is it bad to have the boat plane too fast?

[dannieboiz]

I have a 5.7L engine with Cobra SX outdrive. I had a 14.75x17p 3 blade SS prop and WOT at 5k RPM

I wanted to bring my RPM down a little bit so I went with a 14.75x19p 4 blade prop and now when I floor it, the RPM raise slower but the boat shoots out of the hole and jump into plane almost immediately.

I picked a bad location to test the new prop in 4-5ft swells which cause my nose to dive right into the swells. riding it easy is ok, 3k RPM cruising at 25 mph.

With the old prop, I was doing around 43-44mph WOT in the bay and rivers, I'm not doing any bay fishing for another few weeks so I won't be able to test the WOT of this prop, but I wanna bet I'll be going as fast if not faster at only 4600 to 4700 rpm which is within range of 4600-4800 rpm based on what I've been reading.

So is it a bad thing that the boat jump right into plan? Also, it seems harder to lift the bow purposely when going over 30mph. Bottom line, the hole shot is just crazy.

It's a 21ft WA striper

 

[smokeonthewater]

Re: is it bad to have the boat plane too fast?

Are you SERIOUSLY worried that your boat works too well ... lol just kidding.... no it is soooooooooo not a bad thing..... if you want to take off more gently then use less throttle

 

[dannieboiz]

Re: is it bad to have the boat plane too fast?

Are you SERIOUSLY worried that your boar works too well ... lol just kidding.... no it is soooooooooo not a bad thing..... if you want to take off more gently then use less throttle

LOL that's what I thought, I just need to learn the boat all over again since the performance is so much different now. Until I can test the wot, I guess I can't say for sure it's the one. I scared the crap out of my passenger, I almost **** in my pants too.

 

[1979checkmate]

Re: is it bad to have the boat plane too fast?

the better response is most likely the case of a better propeller - not the pitch. 2 identical propellers, one 17 and one 19 pitch, the 17 would have the greater holeshot.

 

[dannieboiz]

Re: is it bad to have the boat plane too fast?

the better response is most likely the case of a better propeller - not the pitch. 2 identical propellers, one 17 and one 19 pitch, the 17 would have the greater holeshot.

The old prop was an ATTWOOD prop, the new one is a mercury prop but the 4 blade would add the hole shot but the main reason why i went 4 blade is the low speed controllability. I had to troll on the main motor last week when my kicker wouldn't start and let me tell ya, it's like having 4 wheel drive on the water, poor mans duo props LOL

 

[smokeonthewater]

Re: is it bad to have the boat plane too fast?

the better response is most likely the case of a better propeller - not the pitch. 2 identical propellers, one 17 and one 19 pitch, the 17 would have the greater holeshot.

not always...... depends on gearing, horsepower, and weight

 

[dannieboiz]

Re: is it bad to have the boat plane too fast?

This prop was the prop the previous owner used when he had a Ford 302, 5.0L in it. I never even did a sea trial on the 302 and went straight to the 350 that i have now. The 302 probably had 180 or so HP while the 350 is pushing closer to 280 but someone told me my engine is probably 300hp. That's probably why my WOT was too high to start with.

 

[zagger]

Re: is it bad to have the boat plane too fast?

Is your motor stock and carburetor or injected, just wondering. I'm taring to figure out what to get for my new prop.

 

[dannieboiz]

Re: is it bad to have the boat plane too fast?

carb motor with edelbrok carb.

 

[wbc1957]

Re: is it bad to have the boat plane too fast?

I always thought that when you had a three blade 19, you drop to a 17 if you went to a four blade. This would give you your hole shot, but still keep the RPM's within the best range for fuel use and performance. At least this is what I learned through experience and the prop section on this forum.

 

[mommicked]

Re: is it bad to have the boat plane too fast?

Its bad if all passengers are"nt seated or holding on to something when you nail itI put a 4 blade on my 18' jonboat and it grabs the water alot more than the stock 3bld. at any speed.Ive heard here that 4 blades help raise the stern and it certainly did on my boat.you may need to trim more to get your bow up,but im no expert.

 

[gimmieaclue]

Re: is it bad to have the boat plane too fast?

"I always thought that when you had a three blade 19, you drop to a 17 if you went to a four blade."

I may be wrong but I thought 4 blade props were even 16,18,20inches and 3 blade props are odd 17,19,21 inches. Been wrong before thought

 

[wbc1957]

Re: is it bad to have the boat plane too fast?

"I always thought that when you had a three blade 19, you drop to a 17 if you went to a four blade."

I may be wrong but I thought 4 blade props were even 16,18,20inches and 3 blade props are odd 17,19,21 inches. Been wrong before thought

Sorry, but four blade props do come in both odd and evenly pitched sizes. The normal process for changing from a 3 blade to a four blade, is to drop the pitch by two, while maintaining diameter. Hence, a 19 pitch 3 blade could mean a 17 pitch four blade (odd number).

 

[smokeonthewater]

Re: is it bad to have the boat plane too fast?

folks.... he had increased horsepower by 50%.... he needed a lot more pitch so he needed the prop he chose OR a 3 blade prop with even more pitch