Outboard Engine Angle

[bandit790]

How do you know what the right position angle is for your outboard motor? Is a perfect 90 degrees right or is another angle more appropriate?

 

[jtexas]

Re: Outboard Engine Angle

The ideal angle (call it "trim") will vary with the boat's speed. When you first apply power the bow will rise, you want to be trimmed in (gearcase closer to transom) to compensate. As the motor pushes the boat up onto the bow wave and the boat starts to plane, you want to trim out - to get as much of the boat and the lower unit out of the water as possible, reduce drag, better performance.

Manual trim, set it for the best hi-speed performance (trimmed out)...then if you want to improve hole shot, move it in one hole at a time until you get your best blend of acceleration and top speed.

 

[bandit790]

Re: Outboard Engine Angle

The ideal angle (call it "trim") will vary with the boat's speed. When you first apply power the bow will rise, you want to be trimmed in (gearcase closer to transom) to compensate. As the motor pushes the boat up onto the bow wave and the boat starts to plane, you want to trim out - to get as much of the boat and the lower unit out of the water as possible, reduce drag, better performance.

When you say "trimmed out" what is the best angle to start experimenting at (ie. a little bit more or less of 90 degrees or right at 90 degrees)? Thanks.

Manual trim, set it for the best hi-speed performance (trimmed out)...then if you want to improve hole shot, move it in one hole at a time until you get your best blend of acceleration and top speed.

 

[jtexas]

Re: Outboard Engine Angle

Is this the 135 from your other post? No power trim?

What's the hull length, width and design? Aluminum or fiberglass?

Is there a setback or jackplate?

Do you have a tachometer?

 

[bandit790]

Re: Outboard Engine Angle

Is this the 135 from your other post? No power trim?

What's the hull length, width and design? Aluminum or fiberglass?

Is there a setback or jackplate?

Do you have a tachometer?

Yes, it is. No power trim. I have a 20' fiberglass deck boat that is 88" wide. I'm not sure what a setback or jackplate is. If you're asking what the motor is attached to-it's on a fiberglass transom/swim deck. Now that we're on that subject, I'm kind of worried if the motor is mounted too low because the back part of the motor hood gets wet (underwater) while the boat is accelerating but is out of the water WOT and at idle. Is this normal?

BTW-sorry for so many darn questions, but the choke plates appear to be operating correctly and I still haven't figured out why I have no WOT. If it's an ignition problem-would I have a noticeable miss?

 

[jtexas]

Re: Outboard Engine Angle

A jackplate let's you adjust the height of the motor on the transom - a setback is just a bracket between the boat & motor.

There's a trade-off between top speed and "hole-shot", which is what we call the process of climbing up out of that hole in the water onto the crest of the bow wave. You want to lift the stern for hole shot, but you need to lift the bow for best high-speed performance.

First check the height of the motor: with the lower unit parallel to the transom, the antiventilation plate should be between 0" and 1" higher than the keel. The exhaust relief ports on the back under the powerhead need to be clear for cranking and idling but it's no big deal if they submerge during acceleration.

I'd start with it in the third trim hole out - it's just a trial and error process. A big boat like that without power trim, you're a good candidate for nauticus smart tabs, or maybe a hydrofoil.

http://www.nauticusinc.com/smart_tabs.htm

But first you have to make sure your getting all you can out of the motor. Let's continue that issue in your other thread, for continuity, so the whole iboats brain trust can get involved - there's more better minds than mine around here. 8)

 

[tashasdaddy]

Re: Outboard Engine Angle

bandit take something straight and long enough to go about 3 feet under the hull out to the engine, place this againts the hull , the AV plate should be higher than the top of the straight edge, probably 2 inches. if it is not the the engine is too low, and this will effect the engines performance. how far does the engine set away from the bottom of the hull it's self.

 

[bandit790]

Re: Outboard Engine Angle

bandit take something straight and long enough to go about 3 feet under the hull out to the engine, place this againts the hull , the AV plate should be higher than the top of the straight edge, probably 2 inches. if it is not the the engine is too low, and this will effect the engines performance. how far does the engine set away from the bottom of the hull it's self.

