First outing....I have questions

Snowmastiff · 17 June 2018, 07:45

OK. Thanks Gents for all the info I have enjoyed and benefited from all Winter. Now I have my boat, a 14ft SIB (Inmar) - that is 4M I believe, and with a 25 hp Suzuki. Will be in Prince William Sound in July for a Small 8 mile trip up Passage Canal. Have been learning a ton in local lakes to prepare. Here is where I am stumped.

1. When I get to speed (just me and my two teen daughters, little gear) on a plane WOT I have had the experience of feeling like we have run over something. A big bump, throws us up it feels. First time I really thought I had gone over a log or something, but no. Girls thought I hit an animal, that’s the feel. Not hitting anything. Quite frightening actually. Floorboards kinda rumble and the bow kicks up violent like, but all is structurally sound. Stringers holding joints, floor not buckling. What the heck is going on? Has happened several times. Flat calm, maybe a ripple on the lake. Doesn’t happen every time, but enough to make me not run at speed often.

2. My engine is throwing water in the boat at WOT. Normal? The kick back from the propeller is somehow throwing in the boat. While I sit on the tube to throttle I’d just get soaked from the kickback. Have tried various tilt action on motor, all does the same.

3. One more please. I try to tilt up a bit to play with trim, but when I get to speed the tilt is lost. I can see the engine gradually dig back in, losing my tilt, even though I have locked in place. What gives.

First boat. Having a blast. Be gentle, but shoot me some information please. What am I not getting on these ones?

Last Tango · 17 June 2018, 08:51

1 & 3.....

Don't confuse trim & tilt.

Only the bottom part of the movement on most engines is actually "trim".
Beyond that is "tilt". Could it be you're trimming way out into the "tilt" part of the movement and the "thump" you feel is the engine dropping back to the "trim" part when you throttle up.

I'm not familiar with your engine but most larger engines will drop back to their maximum "trim" position if you push them beyond a hard idle if their tilted too far out. This is both for safety and to protect the engine from damage.

spartacus · 17 June 2018, 09:38

1/ Sounds like the boat isn't up to pressure and you're displacing water rather than planing. Not familiar with Inmar inflatables, but you mentioned stringers, so assume build is similar to Zodiac. The inflatable keel on Zodiacs MKII (4 meters) is 220 millibars and the sponsons were 220-240 millibars. There's no way the floorboards should 'rumble'. Double check with a pressure gauge, especially in the water as ambient temperature and the water temperature all play a part.

2/ With the boat out of the water, check the anti-cavitation plate is horizontal in line with the keel.

3/ I used to run a Zodiac MKCII (13'6") with a Yamaha 25hp. The engine was 2-stroke and manual start and tilt. In all the years I was running it I rarely tried to move the adjustment on it. It was set on the second hole away from the transom. With 3 people on board I doubt you have the horses to see any benefit from adjusting trim.

Anyway, see how you get on.

Fenlander · 17 June 2018, 11:55

Hello and welcome to the forum.

It would help to know which Inmar model you have... the leisure or pro type? Does it have a sectional wood or alloy floor?

Re the outboard do you know if yours is the correct shaft length for the transom? Is it a new type Suzuki 25hp 4-stroke?

Mikefule · 17 June 2018, 13:17

That's a moderately large SIB with what sounds like a light crew. One possibility is that air is getting under the bow and lifting the boat, then then it is slamming back down. My gut feeling from your description is that your engine is tilted too far out, which will tend to squat the stern and raise the bow and make make handling a bit squirrely.

The other thing to consider is that in any given set of conditions (sea state and direction, wind force and direction, weight of crew and equipment, weight and power of engine) there is an optimal maximum speed. Flat out is not always the best. Just because you've got a few revs left in the throttle, doesn't mean it's always the best idea to use them. Back off a bit and the boat may settle.

But first, look at how far out/down the engine is.

Snowmastiff · 17 June 2018, 18:22

Thanks so much:

Fenlander - It is a 430 Mil Inmar. Aluminimum floorboards 5 of them plus the bow. It is a short shaft 4 stroke, yes the boat requires short shaft.

Last Tango - Right. I see I need a vocab lesson. I thought tilt refers to how down or up I raise the prop in the water. I thought trim refers to how low or high the bow is riding. I’ll study up on the forum a bit more.

