94 JC 266 tritoon 4.3 alpha one... need prop advice

[Lakeshore2016]

I just picked up the boat tonight. I can't find the size or pitch of the prop stamped on it. Don't know how reliable the rpm gauge is.... But it turned 5800 to 6000 full throttle. I'm hoping it was wrong, but this prop looks too small also. Anyone have any ideas on its size? It currently has a 4.3 mercruiser 4 barrel new vortec heads, alpha one. Shouldn't it be 4400 to 4800 range?

 

[Scott Danforth]

put some people (load) on the boat and it wont turn that fast.

first step is always verify the tach

 

[ahicks]

I think your concern is justified. I agree it won't turn that fast when loaded, but that's WAY high. You already know where to look look for prop part number/size from your other post (under the locking tab arrangement). That may provide some guidance, but you're so far out in right field, I have to agree the tach reading may be inaccurate as well.

 

[Lakeshore2016]

I noticed the tach reading wouldn't "bounce" around too much under 3/4 throttle... but at WOT...it seemed to jump to 6,000 really quick.... and it stayed there.

I haven't had a 4.3 in a long time and never in a tritoon, it just seems so loud, the wood base seats just don't muffle the sound like a fiberglass i assume.

Would my two options be to... 1.) buy a digital tach reader to point at the crankshaft(probably fastest and most accurate?) or 2.) buy a new tach and hookup to existing wiring to see if it makes a difference.

 

[ahicks]

I can think of a third option. A decent mobile tech SHOULD have a portable tach, AND provide you with the benefit of some additional boating experience. If you do some calling around to a few local techs, one may jump out as clearly more experienced when talking to him about your issue.

He could verify your tach is good or shot (if it's good, he just paid for his service call), AND possible share some experience on how to proceed from where you are at.

 

[Lakeshore2016]

I've been researching those "digital laser photo tachometers". Can pick them up from anywhere from 15 and up bucks. Unfortunately, all the auto parts stores and such don't stock them. So much for trying that out this weekend. Any chance someone knows how to use a multi-meter to test RPM's? Otherwise mobile mechanic may be a good choice or wait and order a cheap laser tachometer.

 

[Scott Danforth]

https://www.amazon.com/AGPtek-Profe...d=1503703748&sr=8-3&keywords=photo+tachometer

amazon prime

 

[Scott Danforth]

Harbor freight

https://www.harborfreight.com/lcd-automotive-multimeter-with-tachometer-kit-95670.html

https://www.harborfreight.com/digital-photo-sensor-tachometer-66632.html

 

[Lakeshore2016]

Ran it again today. I ran 23 mph at about 4400. Not even 3/4 throttle. Tach seems to be right up to there. But WOT jumps to 6K really quick, may not be quite 6K.... But I still think it's the turning too many rpms. Picking up a laser photo tachometer soon to check it at crank. Took prop off in my pictures in earlier posts... no stamps anywhere of diameter or pitch.

Can anyone give me a starting point with a prop suggestion ... since I don't have a base with my current ones specs.

I've seen the weight of boat stated at 2900 to 4400 lbs. I have no idea.

I've seen like 15 diameter with 15 pitch as a suggestion.

 

[ahicks]

Nobody wants to be part of an expensive mistake, so without more solid data, that's tough. The 15x15 doesn't sound too far out of line to me.

If you don't see diameter/pitch data perhaps you see a part number? If so, you could do a google search on that to get your dia/pitch data. RARELY do you not see this data, or a part number located somewhere on the prop.

 

[Lakeshore2016]

Just to recap:

1994 JC 266 Tritoon 4.3 mercusier alpha one
weight of boat looks to be 4400 pounds/but not quite sure/ JC website states *does not include weight of motor and gear. NADA states it at 2600... I know that cant be right. So I'm going with 4400.

I ran a 4 blade stainless steel prop with a 17 pitch/15 diameter... I turned 5100 RPMS with 6 adults/10 gallons of gas... I turned 5300 RPMS with 2 adults 10/gallons of gas. So I'm probably 300 to 500 rpms too high?

I'd like to be in a 3 blade for speed, suggestions on diameter and pitch?

 

[brsox88]

I run a 14" 4 blade with a 21 pitch and it gets me onto plan in under 5 seconds. RPM seems to be around 3300 at WOT and 48MPS so I can't complain but I need to confirm with the laser tachometer next time I am out. I'd probably do a 14-15" with a 19 pitch and you'd be right at where you want.

Boat: 18.5 Starcraft with 4.3l

 

[NYBo]

I run a 14" 4 blade with a 21 pitch and it gets me onto plan in under 5 seconds. RPM seems to be around 3300 at WOT and 48MPS so I can't complain but I need to confirm with the laser tachometer next time I am out. I'd probably do a 14-15" with a 19 pitch and you'd be right at where you want.

Boat: 18.5 Starcraft with 4.3l

If that's accurate, you are way over-propped. You are lugging the motor.

 

[ahicks]

I wouldn't be too concerned about the boat's weight. The focus should be on the prop data you have now - it's size, and what rpms are being run at this point. So we have that. What you don't mention is your target max rpm.

You say you're looking for more speed. You're not going to be pulling anything?

 

[Tritoon96]

I have a 1996 JC Tritoon 266. Had the same weight questions. I called the factory and this boat with a 4.3l is listed as 2650 lbs. I have a 4.3 vortec and use a 15x15 4 blade Turning point AL prop. Clean bottom and just me turns 34mph on gps at 4600 rpm. Right in the 4400-4800 range. Tried a 15x15 4 blade SS prop and rpm dropped off. I’m going to try a 15.3”x 13 pitch 4 blade SS from turning point next but really need the bottom cleaned. River in Toledo OH has a lot of algae growth.