Too much prop?

[bpmcl00]

Hey guys. i have a 19 foot bowrider with a 4.3lx merc motor. The current prop is a 23 pitch, which i believe is too big.

while cruising the boat planes at 10MPH and the whole front of the boat rises dramitically, literlly anything not strapped down on the front of the boat comes flying towards the back. its quite annoying cause i cant even see over the bow when this happens, i have to stand up and drive in order to see where im going..

i try adjusting the trim but no major differnce. the boat still wants to stand STRAIGHT up.

it will finallly level off after about 30 seconds, then it picks up speed and the bow drops down.

once i get to about 25-30 MPH there is no issue. its only slow speeds like maybe quarter throttle

also WOT for my boat is around 4800RPM i am not able to reach this with just me on the boat. closer to 4500. (by my tach on the dash)

What do you guys suggest?

Thanks

 

[steelespike]

Re: Too much prop?

Speaking generically some I/Os do have planing issues.Trim tabs or smart tabs would help.It appears that a change to a 21" pitch would improve your hole shot and probably get your rpm in the right range.If it continues to struggle to plane you might want to check that the foam under the floor hasn't absorbed water.Also be sure the mnotor is well tuned and getting full throttle.Good compression? Observe the way it sits at rest.Is it level side to side?does it seem to sit really low in the stern.Perhaps you could weigh it.
A 4 blade prop will usually improve low end performance at a slight sacrifice of top end.

 

[wca_tim]

Re: Too much prop?

I'll mostly echo steelspikes comments...

All of the smaller i/o s I've had have exhibited characteristics like you describe to some degree. It is pretty much due to that big chunk of iron sitting in the azz end (probably a fourth to a third of the entire boats weight a couple feet from the stern...) I agree that you'll probably be happy with a change to a 21" prop. There are a lot of options, but for the money and performance characteristics, a Solas Titan 4 would be hard to beat - especially if you're interested more in all around performaqnce, water sports, etc... Depending on the 3-blade you have now, you'd see more stern left (and less bow lift...) and would get a noticable increase out of the hole. May have to watch rpm's at wot, but would be hard to tell without trying. It may run a little faster than what you have now, but just as likely will lose a couple mph on the top end. They sell the Solas line on here for competitive prices (I'm not affiliated, just a satisfied customer). I own two Titan 4 blades. You can pick one up new for ca. $300.

The biggest help for getting up on plan and controlling bow rise will come from a set of trim tabs. I can imagine that you would be really pleased witha set of the sx series smart tabs. I liked the set I had and have several friends who like theirs. I broke a set but that was going quite a bit fasted than you will with your current set-up. The handling in chop, bow rise control and ability to maintain an even plan at lower speeds when pulling wakeboarders, was striking... like being in a different boat alltogether.

Regarding the waterlogging thing... can pull stuff apart and check, or another option if it is convenient is to weight the trailer and then weigh the boat and trailer together (with tank either full or empty, all the gear removed, etc...). Water is really heavy and if it is a problem will be obvious when you compare actual with specification for your boat and engine combo. If you have large foam filled boxes on either side of the engine, they can hold a ton of water... and would make it really heavy... would increase the tendencies you're asking about.

Hope this is helpful.