etec 90 on avon 5.4 prop

mcinfantry · 02 July 2008, 03:35

ok, swapped to a 90hp etec. all speeds gps measured.

ran today a couple hours. the motor is 20" all the way down and trimmed all the way down the cavitation plate is even with the bottom of the drain hole, not the keel. also, the motor is mounted in the original holes, DEAD center in the transom.

i have a 13 1/4 x 17 stiletto stainless steel propeller. i can get 4700 rpm and 39mph with about 40 liters of fuel, and 3 occupants. i have converted center console and leaning post.

if everyone moves to the back of the boat (except me) and ducks down out of the wind we could hit about 4900 rpm and 41mph.

according to the prop calculators, at 15% slip my prop is actually about 20.62". so to get 5200 rpm with a 15% slip i would need a 19" propeller.

i took the low-end on the slip... high end is 30% and the 17" is actually around 25". and i would need a 20" propeller.

i plan on adding a ice chest/seat in the back so i can fish in the thing. but that adds weight, and i also plan on adding a trampoline top to keep the sun from killing me.

my questions.
1) i realize my boat motor needs to be moved starboard about 1.5". would i expect any rpm increase/decrease?

2) what should i do on the propeller? go to a stilleto 15"? get mine custom reworked? change brands? or keep running it as-is. is it bad the motor will not go above 4700?

im not really concerned with speed, just hitting 5200rpm, or should i care?

Chris · 03 July 2008, 00:20

with a 90HP Etec on a 5.4 searider I am suprised you are only getting 40mph.

MattH's old Searider with a 90hp Yamaha got close to 50 MPH.

I would say you need to look at your set up as something is amiss.

Also are you sure you GPS is displaying speed in MPH and not in Knots?

mcinfantry · 03 July 2008, 04:24

Quote:

Originally Posted by Chris

with a 90HP Etec on a 5.4 searider I am suprised you are only getting 40mph.

MattH's old Searider with a 90hp Yamaha got close to 50 MPH.

I would say you need to look at your set up as something is amiss.

Also are you sure you GPS is displaying speed in MPH and not in Knots?

well, i remounted the engine 1.5" starboard today and moved it up one hole. i was tempted to go two, but cant find anyone who has run two holes up. i hope to run it tomorrow

mcinfantry · 04 July 2008, 03:22

huey, when you say third hole, do you mean third as counted from the top, or from the bottom? when i am one hole up, that means i am on the 3rd hole from the bottom of the 4 holes, i can raise it two more before i am out of adjustment.

i ran it today for 35 more miles (56 yesterday) and with 26 gallons gas, 2 up, we got 42~43mph.

day 1, 3 people, 12 gallons fuel, the trim gauge showed about 3/4 of the way trimmed up. 4700rpm and 39mph

day 2, 1.5" starboard, 1 hole up, 26 gallons fuel and the trim gauge was slightly above the "tick" and 42~43 mph 4900~5000rpm. if i trimmed up to yesterdays mark it would lift the nose slightly higher and "chine walk"... trimmed back down it kept speed.

where should the anti-ventilation plate be in the water??????

heres a picture of mine. you cannot see it at all when on plane at 4900~5000rpm. should i go up another hole?

Nos4r2 · 04 July 2008, 09:36

You're actually about right with 42-44mph given the amount of gas you're carrying. With 132 litres aboard (32 US gallons) and 2 people I make 36 knots or 42mph. Weight (and its distribution) is quite critical too-with a load of camping gear in the bow a few weeks ago I couldn't pass 32 knots.

Take it for a run with just yourself aboard and 12 gallons and you'll be surprised at the difference it akes.

Chris · 05 July 2008, 20:26

Mcinfantry I would lift it another inch or maybe even 2.

The chine walking you are experiencing is one indicator that the engine is still too low.

mcinfantry · 05 July 2008, 21:00

Quote:

Originally Posted by Chris

Mcinfantry I would lift it another inch or maybe even 2.

The chine walking you are experiencing is one indicator that the engine is still too low.

im trying to find some riders!

thanks for the response! im less than 30 minutes from lake maurepas (91 square miles).

reinier · 05 July 2008, 23:25

Quote:

Originally Posted by Chris

Mcinfantry I would lift it another inch or maybe even 2.

The chine walking you are experiencing is one indicator that the engine is still too low.

Yeah I agree, chine walking in a boat like that with just over 40mph won't happen when it's set up right.

ian parkes · 05 July 2008, 23:50

you are getting the same revs etc as i did with a 17" prop . I now have a 15 and its revving where it should . top speed hasn't changed but holeshot and midrange is much better . main difference was the fuel consumption improved a lot with the lower pitch prop , i think making the motor labour with too higher pitch makes it use lots more fuel

mcinfantry · 06 July 2008, 04:31

i wonder if my tach isnt off..... anyway, im going to try a 15" pitch. maybe a 4 blade, it ran 40 with 3 today, and on 3rd notch. ventilates in turns more than i like.....

Nos4r2 · 06 July 2008, 09:34

Quote:

Originally Posted by mcinfantry

i wonder if my tach isnt off..... anyway, im going to try a 15" pitch. maybe a 4 blade, it ran 40 with 3 today, and on 3rd notch. ventilates in turns more than i like.....

It's too high.Ignore what Chris and reinier say about height, all you'll do is make it cavitate too much.Mine will chinewalk at high speed/high trim angles too. It's what happens to a Searider when you trim too far out at high speed and have a lot of weight in the stern (like 26 gallons of gas and people...)
If you don't have exactly the same prop but in 15" as you were using then the results will be invalid for comparisons.It's worth trying a standard ally 17" or 19" pitch on it though to get a benchmark.

