outboard motor setup

[den001]

hi.

ive just finished re building my boat completly and have fitted a 1992 175 black max to a 17 ft seafarer vermont...

im pretty sure that it needs some fine tuning regarding positioning and propping... its sorta all over the shop and it sounds like the motor is really working, it planes easily but looking at some u tube clips, other motors sound much much more snappier..

my prop is a 21p


at the moment i get a maximum of 5000-5100 rpm at WOT, and it travels just over 85kph at this speed... i read on the net i should be sitting near 6000rpm at WOT

the cav plate is around 40-50 mm under the water on WOT and on the plane...

sometimes i have medium lean whilst accelerating to the left

steering is slightly tighter turning one direction in relation to the other...


any help please??

cheers
denis

[Jabba_]

my prop is a 21p


at the moment i get a maximum of 5000-5100 rpm at WOT, and it travels just over 85kph at this speed... i read on the net i should be sitting near 6000rpm at WOT

the cav plate is around 40-50 mm under the water on WOT and on the plane...



You need to raise the motor up at least 60mm so that the cav plate is just above the water when your at cruise speed..
I have a 2004 Vermont and my Evinrude cav plate is 60mm above the line off the keel...

Because your motor is so low, that is what is causing your boat to lean left and its also slowing your boat with the extra drag caused by the cav plate dragging through the water...

Depending on wheather your cruising, hard on the throttle or backing off, you will never have a balanced steering, it will away be heavier to turn in one direction then the other.. But by lifting the motor it will lighten the weight on the steering wheel..

[den001]

Thanks jabba. I will raise it two holes tomorrow arvo. Hopefully it will fix the teething issues.

I will try to get away with the 21p prop for now. Or should I try the 19p?

[Nathan Tuskes]

get the height sorted first before playing with prop sizes is always the rule mate

[Jabba_]

Nathan is correct... By what you have described, your motor is way too low.. I would guess that your motor is sitting on the top hole (#4).. If so raising your motor 2" or 2 holes, will only be just enough.. By all means try it, but I also try it on the bottom hole (#1)that will raise the motor the highest...

Once you raise the motor you will gain rpm and speed.. Its hard to tell over the internet how much rpm you will get on your rig cause the motor is so low in the first place. But if I had to bet I would say you will pick up 700rpm....

dont play with the prop untill you get your height sort first..

[Lancair]

The leaning is caused by the trimming of the motor.
I learnt sooo much from my Etec40 Tiller steer tinny. If its trimmed in too far you will have massive forces trying to turn the motor one way, to the right, because you hold this turning force straight, either by wheel steering or tiller, the force is applied as a lean to the boat. I can still prove this with my bigger boat with non feedback hydraulic steering. Same reason as to why a mono hull leans into wind. The wind is trying to force the bow downwind, the slight turning force needed to hold the bow straight results in a push to the bottom of the skeg causing the lean into wind.
When trimming my tiller steer, it was clearly evident when the right trim spot for the speed and load was found, as the steering became so neutral, I could let go of the tiller and it would stay dead straight, out of trim, either way too high or too low caused the tiller to wander. Having the trim too high was never really a problem because you get ventillation of the prop before any forces become evident.
If the motor is mounted too low on the transom, finding the high point in trim will be a LOT harder, if you can at all. As others have said this also increases drag.
You have a LOT of motor on that 17' boat.

[Fed]

It's nice to be in tune with your boat Lancair it always makes me laugh when someone says they fitted NFB steering and no longer have to hold the wheel with 2 hands.
There's a lot of boats out there crabbing like '62 Falcons.

[den001]

thanks guys..

the motor is mounted on the centre holes but it cannot go any lower. so i will raise it 2 inches and i guess it will have to be it... i have 2 holes i can raise it

[Jabba_]

If you need to go higher, you use an offset plate.