OK, this may be a stupid question but what is the anti ventilation plate?

 

[Paul Moir]

Re: Outboard Engine Angle

The large, flat, horizontal fin just above the propeller. Usually called the anti-cavitation or cavitation plate, though anti-ventilation is the correct term.

 

[bandit790]

Re: Outboard Engine Angle

The large, flat, horizontal fin just above the propeller. Usually called the anti-cavitation or cavitation plate, though anti-ventilation is the correct term.

Thank you. I will check that out tonight.

 

[wilde1j]

Re: Outboard Engine Angle

This isn't all that complicated. Adjust kick out until bow is a little loose @ wide open throttle (WOT). You should get a little porpoising, then back off one hole. That's it! Since you don't have trim 'n tilt, it's going to be a compromise, so do it with a normal boat load situation.

And get the motor height right first.

 

[Texasmark]

Re: Outboard Engine Angle

Hey guys, he's talking about a deck boat and I am assuming he means Deck Boat brand, (no offense) but a big fat tub. The bottom is mostly flat and there is a small area up front (about 1' of length) with a vee. It's a fishing boat made to carry around a lot of folks and fish.

Planing that kind of boat out is like planing a flat board. I don't think he wants his engine up like you guys are talking about because of the mass of the hull he will probably ventilate excessively on hole shot.

I think his current 90 degree angle is about as good as it gets (for that boat type). And if he wants to play around and experiment, he can move his tilt pin in or out if he wants to.

Now if he wants to do all the great stuff mentioned, he should get some PTT and put it on a high perf hull and then have fun.

My 2c,

Mark

 

[tashasdaddy]

Re: Outboard Engine Angle

bandit you need to clairify what it is, make model and year. Mark he said the motor is mounted to the swim platform. this leads me to think hes has the recreational deckboat, like hurricane, 4 winns, chapperal. bandit what do you have?

 

[bandit790]

Re: Outboard Engine Angle

bandit you need to clairify what it is, make model and year. Mark he said the motor is mounted to the swim platform. this leads me to think hes has the recreational deckboat, like hurricane, 4 winns, chapperal. bandit what do you have?

It's a 1988 Ozark Crappie Cruiser (see attached pic).

 

[bandit790]

Re: Outboard Engine Angle

bandit you need to clairify what it is, make model and year. Mark he said the motor is mounted to the swim platform. this leads me to think hes has the recreational deckboat, like hurricane, 4 winns, chapperal. bandit what do you have?

It's a 1988 Ozark Crappie Cruiser. I'm sorry that I don't have a picture available, but it looks kinda like a tri-hull.

 

[bandit790]

Re: Outboard Engine Angle

bandit you need to clairify what it is, make model and year. Mark he said the motor is mounted to the swim platform. this leads me to think hes has the recreational deckboat, like hurricane, 4 winns, chapperal. bandit what do you have?

It's a 1988 Ozark Crappie Cruiser (see attached pic).

I was able to find these pics. Hope it helps.

 

[jtexas]

Re: Outboard Engine Angle

that attachment feature doesn't work.

to post an image, join a free pic-hosting service, I like http://www.photobucket.com

upload your pics according to their directions, then from your album display page, copy the text from the box as indicated below, and paste it into the reply form.

 

[bandit790]

Re: Outboard Engine Angle

that attachment feature doesn't work.

to post an image, join a free pic-hosting service, I like http://www.photobucket.com

upload your pics according to their directions, then from your album display page, copy the text from the box as indicated below, and paste it into the reply form.

OK, let's try that:

 

[Texasmark]

Re: Outboard Engine Angle

I'd say that angle is about perfect to maybe one more notch out. A 135 on that hull ought to run out a good 35 easily. With the motor set back that far, under plane is going to cause you a lot of drag (lower unit is going to be deep) so I'd keep her either putting around or up on top, none of the 15 mph range stuff.

[That's still a good flat(tish) hull that should plane out nicely.] I think if you are having problems it's what I said. Get her up and on plane and go.

HTH,

Mark

 

[tashasdaddy]

Re: Outboard Engine Angle

that boat ought to fly with a 135. you are going to have to get hte engine height right and trim