The Viper Has to Go!

Ian M · 18 July 2012, 17:43

I've been running a 19" Viper prop and have finally had enough! Poor hole shot and not such a good top end. The etec revs out to 5600 no probs, and gets there impressively quickly! So poor bite from the prop and I suspect that I am getting excessive slip. I've tried a 21" Rebel but it was too much and I only managed to get 5000 rpm. The local dealer is unwilling to get a prop in for me to try, despite recommending a 19" Rev4 4 blader. I have to buy without trying, which I am reluctant to do.
So, does anyone know of a dealer who might be willing to loan a 19" Rev4 for me to try? Obviously if it is OK, I'll buy it, likewise if a ding it

One of the factors that I want to try out is engine height, at the moment I am running one hole off of the bottom as the Viper is known to run higher than some props, hopefully dropping it one hole will be sufficient. I know it is a long shot, but has anyone any direct experience of a Rev4 on an etec on a 6.5 Vipermax?

Pikey Dave · 18 July 2012, 17:55

Not quite, but I have rev4s on my twin 115s on a 6.4 ribcraft. Originally the engines came with 21"vipers, they were the equivalent of slicks on a car, no grip & continually blowing out in the rough or in turns. Mike Vincent at South Coast Marine suggested the Rev4s & I haven't looked back. He let me try 19 & 21" on a try before you buy, I went for the 19inchers. They are a bow lifting prop, in that they "dig in" & hook the stern down, consequently I don't need to trim up as much to get the nose up.
The only downside is that they aren't as fuel efficient as the vipers, with the vipers I was getting 0.78nm/litre, the rev4s get about 0.7nm/l. I was willing to make the sacrifice for the vast improvement to the boat, they really did make so much difference to the handling.
HTH

martini · 18 July 2012, 18:02

Ian,
I've got a 19" rev4 you could borrow except for the fact I'm using them at the mo as one of my 17"s is sh***ed.

In fact re reading your post if the 19 viper gives correct rpm's then the 17" R4 is probably a closer match. It's my 17" LH R4 that's gone U/S so the RH is available for a short period while I save up for a new LH

Pikey Dave · 18 July 2012, 18:05

Quote:

Originally Posted by martini

Ian,
I've got a 19" rev4 you could borrow except for the fact I'm using them at the mo as one of my 17"s is sh***ed.

In fact re reading your post if the 19 viper gives correct rpm's then the 17" R4 is probably a closer match. It's my 17" LH R4 that's gone U/S so the RH is available for a short period while I save up for a new LH

How bad is the damage? Steel Developments have fixed price repairs regardless of the extent of the damage. IIRC they will rebuild a prop as long as there is at least 50% of the original remaining, worth a punt.

martini · 18 July 2012, 18:05

Another one worth trying is a 19" Mirage plus. I've probably got one somewhere

Of course for either you'll need a flo-torq hub from Black Dog Marine

martini · 18 July 2012, 18:10

Quote:

Originally Posted by Pikey Dave

How bad is the damage? Steel Developments have fixed price repairs regardless of the extent of the damage. IIRC they will rebuild a prop as long as there is at least 50% of the original remaining, worth a punt.

There's a 1" crack at the base of every blade

Propellor Solutions (thought I'd give him a chance to redeem himself) were supposed to send me a special welding rod to have a bash with. It's hit & miss whether repairs like this work but I've given up waiting for the rod anyway, useless tw*t

Pikey Dave · 18 July 2012, 18:15

Quote:

Originally Posted by martini

There's a 1" crack at the base of every blade

Propellor Solutions (thought I'd give him a chance to redeem himself) were supposed to send me a special welding rod to have a bash with. It's hit & miss whether repairs like this work but I've given up waiting for the rod anyway, useless tw*t

I reckon Steel Developments would sort that for 89 quid

Chris · 18 July 2012, 18:20

Ian,

I ran a 19" Viper on TimeBandit and it was perfect. Great hole shot and good top end.

How high is your ventilation plate above the bottom of the transom? What is your top end speed and RPM?

Does it sound like the prop is slipping when you drop the hammer ?

Chris

Ian M · 18 July 2012, 18:44

Hi Chris,
Interesting! My experience is pretty much as PD's. Hole shot in particular is just terrible compared to many other RIBs that I have driven. With a 200 on the back of a 6.5 it should be much better than it currently is. Still I cannot shout too much until I have found a prop that performs better

Ian

Chris · 18 July 2012, 18:51

Something to consider is that with the 200HP E-tec which is the same block as the 150 & 175 they remapped to get the additional top end power however in order to do so bottom end torque had to be sacrificed.

Could explain why the 150 had such good hole shot.

Ian M · 18 July 2012, 20:15

Maybe, although when the boat is loaded I can get the prop to spin when trying to power up, for instance powering out of the trough and over the backs of waves is one particular time I can remember. I think the hole shot and poor top end is down to the prop, hopefully time will tell.