I'm running a Yam 85, one hole up, same gear ratio as the Etec too and I run a 19" pitch standard ally prop for the same RPM/speed results.

Remember, 90hp is 90hp.
The 'Near 50mph' that Matt H's old 5.4 with a Yamaha 90 did was actually just short of 40 knots-45 mph-and the Yamaha 90 is a lighter engine at 122kg Vs the Etec at around 145kg. Matt H was solo at the time too,carrying less fuel and he's not a big bloke.

matt h · 06 July 2008, 09:41

your right chap, leave the height and take people out, cos you aint going to get any more than 39 knots light!!

mcinfantry · 06 July 2008, 15:53

Quote:

Originally Posted by Nos4r2

It's too high.Ignore what Chris and reinier say about height, all you'll do is make it cavitate too much.Mine will chinewalk at high speed/high trim angles too. It's what happens to a Searider when you trim too far out at high speed and have a lot of weight in the stern (like 26 gallons of gas and people...)
If you don't have exactly the same prop but in 15" as you were using then the results will be invalid for comparisons.It's worth trying a standard ally 17" or 19" pitch on it though to get a benchmark.

I'm running a Yam 85, one hole up, same gear ratio as the Etec too and I run a 19" pitch standard ally prop for the same RPM/speed results.

Remember, 90hp is 90hp.
The 'Near 50mph' that Matt H's old 5.4 with a Yamaha 90 did was actually just short of 40 knots-45 mph-and the Yamaha 90 is a lighter engine at 122kg Vs the Etec at around 145kg. Matt H was solo at the time too,carrying less fuel and he's not a big bloke.

the reason i ask about the tach, is the prop is it will NOT spin above 5000 rpm, no matter what i trim it to. even at this height. even when it ventilates. its broken in now, has to be. ive probably got 10 ~ 12 hours on it.

Nos4r2 · 07 July 2008, 01:52

Quote:

Originally Posted by mcinfantry

the reason i ask about the tach, is the prop is it will NOT spin above 5000 rpm, no matter what i trim it to. even at this height. even when it ventilates. its broken in now, has to be. ive probably got 10 ~ 12 hours on it.

Did a bit of google-research and it appears that the etecs run a lot higher oil/fuel ratio til the engine has done 10 hours over 2500 rpm. Has your 10-12 hours all been above 2500 rpm?

I really wouldn't expect to make the boat any faster carrying the load you do anyway but the 5000 rpm thing is slightly puzzling.

mcinfantry · 07 July 2008, 01:57

Quote:

Originally Posted by Nos4r2

Did a bit of google-research and it appears that the etecs run a lot higher oil/fuel ratio til the engine has done 10 hours over 2500 rpm. Has your 10-12 hours all been above 2500 rpm?

yes, i ran another 3 hours today. i bet im close to 15~18 now... at least 12 are 3000~5000

Nos4r2 · 07 July 2008, 02:08

Quote:

Originally Posted by mcinfantry

yes, i ran another 3 hours today. i bet im close to 15~18 now... at least 12 are 3000~5000

I've just been looking at pics of your prop. Is it the Stiletto Advantage series?
If it is and you have one then stick a standard ally 19" pitch prop on and try it.I think there's a fair possiblity of the RPM coming up. Just a 'hunch'...

mcinfantry · 07 July 2008, 02:21

Quote:

Originally Posted by Nos4r2

I've just been looking at pics of your prop. Is it the Stiletto Advantage series?
If it is and you have one then stick a standard ally 19" pitch prop on and try it.I think there's a fair possiblity of the RPM coming up. Just a 'hunch'...

it is a stilletto advantage. if i want to stick with ss, then whats your suggestion?

Nos4r2 · 07 July 2008, 03:11

Quote:

Originally Posted by mcinfantry

it is a stilletto advantage. if i want to stick with ss, then whats your suggestion?

1st bear in mind the only time I've seen a Stiletto Adantage is in a picture (not made here etc...), but it looks to be quite heavily cupped. In my experience 5.4 Seariders don't seem to do too well with a heavily cupped prop. I think it'd be worth trying one with less cupping if you can find one.

It's hard to comment on makes when you've got a far superior selection in the US.

mcinfantry · 07 July 2008, 03:17

Quote:

Originally Posted by Nos4r2

1st bear in mind the only time I've seen a Stiletto Adantage is in a picture (not made here etc...), but it looks to be quite heavily cupped. In my experience 5.4 Seariders don't seem to do too well with a heavily cupped prop. I think it'd be worth trying one with less cupping if you can find one.

It's hard to comment on makes when you've got a far superior selection in the US.

ok, im going to hit up a prop shop tomorrow. ill keep the thread going, to save others time and money. as i realize not everyone is as close to such varying types of fresh and salt water.

Nos4r2 · 07 July 2008, 03:42

Quote:

Originally Posted by mcinfantry

ok, im going to hit up a prop shop tomorrow. ill keep the thread going, to save others time and money. as i realize not everyone is as close to such varying types of fresh and salt water.

Fair enough

Here's my thinking behind what I said:-
A while back I did the sums on the slip % on a few props I was using. I found that at cruising speeds I was getting around 10% slip, which is pretty good. At WOT speeds though I was getting in the region of 24% and the slip % started increasing markedly at about 30 knots.

AFAIK cupping should come into play at higher speeds where it effectively increases the prop pitch when you're getting more HP from your motor-but... The Searider hull isn't a particularly fast hull and I think it's putting that much extra loading on the motor that the revs won't come up.

I suspect if the hull had a planing pad then the results would be noticeably different.

It'd be nice if someone could tell me if this makes proper sense!