how to get boat from 0-25mph faster?

[conk3416]

Re: how to get boat from 0-25mph faster?

these are the numbers on my prop: (48 79794 A5 17P) I believe it is a 17deg and is 3 fin but other then that im not sure. Can anyone tell me what prop i have?

Thanks Andrew

 

[cr2k]

Re: how to get boat from 0-25mph faster?

17 pitch. as in if water were a solid medium your prop would go 17 inches in one revolution.

 

[WizeOne]

Re: how to get boat from 0-25mph faster?

these are the numbers on my prop: (48 79794 A5 17P) I believe it is a 17deg and is 3 fin but other then that im not sure. Can anyone tell me what prop i have?

Thanks Andrew

Something is not adding up here. Merc 888's, in 16-19 ft boats, came with 21 pitch props. A 17 pitch prop is a way lower 'gear' and should allow that 302 to over rev, especially with only the driver aboard.

 

[JasonB]

Re: how to get boat from 0-25mph faster?

Yup, something's not right here.

I have a 888 set up (est. hp is about 210) in a fairly heavy 19' bowrider. Total boat+engine weight (empty) is about 2500lbs, then add 36 gals of fuel and a couple 225lb guys. I can spin a 21p Michigan Wheel 3 blade 4100 r's at 49mph. I usually run a 19p Hustler with heavy cup at 4150 rpm and 47mph. That 302 in a 16' boat with a 17p should wind through the roof if the engine is healthy. Part of me wonders if the prop is a large diameter (mine are all 14 1/4"), but that #1 drive doesn't have clearance for huge diameter wheels.

My 20hp over stock doesn't make that kind of difference.

That 500cfm 2bbl isn't a good idea right now. You need to figure out what is wrong first. I still run the stock 300+ cfm 2bbl on mine.

 

[scipper77]

Re: how to get boat from 0-25mph faster?

Nobody has suggested a compression check (I don't think at least). I would say lets see what we are working with from the motor side of things and then take it from there. Check compression, timing, dwell (if applicable). Look at the plugs while you are doing compression. It sounds like the carb is fine if you are hitting 4200 rpm's but then again what do I know?? If you don't have the proper equipment just keep an eye on craigslist. I got a timing light and dwell meter for $10, noone outside of the boating world needs a dwell meter anymore but many old timers still have them. If you are willing to take the time and buy a few inexpensive tools you know the guys here will not let you down. I have a 17' open bow with a 185 HP v6 and that thing flies!! Your set up sounds like a real monster for pulling to me.

Good luck to you.

///edit/// I stand corrected, Bubba1235 did suggest a compression test already ///edit///

 

[WizeOne]

Re: how to get boat from 0-25mph faster?

Nobody has suggested a compression check (I don't think at least)..

See below:

.......Also it sounds like you could be significantly underpropped for the load you are carrying. This all assumes that you are well tuned and have good compression. What is your WOT rpm with just you in the boat? Should be, give or take, around 4400 rpm which is the maximum operating rpm. A small boat with a big load can change that rpm easily. For best performance and to make the engine perform most efficiently, you need to be propped to reach maximum rpm considering the load you are carrying.......

 

[mylesm260]

Re: how to get boat from 0-25mph faster?

Agreed.

That 302 should rev freely to 5K with that setup easily.


On smart tabs:

EVERY IB/OB boat should have smart-tabs. they are fantastic!

IB/OB boats have a LOT of weight right at the stern.

I put smart-tabs on my 21' 4.3 powered boat and it handles completely different.


Not only does it plane MUCH quicker, but it can say on plane at MUCH lower speeds.

Also, if can take rough water and waves MUCH MUCH better than before...


Before smart tabs, I would hit WOT to plane, and my bow would go up to the sky..... Now the boat stays almost perfectly level under acceleration.

 

[erikgreen]

Re: how to get boat from 0-25mph faster?

I put some salvaged Bennett tabs on my 21 foot I/O two weeks ago, and believe me it's made all the difference.

It's a 4500 lb boat fully loaded with a GM 350 in it, and with the tabs it's not noticeably faster but it's much, much more comfortable. I can level it side to side so it doesn't list when I'm riding alone, I can point the bow down so my cutwater slices the waves just right, and at the right angle it glides across the water like a magic carpet.

I took it on superior for a drive and stood looking over the windshield to steer... we had less than a quarter mile vis due to fog, we had 1-2 foot swells, and it started to rain, but I was very comfortable and safe doing 17 knots to head back to the marina... before this I would have crawled back at 6 knots to avoid all the slamming and bouncing.

Erik

 

[conk3416]

Re: how to get boat from 0-25mph faster?

i did a comp. check, all cylinders were 130-135. I believe that iss a good number so we can rule out the compression problem.

Thanks for the help so far.