Engine tilt

**Papee** · 04-08-2008, 09:51 PM

This subject is still befuddling me. I can't really remember how my boat acted before. I have done so much work on it lately changing things like the rigging, new prop, more engine mods etc. Before, the boat seemed to be pretty level the whole time, it didn't seem to lift the front end, just stayed level and came on plane. Now it planes fine but it runs with the front end in the air. I think this is slowing my top end speed. Everything is different so I can't really compare tilt setting. I have a longer boat than most minis, 16ft so I can't understand the front end carrying so high, not real high just higher than normal or about level. I have about 3/8 in of shim in the front now, what is the most anyone has used to shim? I think that I could shim some more to bring the nose down and it would help the top end speed as long as the front end does not plow. Any thoughts on this?

Edit: This is in deep water btw, I usually don't run the deep water but right now the river here is about 4 feet higher than I normally run. When I am running between fishing spots I am normally in anywhere between just a few inches of water to maybe a foot or two.

**Randy Jr** · 04-09-2008, 08:50 AM

im sure you did but did you put your weight back on the front i remember you mentioning taking off your trolling motor and stuff.. I was also wondering the same thing if the tilt of your propeller would make any diffrence in the the way it drives because i have my tilted down a little towards the front of the boat... but i figured it wouldn't hurt much as long as it was pushing forward

**Papee** · 04-09-2008, 04:58 PM

It still rides like this Randy with the weight on. I was testing/fishing again today. I am convinced that I need some trim tabs but the only thing with the trim tabs is that the get knocked around quit a bit. When I drift while fishing sometimes We hit a rok or two with the back of the boat. You can't always see them coming up. A lot of times they are just below the surface. The only other thing I can think of is to try one of the horizontal "foils".

**Spyda-Ryda** · 05-22-2008, 10:51 AM

Dave what's the lateset on this? Personally, I would try to shim the motor at the mounts. That's probably the easiest and cheapest way to get results. And yes, shimming the motor up in the front or back does make a diference on how the boat rides. As long as you have clearance for the prop, you can shim it all you want. I'll actually be shimming up the front of my motor this weekend to stop the boat from hopping. My boat wants to start hopping after half throttle. In my personal experience with boats, the less amount of surface area that you have actually making contact with the surface of the water, the faster the boat will go. Unless your are just too heavy toward the transom and your bow is riding way up in the air.

**Papee** · 05-22-2008, 11:13 AM

If you look at a side photo of my boat you will see that almost 1/2 of the hull is rake. I think this is way to much. When tilting the motor, I believe that the more you push down on the front of the boat, the more speed you will scrub off. As with everything on a mini, I think that all these adjustments are important, finding just the right spot, trying to get everything you can from the setup.

**dr.peck76** · 07-23-2015, 01:49 PM

OKay Papee, I'm gonna get you to scratch your brain again. After reading through the threads I figure this is the best place to ask the question. I've been shimming my rigging and currently have about 3/8" of shim under the front. I don't think that really translates into anything though because all boats are different in where they mount and how long the rigging is. My boat seems to be running flatter but still porpoises at higher speeds. SOOO, is there an angle off of vertical (for the prop) that any one has found to be optimum? or a range of angle where most props are set?

I suppose we could use the difference of the prop shaft center-line angle compared to the boats floor as well. That may be easier to measure.... anyone have any thoughts on this????

**Corky** · 07-24-2015, 09:33 PM

Here's what I've found with months of research on all aspects of the prop angle...First up would be the balance of the boat in general...The concensus is{as a starting point} the finished boat should balance out around 1/3 the hull distance from the transom forward...So for an example a 15ft hull should balance out at 5ft forward of the transom.... The prop angle is set parallel to the hull bottom...

After the initial test run is where the adjustment comes in...Either by moving components around in the boat,changing the prop angle, or both if need be...How much the bow is porpoising or plowing is obviously the determining factor... There's really no magic number or angle that will work for every hull out there...There's just too many variables...

What you're doing is exactly how it's done...Keep adding shims until you get the bow down where it's a happy medium with all-around performance and planing....In a perfect world you'll hit the sweet spot and be done with it....

On a side note some of the bigger airboats just cant balance the components out to where it needs to be... In that case they end up adding a hydraulic, adjustable trim tab to the transom for the leveling/planing duties depending on how many passengers and/or equipment is loaded for the trip...The center,single trim tab is popular with airboat owners...We had a fishing boat that had the dual trim tabs with a joystick adjustment you could actually level the boat out from one side to the other as well as the height adjustment...

**Papee** · 07-24-2015, 11:27 PM

Yes like Corky said, every boat is different even if they are the same hull. It all depends on how your weight is distributed. You're adjusting to the surface that your boat runs on while on plane. This had me so befuddled I put on an adjustable front motor mount so I could adjust it while running the boat. I found out that it took more pointing at the water than I thought.

Its hard to go too far with this adjustment but it would start slowing you down if you start plowing. When I was testing this I went to extremes and shimed an inch at a time to see what would happen. Depending how the weight is distributed this could not make a bunch of difference.

It does get confusing as you see by my post. You have to do all your testing in the same water to be consistant. If you doing this is low water stay in that low water for all tests. Also adding to this, you need to have a hasty medium here, the boat will run different with someone up front.

You want to do this alone btw, you want to get the front end down but not to the point that it plows with a passenger onboard. I don't think you'll have a problem with this because they adjustments seem to be slight with your boat as were mine.

**dr.peck76** · 07-27-2015, 10:11 AM

Thanks Guys, on Thursday evening I put about 70 miles on the boat with a passenger. We traveled up river in varying conditions and started with a full tank of fuel. If you remember from my build thread I've built a fairly large tank (a little better than 20gal) Fairly heavy when full.(120lbs of fuel??) Anyway when we left the ramp, my buddy noticed right away that it was riding way flatter than last time he was along. I tried a couple high speed runs through the evening and by the time we were almost back, the boat would defiantly plow with the passenger up front and without the weight of the fuel on the rear. I'm thinking I've got it close enough not to bother with any further adjustments. Oh, and 35 MPH is as fast as this hull wants to go. It starts skating all over the place in shallow water around that speed. Not easy to control at all. It cruises very nicely at 24-26MPH though with lots of throttle left for emergency maneuvers if required. I haven't tried any full throttle runs by myself.....I might be able get a bit more out of it.....