SST 15", 17" prop comparison for 90 etech

[snodger 08]

Hi all,
I have just had my 90hp 2006 etech in for a service, and the tech recomends I go up to a 17" prop from a 15. Mind you I am getting 5500 RPM at wot, but he thinks that a 17 will launch the boat up on to a plane quicker. I am a bit unsure about spending $8-900 on a new prop if it only makes a marginal difference, so I was wondering if anyone has a 13 spline 17" sst prop that I could borrow and do a trial with, so I can make a comparison before spending the big bucks. I would post any results on the forum to help others out with a similar problem.

Cheers

Steve

[Blackened]

G'day

Fire your tech.

Going UP in pitch will NOT get you out of the hole faster.

Is that 5500RPM in the range for your engine for WOT?

What hull have you got and what diameter are these props?

Dave

[hhb470]

hi steve,
i have a 90 etec on a haines hunter 470 breeze.
over the last 12 months i thoroughly checked out prop selection for my rig because i thought the prop was wrong, i run a sst 13 7/8 x 17.

the facts are.
WOT is between 4500 - 5500:
IDEAL WOT is 5200.
I was achieving 5000 - 5100.
I lifted my motor (1 hole) to the third top hole.
WOT increased to 5250.
At 5500 you maybe running a bit high considering 5200 is ideal, above 5200 HP peaks out.

What mounting hole is your engine bolted to?

BRP has a FREE test porpeller service.
If you contact your local BRP dealer he can get a test prop.
All you pay is the freight charge for delivering the prop, cheaper than buying one that does not correct the problem.

cheers nick

[stinky-stabi]

the 17 will bring it down about 400 rpm
i have 90 etec 07 model with 15 viper it runs at 5200@wot for 34/35 knts


tono

[Outsider1]

Hi Snodger,

not sure about the 2006 but the ideal WOT range for the 2007 and 2008 model 90hp is 5000 to 5200. 5200 should be your aim with a light load.

As Blackened said a higher pitch prop will not improve your holeshot, in fact will probably make it slower. Assuming a similar design prop style a higher pitch will increase your top speed slightly, (assuming slip does not increase substantially) reduce your holeshot slightly, and decrease your WOT rpms slightly.

Your motor height needs to be checked first. I know a dealer that says he rigs on the 3rd hole up. Go to the E-Tec Owners forum and you will get the info you are after;

http://forums.etecownersgroup.com/mb/barnaclebill

Cheers

Dave

Edit: just saw Stinki Stabi and hhb470's posts and they are also on the mark

[snodger 08]

Thanks for the replies guys.
Dave, It's on a 4.8 Gale Force with a 13 7/8 X 15 on it at the moment. WOT is between 4500 and 5500.
Nick, form what your saying it may be worth just dropping it down a hole to see how it goes as the tech did say that when he trimmed it up it seemed to spin its wheels between 5200 and 5500 without gaining any speed. If that fails I will try the BRP test prop idea.
Tono & Dave, it was my belief also that by going up in prop size, I would get less hole shot.
Thanks for the help guys, as this tech realy had me confused. heading to the etec forum now.

Steve

[Blackened]

G'day

May be worth contacting galeforce themselves, reason I say this, is i'm sure quite a few of their boats have been fitted with 90 etec.

May be worth asking for contact details of owners with the same rig as you and chew the fat

Dave

[hhb470]

hi steve,

the best advice i can give is to get your motor height right to start off with first.
e-tecs like it a bit high, this being the case lift your motor to the 3rd top hole.
most dealers will start at this point.

then if ideal WOT (5200) is not achieved start playing with different props.
generally speaking Viper is the way to go for every day usage.

all boats are different.

what height is your motor set at the moment???

[FNQCairns]

Anyone know what the e-tec definition of 'ideal' is?? Ideal for who or what, where and why, why.... as it relates to known engine understandings as opposed to marketing or "this prop lineup is all we got" reasoning.

How come an engine that stratifies it's fuel charge different and it's timeing but MUST still follow the same physical laws as every other engine out there have an 'ideal' RPM for 'ideal's sake only it seems?.

cheers fnq

[hhb470]

too techical for me!!!!!!!!!!!!!!!!!

if the MANUFACTURER of the motor advises that WOT is between 4500-5500 but ideally 5200 is the "sweet spot" what is so hard to understand about that?

now knowing what the "sweet spot" is you then must tune the motor height and prop selection to suit.

[FNQCairns]

too techical for me!!!!!!!!!!!!!!!!!

if the MANUFACTURER of the motor advises that WOT is between 4500-5500 but ideally 5200 is the "sweet spot" what is so hard to understand about that?

now knowing what the "sweet spot" is you then must tune the motor height and prop selection to suit.

No worries I suspect no one can explain it manufacturer included to any plausible level.

Manufacturers have a long and solid history of advising engine RPM ceilings that those in general use find out too late is too low for good and lasting performance. The 'ideal I suspect relates directly at the prop line up available. Guaranteed I could get a 90 without trickery or anything special performing 6% better than 'ideal' ever could no more stress and around 7-8% better fuel economy.

Fair dinkum I think this 'ideal' is a con, wish I had an easy and extra 300rpm minimum up my engines sleeve to move forward with, it's tapped out at 5650-ish. It's that last 3-400rpm that turns aa average bat into a good boat -not because it is at the end of the rpm range but because it effects all rpms below.

cheers fnq

[FNQCairns]

Hi all,
I have just had my 90hp 2006 etech in for a service, and the tech recomends I go up to a 17" prop from a 15. Mind you I am getting 5500 RPM at wot, but he thinks that a 17 will launch the boat up on to a plane quicker. I am a bit unsure about spending $8-900 on a new prop if it only makes a marginal difference, so I was wondering if anyone has a 13 spline 17" sst prop that I could borrow and do a trial with, so I can make a comparison before spending the big bucks. I would post any results on the forum to help others out with a similar problem.

Cheers

Steve

You may get away with it, but only if the 17p is of a small diameter like of the 13.25 variety. If you can try before buying and test with the boat heavy, it may be worth sucking it to see?

cheers fnq

[Wear the fox hat]

Stay with the 15" prop. I put a 90 E-tec on my 5.2m Quintrex centre console & it was originally fitted with a 17" standard S/S prop. Changed to a 15" Viper & the hole shot is fantastic. Max revs now (at a guess) would be about 5400, but at 5200rpm the speed only decreased from 33kt to 31kt which is fast enough. People that want to do 45kt or faster are only an accident waiting to happen.

WTFH