what pitch prop would you recommend?

[Srooney89]

i have a 2000 kenner 18 foot with a 2000 mercury 90hp 2 stroke on it. boat weighs approx. 2000 fully loaded with passengers, fuel, and gear. what prop size and pitch would you think? looking for top speed.

 

[Yegboats]

It's hard to say different hulls perform differently. Do you have any of the information listed in this link?
http://forums.iboats.com/forum/gene...p-questions-and-topics/295058-read-this-first

 

[Srooney89]

1) over rated rpm at wot at only 35mph
2) michigan wheel, stainless steel
3) 13 1/4 x 19
4) 6500 rpm with normal finishing load. motor rated at 5000-5500
5) 2000 mercury 90hp 2 stroke elpto
6) 2000 kenner 18v90, hull weight 950#, full load approx 2000#

 

[Srooney89]

also it is a 18v90 tunnel. the cavitation plate sits flush with top of tunnel. no trim tabs or hydrofoils or jack plate installed.

 

[Srooney89]

prop is 3 blade as well.

 

[Sea Rider]

When toon has deck weight evenly distributed and running at fast displacement speed or plane while running parallel to water level on flat calm no wind water cond are there OB water splashes over/out transom ?

To prop it right and assuming OB sits at the sweet transom height, need to perform a wot test with current prop as usually loaded, that's with a tach and ckeck max wot revs achieved. Will know the rpm difference between max factory stated and the ones achieved. On heavy combos going one less in pitch should dial a gain of + 200 wot revs.

Report back achieved wot rpm run, can go from there maximizing a new prop to take the max juice out of that 90 HP.

Happy Boating

 

[Srooney89]

no water over transom. ob is raised slightly and i begin to plane out i then slowly raise ob until the motor sounds smooth and good. raise more some times and it will begine to blow out then i drop back down to sweet spot.

 

[Srooney89]

i wont be able to get out onto the water until next week. i have had people say that i need to lose pitch which makes no sense. also had people say that i need to calibrate my tach which i cleaned all poles and made sure it was set to 6p. i just picked a prop off craigslist for a steal. brand new michigan wheel apollo 13x21 for $125. i think this prop will do much better and drop the rpms to a reasonable area. i just thought it was strange that the 19 pitch had 1000 rpms over motor rating.

 

[Sea Rider]

Can you post a pic of actual lower leg showing both horizontal plates, dialing perfect OB/transom height is a matter of checking visually what's going on at lower leg. playing rising or lowering OB and trying to guess perfect height without knowing which is the perfect leg parameter height is a waste of time and effort.

If tach reads well it's quite possible to have 1K + revs difference while ridding solo and heavily loaded. Is 90 HP the max transom rated for ?

Happy Boating

 

[Srooney89]

the boat model is 18v90 but they also made a 18v135 which i saw no difference on. i called manufacturer and they wouldnt tell me if i could go over 90hp. they said the boat was an "economy" model and that it was rated for 90hp. i think all they did was made it say 90hp vs 135hp. but it is rated for 90hp. everyone else says the 90hp on theirs is plenty of motor being able to wot in the low 40s and cruise low 30s. ill post a picture in a moment.

 

[Srooney89]

No Title

here are the pictures of the outboard setup as well as how i have the boat setup.

 

[Sea Rider]

Go for a wot spin on flat calm, no wind water cond.



Parameters :
-Deck weight must be evenly distributed
-Trim for boat and Anticav Plate to run parellel to water level at speed.
-Once on plane pull head out transom and check where is water flow at speed passing by through lower tail.
-Ideal lower tail height is for water flow to skim right under upper water deflector plate (red line)
-Flow must be cut at the sharp edge located right under upper plate. (green line)
-Test lowering or raising OB on transom till this cond is met.
-Once there can go for a prop maximization if in need to raise wot revs a bit.

Post final results, good luck!!

Happy Boating

 

[Texasmark]

Engine has 2.33 gear ratio which makes a 19 a little weak. If it were a 115 with 2:1 then the 19 would have been more suited....just shooting from the hip. 21 working for you depends on the prop dynamics and your setup but for $125 it's worth a try; I'd do it. If you miss put it on ebay and try again. I had that engine on my last boat.

Quick tach check....idle rpms in gear (no wake zone is a good place), boat in motion, spec is 675 +/- 50. If you are there you're close. If not set it there with your low speed adjustment on your throttle linkage under the cowl in the engine; white nylon knurled knob...it changes timing to set idle. Shift into N and let the boat stop it's forward motion. Jab it in gear. If it is a smooth transition, your tach is close.

Another tach check would be your hole shot with engine trimmed for fastest shot.....not necessarily tucked all the way in! If you are 1k over max on your WOT rpms, even with your 2k# of boat weight you should have a stellar shot, like 2-3 seconds from firewalled to when the bow comes back down.

 

[Srooney89]

ok so i took the boat out and tested the 21 pitch prop. I hate it. terrible hole shot and top speed was 33mph with trim set. rpms were at 6k. i swapped back to the 19 pitch and still saw 6k rpm and 33mph. but the hole shot was much better. i have a feeling my rpm gauge may not be correct. i got a hardline rpm gauge that will work with 3 cyl and will test it this friday. is there a chance that it could be possible to have a 17 pitch and gain more top speed?

 

[Texasmark]

ok so i took the boat out and tested the 21 pitch prop. I hate it. terrible hole shot and top speed was 33mph with trim set. rpms were at 6k. i swapped back to the 19 pitch and still saw 6k rpm and 33mph. but the hole shot was much better. i have a feeling my rpm gauge may not be correct. i got a hardline rpm gauge that will work with 3 cyl and will test it this friday. is there a chance that it could be possible to have a 17 pitch and gain more top speed?

I agree with you on bad information from your instruments.