Prop testing 15 feet boat with Evinrude 140

[Gammabusa]

Hello all,

time for some test runs again.Since I added a lot of speed by sharing and getting advice from the great guys on this forum with my last boat I will post what I find here and hopes to get some input.


Boat is a 1987 Norvegian boat called Gromling 450(15 feet) and engine is a 1980 Evinrude 140 with Boyesen reeds and Bobs nosecone kit with low water inntake.It is mounted on a CMC hydr jackplate and at full height the prop shaft is same height as bottom of boat.

Most possible speed is what I am looking for.Bottom of boat has no pad but rounded V all the way.

http://home.online.no/~jmarpede/aGromling Motor 14.jpg
http://home.online.no/~jmarpede/aGromling Motor 24.jpg
http://home.online.no/~jmarpede/aGromling Motor 45.jpg
http://home.online.no/~jmarpede/aGromling siden 002.jpg
http://home.online.no/~jmarpede/aGromling oppi framme 045.jpg


TEST 1 22 Raker:

Got it to max RPM 6500 on the omc tach and GPS speed of 59,3 mph with engine at max height and three short push on the trim out, if I tried to trim more the boat started chine walking to much and I did not gain any RPM so my guess is that 6500 is enough for this old engine.Ok result but I feel it is to much slip at around 11-12%??

TEST 2 24 Raker:
Got it to max RPM 6200 on the omc tach and GPS speed of 59,5 mph with engine at max height and two short push on the trim out, if I tried to trim more it got to wild for me to handle.

With engine all way down i got it to 57,8 mph at 5700rpm with a bit more trim but went crazy if trimmed to much.

Max trim I am speaking of here is half an inch on the trim cylinder so really no trim at all.My guess is that I have to find a way to stabilize this boat before getting any more speed so no I am thinking of making some sort of pad under it.......

 

[Ron G]

Re: Prop testing 15 feet boat with Evinrude 140

Hey bud.im going to asume you got it balanced?with some shot?or plates.if not you may want to try that also.good to see ya posting again!

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Nice to hear from you Ron,

dont really understand what you men with shot?? Plate you mean smart tabs ore anything like that?

I really dont understand what is wrong with this boat/setup, my earlier boat was from same constructor rated max 35 hp, this is one feet longer and rated 90hp and is much worse when exeeding 55mph, it is like the boate hate me and want to kick me of......huh, hehehe

 

[LubeDude]

Re: Prop testing 15 feet boat with Evinrude 140

Hey:

I've messed with set ups on Bass boats quite a bit so here is MHO. [My Humble Opinion].

It's your hull, you have no pad for the boat to get up on. Thus the boat rocks from side to side at high speeds. Your only option, again, MHO, is some kind of tabs like Smart tabs. In this case, I would not put them all the way out like they are designed to be installed, but in a bit closer to the engine so that they are not out of the water completly at WOT.

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Okey, thanks, that make sense, after testing all day today with weight front, weight rear and up down out in with engine I think that is the next on the to do list.Same what I do when getting up to 55+ it is getting unridable for me.

 

[Ron G]

Re: Prop testing 15 feet boat with Evinrude 140

Shot is lead weight to balance the boat with the driver and such.LD thoughts with the trim tabs is a great idea!i dont know much about tabs at all but seems like they would make a great way to keep some sort of balancing.good luck and let us know what happens.and stay dry!!

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Okey Ron, still dry.....

have added something called Roca speedrails http://www.ocke.se/industrial_designs/index.html#rail
on my boat and now and is a little better and it is kinda controllable but has not really tested with my Raker 24 cause windy weather, it is still chinewalking but I am able to controll it with my Raker 22 to max speed 60mph at 6500-6600 rpm, tach bumping, my engine wont rew any more.....where is Dhadly these days?? I could need some couple hundreds more rpm.

Anyone know how high it is possible to jack up the engine before it gets dangerous. My jack is mountet so that propshaft is at bottom height at max height but have no problems with grip with my Rakers so maybe I could get the lift higher?? have to do some work on the transom cause my upper bolts cant get any higher thant they are now.

Anyone??

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Nobody has any ideas how high is it possible to raise the engine?

I know it is different from boat to boat, propeller and so on but has nobody any idea how high the highest V bottom/ padded bottom they have ever seen was..??