GordyP · 18 July 2012, 20:30

I changed from Viper to Apollo props, much better grip and about £200 cheaper as well.

buzzin hornet · 18 July 2012, 20:51

Guys

Sorry to ask a stupit question but could you explain what hole shot means, good or bad. heard this expression a few times and haven't a clue what it means

Cheers

Buzzin

martini · 18 July 2012, 21:01

Quote:

Originally Posted by buzzin hornet

Guys

Sorry to ask a stupit question but could you explain what hole shot means, good or bad. heard this expression a few times and haven't a clue what it means

Cheers

Buzzin

from wiki:

Quote:

This term can also be used to describe the starting performance of a vehicle. A vehicle that is fast off the line (though not necessarily fast overall) is said to have a good "holeshot"

Oscarguitar · 18 July 2012, 21:24

I have a Rev 4 19" and my understanding is that it is a stern lifting prop allowing you to plane at lower speeds. I struggle to get the bow up even trimmed right out but can plane at 10 knots. They work really well on heavier boats. Generally you can run them high, they have fantastic grip, rarely blow out and great hole shot. Not the best for top speed but good for cruise and better than most for manoeuvring.

However all boats are different and what works on my boat might be rubbish on yours. What ever you get make sure you get it balanced even if new. I tried a new 21" (higher top speed but WOT too low) and it felt like a blade was missing at 2300rpm.

Check out the hull truth forvlots of views.

Have fun

Ribochet · 18 July 2012, 21:47

Quote:

Originally Posted by buzzin hornet

Guys

Sorry to ask a stupit question but could you explain what hole shot means, good or bad. heard this expression a few times and haven't a clue what it means

Cheers

Buzzin

Hole shot a measure of boat/engine performance much like the 0-60 time quoted for cars.

It refers to the time it takes for the boat to get on the plane from dead stop at maximum throttle

buzzin hornet · 09 August 2012, 12:40

Cheers Guys

You dont ask, you dont get.

Ian M · 04 June 2013, 13:07

I could not resist the weather today, so I have been out prop testing. The conditions were just right; a slight chop to 'unstick' the hull, but nothing to cause me to back off.

The boat was originally provided with the engine set at this lowest setting. I was running a 19" Viper at one hole up from the lowest engine height. This is where the Viper seemed happiest and Mike Vincent has told me that the Vipers like to run 'high'. At this setting I saw 5900 max revs. On the basis that I had to start somewhere I bought a 21" Apollo of the same diameter. The first thing that I noticed is that there is a greater surface area to the blades of the Apollo.
I ran it at the same height and it ventilated some, particularly in the turns, but I could only pull 5300 max revs. I have now dropped the engine by one hole and the boat feels a lot better. No ventilating in the turns and I can really feel the boat accelerate, as opposed to just spinning up the Viper as it did before

. The numbers are still 5300 max revs, best one way speed 48.2 knots, with 43.5 knots on the return leg. This is a good 2 to 3 knots up on what I was seeing with the Viper. The tanks were almost full, 200+ litres, and one pax on board.
Before I go out and spend another £400+ on a 19" Apollo, does anyone think I should be looking at something different?

whisper · 04 June 2013, 13:51

According to Evenrude you reach your max 200hp at 5350 RPM

which is in the centre of the recommended Full Throttle RPM Range 4850-5850 tr/min

OSPREY RIBS · 04 June 2013, 16:19

Quote:

Originally Posted by Ian M

I could not resist the weather today, so I have been out prop testing. The conditions were just right; a slight chop to 'unstick' the hull, but nothing to cause me to back off.

The boat was originally provided with the engine set at this lowest setting. I was running a 19" Viper at one hole up from the lowest engine height. This is where the Viper seemed happiest and Mike Vincent has told me that the Vipers like to run 'high'. At this setting I saw 5900 max revs. On the basis that I had to start somewhere I bought a 21" Apollo of the same diameter. The first thing that I noticed is that there is a greater surface area to the blades of the Apollo.
I ran it at the same height and it ventilated some, particularly in the turns, but I could only pull 5300 max revs. I have now dropped the engine by one hole and the boat feels a lot better. No ventilating in the turns and I can really feel the boat accelerate, as opposed to just spinning up the Viper as it did before

. The numbers are still 5300 max revs, best one way speed 48.2 knots, with 43.5 knots on the return leg. This is a good 2 to 3 knots up on what I was seeing with the Viper. The tanks were almost full, 200+ litres, and one pax on board.
Before I go out and spend another £400+ on a 19" Apollo, does anyone think I should be looking at something different?

At 5300 RPMs the engine is "lugging" you should be looking to get 5600 RPMs minimum and no more than 5850 when normally loaded. (2 up, full tank of fuel)

You should have the ventilation plate on the e-tec set 2" above the bottom of the transom and fit the Viper 2 19" prop you should be good for 48 knots with the 200HP and this set up.

This is a proven set up on this boat / engine combination. I am surprised you had issues with the Viper as you stated it has always produced the best results on previous 6.5 meter ribs.

Drop me a PM with your phone number and I will have a chat with Mike Vincent tomorrow to see if he has a 19" Viper 2 you can test.