Not happy with new Enertia

[mrclean]

My boat is a 18'6 Larson, 2700#wt with a 4.3 GXi (225hp) Volvo Sx 1.60 drive
The problem is I'm not much faster with the Enertia (a lot of money)
Look at mt numbers
Stock Volvo 14.5x19p Enertia 14.65x19 Enertia 14.65x17
Time to plane 5 sec 4.78 sec 3.8 sec
0-30 MPH N/A 10 sec 7 sec
WOT RPM 4600rpm 4400rpm 4800rpm
WOT MPH 48mph 52mph 50mph
I would think that my rpms should be higher than 4800 with the 17p
is this because of my low 1.60 drive? I put the 19p Enertia on a friends 19ft
Regal he has the 4.3 GXi BUT a 1.66 drive, he spins the 19p up to 4800rpms
at 52mph Why?
Gunner,
Do you think the Stiletto Bay Pro II would be better?
Thanks

 

[Tail_Gunner]

Re: Not happy with new Enertia

Well using a slip calc you show a positve 2% slip with the 17, so either your true speed is off or you tach is off. Did you use a gps to measure your speed? If so you need your to see if your tach is correct, sorry but that is where you should start


http://www.go-fast.com/Prop_Slip_Calculator.htm


Actually id have the engine looked at while your at it, if you take 1.60 @ 4800 with a 17p prop you get a theorictical speed of 47....and your real speed is 48. Check your tach and motor and gps lot's going wrong here.

My 186 (215 hp tbi) with a volvo drive 1.66 can turn a 21 @ 4800.. You do have a volvo drive dont you?

 

[mrclean]

Re: Not happy with new Enertia

The speed was done with a GPS. How do I check the tach? The boat is new
so I would think it's ok, and if it was off shouldn't the revlimiter kick in?
Or is it that my motor doesn't have enough hp or tq for this prop.

 

[Tail_Gunner]

Re: Not happy with new Enertia

Good new's is she's or should be underwarranty, go have it looked at closely. And yes it should hit the rev limiter using a 17p quite easily, ill bet your having somekind of timing advance issue going on but something's up.

I guess you could go into the I/O section and ask Don or Bond-o what is going on, those guy"s are some of the best. Just explain to him that your boat is doing 47mph gps and your using a 17p prop and your tach is showing 4800, while other boat's almost identical can turn a 21p prop to 4900, the 1.60 gear's vs 1.66 make litte difference and make sure he know's the tach is off......... One cannot have a positive slip which your does.... maybe something is just unplugged.

MR clean i must ask, you are trimming out your drive when you are running at speed??

 

[mrclean]

Re: Not happy with new Enertia

I can get to 50mph at 4800rpms with the 17p. With the stock Volvo 19p alum
I would go 48mph at 4800rpms. as far as the trim, I would watch the GPS and the tach to see where I could get the best numbers as I was trimming up or down.

 

[Bry21317]

Re: Not happy with new Enertia

I agree that it seems something is wrong with this Motor. I have a 94 Crownline 19'6" Bowrider that weighs 2900lbs with the Mercruiser 5.0l and 1.65 Gears in the Alpha 1 lower unit. I can turn a 21 pitch aluminum to 5000 rpms at 50 mph. I can also turn a 21 pitch Rev 4 SS prop up to 4800 rpms at 49 mph. I have a 2 bbl carb, and your motor has more power than mine does. So I would think you should beable to turn a 21 pitch Enertia no problem. I am thinking about purchasing this prop also, over the winter as I have read great things about it.

Bryan

 

[mrclean]

Re: Not happy with new Enertia

UPDATE,
I went out today to the lake it was alittle windy with a 1ft chop
I put the stock Volvo 19p alum back on the boat with this prop
WITH the wind mph was 52 at 4900rpms AGAINST the wind at was
50.5mph at 4750rpms. does this still sound wrong? I then put the
17p Enertia back on, it went 50mph at 4900rpms. Could it be that
the Enertia is just the wrong prop for my boat?

 

[stevens]

Re: Not happy with new Enertia

According to those last numbers, the stock prop gives you a slip of 5% (both with and against the wind) and the Enertia of -2%, which is impossible ( see http://www.go-fast.com/Prop_Slip_Calculator.htm ). Even if you add 1" for the cupping of the Enertia, that still yields a slip of 4%.


4-5% seems unlikely low, so your tach or speed readings may not be accurate. Probably wise to have the tach checked first, and also check to see if your GPS is set to MPH and not Knots.

If, however, the 4-5% slip is accurate, that would be hard to beat for any prop.

It could just be that the stock prop is exactly optimal for your boat/engine/load combination - in which case you now have a shiny, expensive spare prop....

Or, it could be that your revs are kept down by some mechanical or trim issue, in which case you should look into that before spending more time & money on props....

 

[mrclean]

Re: Not happy with new Enertia

Thanks,
I have checked everything but the tach, I want to make sure before I take it
to the dealer. It just seems that there is a big difference in the two props.

 

[stevens]

Re: Not happy with new Enertia

Well, both props yield extremely low slip numbers, meaning they're both pretty darn good for your boat.

I'm thinking your problem lies elsewhere - either the tach reads too low, or something is restricting your RPMs getting up where they should be. The problem could be mechanical, a fouled bottom, or a trim issue. Either way, have the dealer look at it under the warranty.

 

[John_S]

Re: Not happy with new Enertia

According to the larson website: http://www.larsonboats.com/senza/186/specs.asp your wot speed seems to be in the right range. Maybe, you don't have the gear ratio you think you have. This 18'er has more deadrise and is heavier than other 18'/4.3L combos, that will run mid to high 50's. So, you would expect more slip than what is being calculated.

 

[stevens]

Re: Not happy with new Enertia

I've been thinking about this thread a bit.

It's been suggested that you may have a different gear ratio than 1.60. However, that's the lowest ratio for that engine, and calculating slip with higher ratios only yields even lower slip numbers.

Although your tach seems to give low readings (judging from the low slip rates), your speed is right where Larson says it should be.

The product bulletin for your engine (link) gives a maximum RPM of 4800, and you're getting 4900 as it is (perhaps even bumping against the rev limiter?).

I've been thinking your tach is reading low, but may have been wrong about that.

As such, you're getting good speed and RPMs where they should be, and really low slip numbers. That suggests that you may want to leave well enough alone.

As for being disappointed in the Enertia versus the stock prop; they both give you good speed, RPMs in the right range and low slip - suggesting they're both excellent for your application. You may in fact be propped exactly right with both props and it is perhaps unreasonable to expect getting any more speed out of that boat/engine/load combination.

 

[mrclean]

Re: Not happy with new Enertia

Stevens,
The boat runs great with the Volvo 19p alum. prop (rpms & mph) I was
just expecting more with the Enertia, and I can't find anyone using a 1.60
ratio most are at 1.66 or higher.
Thanks