Spartacus- What is VAT? Good point on the pressure. I will check. It has over inflation relief valves and my guy said I don’t really need a pressure gauge. Just bring them up to tight with foot pumps to 3.5 psi. But the foot pump gauge seems silly. Can’t really tell what I’m at. I’ll get a decent gauge. And I haven’t messed with anything on the motor. Don’t know what an anti-cavitation plate is. I see I am using the word tilt wrong and throwing in some confusion. I was just referring to raising the prop or lowering the prop up and down. I still get water thrown in the boat no matter how I angle it. And - the motor won’t stay angled where I put it.

Mikefule- Thanks for that. Yes , ease up on the throttle may be the best idea. My 16 year old is having a blast and always wants faster - but I want safety and answers.

Thanks again guys. Incredibly responsive and helpful.

Last Tango · 17 June 2018, 19:16

Quote:

Originally Posted by Snowmastiff

...... - the motor won’t stay angled where I put it.......

How exactly are you adjusting this.....

Does it have power trim and the hydraulics are dropping or are you relocating the bracket pin of a manual trim system. If you have power trim the engine will only stay out to the maximum limit of the trim. Lifting it higher than that takes it into the "tilt" range and is only for lifting the prop out or nearly out of the water for mooring/trailering or for manoeuvring at very low speed in shallows.

If you're moving the pin of a manual tilt engine, the engine can't drop back down because it is limited by that pin. When the manual system is fully tilted there will be a latch of some kind on the bracket to hold it there but the engine can't be run in this position.

Maybe some photos of the engine tilted up would help.

spartacus · 17 June 2018, 19:29

Quote:

Originally Posted by Snowmastiff

Spartacus - What is VAT? Good point on the pressure. I will check. Don’t know what an anti-cavitation plate is.

It's just my signature - ignore it. In the UK we're paying 20% tax on purchased goods straight to HM Treasury so they can squander it!

Good news about getting a gauge. A foot pump doesn't really give you a proper reading.

The anti-cavitation plate or correct term is anti ventilation plate is on the outboard and stops air being drawn down down to the propeller. This diagram illustrates. You want the keel and anti ventilation plate to line up, give or take 25mm.

lightning · 17 June 2018, 20:22

I had the issue with water splash back at WOT and it turned out the engine was too low on the transom.
There was no adjustment so l put a 1/2” thick block of wood on the engine mount to raise it and that stopped the splash back completely.

Zodiac 2.85s with Tohatsu 9.8

SixtyNorth · 17 June 2018, 20:36

Re. point 1... I suspect the tubes and keel were not up to pressure. Was the water cold and did you top up the pressure when the boat was in the water? I have experienced similar issues with a 4.2m Zodiac late in the evening when the air temp. dropped and the water was rough, the pressure had dropped enough to allow the boat to flex and lose some rigidity.

Fenlander · 17 June 2018, 22:19

Lots of the points covered by the guys above. Having looked up the website for your boat at its size... with an alloy floor and weighing 235lbs if shouldn't suffer any of the odd problems seen with the lighter weight air floors.

I would add to the chorus of folks saying pressure is crucial so when you get a gauge you can trust that will be sorted.

I have found with SIBs they usually go acceptably well in the outboard's middle trim position so that's a good start point.

Re the splashback not usually an issue with your type of sib but as others said check the cavitation/ventilation plate relationship with the bottom of the transom and report back.

Snowmastiff · 18 June 2018, 03:31

Yes, absolutely cold water, and no I have not been topping off on water. Maybe that is the easy answer. I’m going to get a decent gauge and start paying better attention to pressure.

No, Last Tango, I’m not moving pins or anything. No haudraulics, manual,tilt. So I should not screw around with the tilt aside from docking or beaching or trailering? I was thinking that a bit of tilt would fix my water splash issue, but it did not. I raised it a little, locked it, but then it lowered back down when I gave good throttle.

I will be back out in a couple of weeks to play with all of these suggestions. Thanks again for all the advice and education.

Last Tango · 18 June 2018, 08:38

Quote:

Originally Posted by Snowmastiff

..... I raised it a little, locked it, but then it lowered back down when I gave good throttle.....

How did you lock it? Did you move the trim pin out to the next hole?
Because that's what sets the trim angle of the engine. It can be done with the boat afloat but generally the trim pin is under the water and it's a bit of a bugger to get at and see what you're doing. Normally best to try setting it when the boats on the beach (or trailer) and give it a try. The engine can only drop down as far as that pin.

Fenlander · 18 June 2018, 09:22

>>>No, Last Tango, I’m not moving pins or anything

I think we might be getting somewhere if the OP is raising the OB to the tilt/shallow water positions rather than trim pin setting.