Thanks again....

 

[walleyehed]

Re: Prop testing 15 feet boat with Evinrude 140

You have 3 controlling factors with heigth...1 is water pressure 2 is prop choice and 3 is handling issues.
I've been through what you are trying to do and #1, unless you can exceed 70mph, the bullet-style nose cone will hurt you in most cases.
#2, Mobster tabs are the only items that have enough area to stabilize that boat above 55-60.
I'd keep going up until handling becomes a serious issue or venting begins....considering a low-water pick-up, pressure shouldn't be an issue.
You may also think this sounds dumb, but I would recommend a chest protector and brain bucket. Mark this in your book-"If you continue to have handling issues, you WILL need this equipment."

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Thanks for answering Kenny,

I have Bobs nosecone with low water pickup and seems almost as higher I get the engin, higher is the pressure, it reads 25 psi at wot on my OMC gauge engine at max height.

I mounted the hydraulick jackplate in the old engine holes and when max height prop shaft is even with bottom but has no problems with spinning/cavitation, it is when I start trimming the fun starts,bump, bump,bump.....

Just woundering if it is worth the work of raising the jack on the transom, has to build up the transom to get somthing to put the upper mounts in....

I have full MX protection gear so if it is getting to wild I may start to use it..??

 

[walleyehed]

Re: Prop testing 15 feet boat with Evinrude 140

If you are at the height that the gearcase is riding half in/half out, that may possibly be some of your handling issues.
The gearcase has enough surface area that when on the surface, it doesn't know whether to dig, dive, climb, etc....you "may" be at the point that a very slight change will make the gearcase itself want to plane, or...possibly dig.
I hope this makes sense as the gearcase normally has both the top and bottom of the cone "in" the water, the climb of the bottom side is counter-acted by the dive of the top side, so if you're getting that cone to the point the top is loosing the ability to counter the climb, I'd expect a wild ride.

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Thanks again Kenny, that make sence, when I raise the engine step by stepp it is somthing happening back there and is possibly what you describe, somtimes when I am able to controlling it it is like it is changing gear and the boat gets very "loose", feels like i have changed to a different propeller, I only manage to drive it a couple of seconds in this state and then it gets wild and want to throw me of.

LubeDude and you have mentioned smarttabs so will try it next, mobster is impossible to get here but has sent mail to the producer in USA so will see what happens.

Thanks!!!!!

 

[Ron G]

Re: Prop testing 15 feet boat with Evinrude 140

All i can say is dang!!!you got her screaming!!what kenny said makes sence!im surprised she hasnt blown out yet at that height.Kennys right about the safty equipment you need to wear all you an.cause if it blows and hooks on ya its going to be really wet ride.also one other thing to think about your prop is surfacing big time so make sure after every run you dont have any hairline cracks in it.maybe time to start looking for a prop made for what your doing.good luck and stay dry!!

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Well,
only smart tabs I got in a hurry over here was smart tabs SX, they did what they are supposed to do but when reaching toppspeed the boat is chinewalking like before so if I dont find a padded boat over here I will try to build a pad during this winter, I found lotsa Pad pictures over at the Hydrostream club site so have somthing to " copy "

Yes I know you said it before, PAD is the way to go....

Thanks

 

[Dhadley]

Re: Prop testing 15 feet boat with Evinrude 140

The best way to stabilize the ride is to buy my Hydrostream Valero YT. We know it's stable thru the mid 90's.

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Well Dale,
maybe your boat ends up in Norway, we will se what happens but I have a plan.....

 

[Frank Acampora]

Re: Prop testing 15 feet boat with Evinrude 140

You may want to try some aluminum angles at the hard chines at the transom going forward about two to three feet long. They grab the water that squirts out the sides and re-direct it down thus helping to stabilize the hull. Haven't tried it myself yet but I have a 14 foot flat bottom with a 90 that is just begging for a 125 or 140 and those angles. Does 56 right now with a 21 pitch prop at 5600 rpm. That's it in the avatar

 

[Gammabusa]

Re: Prop testing 15 feet boat with Evinrude 140

Thanks for info but I am not sure if I know what you mean but I have mounted two aluminium list under my boat, helped abit but it still chinewalks

Looks like fun........