. I want to video tape to show what I mean cause it's kind of hard to explain. It has the stock aluminum 19 pitch prop on with through hull exhaust. I just rebuilt the engine over the winter and have a little bit more power now and I've never experienced this before so I really have no idea what's going on I'm used to bass boats not big pleasure boats!!!

Do you have a rubber hub prop? If so, you may need to have the hub replaced because it's slipping. That would explain most of your symptoms.

+1

Yup it's rubber but it is marked and is not spinning. I can baby it and get it up and going and can see behind the boat the water the prop is pushing. It won't take much trim before I start getting a rooster tail. I have had it to 45 mph at 5200 rpm but if I pull back to 3500 rpm it looses bite and I have to stop and start over. I'm trying a diff prop next week but I'm thinking its ok but maybe not.

Try a different prop and see what happens.
Do you have thru hull or thru drive exhaust?

I'm meeting my buddy tomarrow to get a prop and try. It has threw hull exhaust. The ring is gone off the end of the prop as it broke. I'm not sure if that matters as the exhaust does not go threw the prop.

Guess I should put it has the factory aluminum prop from 88 still on it I believe.

Ring on the end of the prop is broken?

Once on plane put the Trim Tabs up, or try getting on plane with them already up and not using them.
Or the drive coupler is blown out and slipping

Just put a new drive coupler in last week cause it went bad. There was a ring on the end of the aluminum prop that was tapered and it broke off.

Two thoughts - something in front of the prop is disturbing the water flowing to the outdrive (transducer, speedometer, barnacles, etc) or the aluminum prop is flexing and losing enough pitch to cause cavitation. I would run a stainless prop on that boat!

^^^^^ This!. Alum props even preform like CRAP on a small fishing boat with a 100 hp O/B. Now you want it to push a 5000 lb boat with triple the HP!

sounds like you are talking about the diffuser ring, the last part of the barrel that flares out at the end? if that fell off it is time to throw that prop in the garbage and buy a new one, also with that power the boat will run much better with a stainless prop the aluminum flexes to much as somebody else mentioned.

Yes that's it the diffuser ring. It's gone. Picking up a prop tonite to try it. I have always wanted a stainless prop for it.

Uuuummm yup it was the prop. Got a stainless steel prop on it and it runs great. Thanks for the help guys..

I have the same boat. Mine also came with the 350 Mag / Alpha with a stainless Mirage 19" prop. I was getting about 52 mph at 4800 RPM with a light load on a good day. Enjoy the boat - hard to beat the cockpit and storage space on a boat that size.

Mine had the 260 horse 350 but I changed that turd out for a motor I had built for a car I never bought. I was getting 55 mph GPS with a 20" at 4400. I think I need a 19 but it comes out of the hole real good with the 20". I love the space in the boat and the cabin. I'm ready for a bravo and my 434 I got setting here to go in this winter!!!!

Force hulls are hard to get "going fast". Mine is doomed at 55 mph with 502 efi and 23" mirage plus wheel. \

92NSX, I agree that these are far from fast hulls, but a buddy of mine has an 89 Force 235 and he was seeing 80 with a 502 and B&M supercharger. Currently he is running around 70 with a 500 HP clone. I am hoping to join the 70 MPH club with the new 489 that I am building, but I'll believe it when I see it.

So2fast5u, just for reference, I swapped my 260 HP 350 Mag for a warmed over 454 and B1 (1.36 ratio) with a 21 Mirage, and went from around 53 mph to around 60 (on a good day). Most of the time I was seeing around 58 - 59. So my point is don't expect too much, even with the 434. Also, not sure how much benefit you will see going from the Alpha to the Bravo. Bravo's take more HP to turn, and have more drag in the water. Yes, they are more durable, but if you are putting less than 400 ft/lb through them and avoid the hole shots and launches (unlikely with this hull), and add a good drive shower, I see no reason why the Alpha couldn't live behind a small block. For the cost of the Bravo upgrade, you could probably stockpile a couple of spare Alpha's just in case.

My 434 is 650 hp but its at 7000 rpm. I will have to change the cam to lower the rpm range. I plan on making a drive shower here soon cause I'm scared of the alpha blowing apart. I have saw a clamed 80 mph with a 600 hp big block in the 235. It really is just a good boat for running around in I think. It's not a speed boat that's for sure. I would rather have a bravo then mess with replacing alphas all the time but it is $$$$$