By chance last night I was coming into the slip having tilted one notch for shallow water a little way out... and when I had to grab a bit of throttle I was reminded just how much bow lift and what a water fountain that produces.

Poly · 18 June 2018, 16:29

Quote:

Originally Posted by Fenlander

>>>No, Last Tango, I’m not moving pins or anything

I think we might be getting somewhere if the OP is raising the OB to the tilt/shallow water positions rather than trim pin setting.

Indeed. That potentially is linked to all 3 issues the OP describes. If he was in the UK I'd suggest he goes and finds an RYA centre that teaches PB2 and ask to bring his own boat along for part of the course. I'm not sure how Powerboat Training is structured in the US.

So assuming the engine looks a bit like this:

Notice those 5 holes that are in an arc/diagonal at the bottom of the transom bracket?
Notice you have a pin in one of them?
You adjust the trim by moving the pin between the holes. You move the pin by straightening out the end shown in the picture - which may require you to push it from the other side to get some slack.
HOWEVER - BE AWARE this pin is supporting the weight of the engine, if it falls on your fingers it could do serious damage.

That pic shows it currently in the lowest position - as Fenlander suggested go for the middle hole to start experimenting.

It sounds like you have found the tilt lever and "lock" which are probably on the other side or front of the engine.

brveagle · 18 June 2018, 18:21

I used to have similar issues as well with the whole boat moving around. I also used the foot pump until i thought it was hard. Then i went and bought a pressure gauge and i thought it was faulty because it wasn't evening showing 1psi.

I then went and bought a bravo 12v pump. Set the dial gauge to 3.4psi and wow did my boat transform. Suddenly the gauge "worked". i.e. it worked all along.

So my recommendation is to properly inflate your tubes and then set your motor height correctly.

pagick · 19 June 2018, 15:39

Electric pumps with set pressure cut off are great. Get one.
As for the waterfall coming under the motor mount. As many have said, play with your engines mounting height. And different motors vary a hole or two. My 4 stroke mercury was 2 holes higher than my E-tec
My Futura has a mounting height for 25 mph and less and one hole lower for full speed 30-37mph. ( speed tubes lift the boat 2") This week I have a trip with two fixes Ill try out. The easiest was a 12mm thick neoprene strip glued to the underside of the tilt tube part of the outboard. It should work at stopping the water. It is just thick enough to fill the void. If that fails plan "B" is to also install a 3mm thick stainless sheet metal I fabricated to created a diverter that blocks most of the water from hitting the blunt part of the shaft when running slower. It mounts to the transom bracket and installed with heavy duty wire ties. Easy to install in the water if its needed.

Snowmastiff · 20 June 2018, 09:30

You guys are terrific. I’m going to need to send in my 20 bucks I see for a proper membership.

Looks like the pin is set to the first (or last setting). I tried to upload a pic but ran into an error. Do you suppose moving it to the middle might help with my backsplash issue? I can do this on my own yeah? With rudimentary mechanical skills? Don’t need to have my Suzuki guy do it? Just a few YT vids?

I’m on Amazon right now looking for the bravo pump. I think pressure and getting this tilt figured out is what I need to do.

No trailer, so me and my teen girls inflate and deflate each time. The pump will speed things up and set the correct pressure. Brilliant.

Thanks to all for the speedy assistance.

Fenlander · 20 June 2018, 09:47

If you mean your pin is in the hole furthest away from the transom this will encourage bow lift and water to be thrown up by the prop.

Start in the middle and report back.

Snowmastiff · 25 July 2018, 06:31

OK here is the update.

Moved the pin to the middle hole. Much better on the splash back, all but eliminated the water being thrown in. My pin was in the hole closest to the transom, so moving to the middle one has significantly raised the bow. No problem when I have my two daughters and a lot of gear, but I imagine I need to move the pin back if I plan to go solo?

Have been much more conscious about pressure in the tubes. No electric pump still,but drum tight and adding air after it sits a while in the cold water. Have not had that frightening rumble I reported on, must have been under inflated tubes.

Had a grand, and most importantly, safe outing with my wife and two teen daughters. Went out of Whittier, AK, about nine miles to a small cove in Passage Canal where there is a Public Use Cabin. Spent three nights there and spent the day cruising around looking at glaciers and wildlife. Crazy beautiful, and from the intimate view of a small inflatable you really experience the wildness of the scene. Of course it helped that we had unusually perfect weather, but it made boaters of us all.

Really appreciate the help from this site. Swear to send in my 20 bucks - just need to argue with PayPal for a little longer.

Cheers