Questions on performance

[ajochum]

Took out my new purchase today - my '82 18' 2+3 w/350/260hp and wondered how it performs vs. others out there. Today there were three of us and we were in very choppy water. Was only able to hit about 45 mph. Other night in calm water with just two of us, we did 52 mph with more to come - I just didn't dare first time out.

My question is - is this about par for an 18 ft.? I have a stainless 21 degree prop. Is there a better one that some of you might recommend?

Guess I'm greedy, but I'd like to see it hit 65 or so. Am guessing the weight of the people play a huge part, along with calm lake etc. but am looking to see what you might suggest.

Sure love this boat!!

[MOP]

little time to get use to the boat IE: Seat Time! You need to use some trim on the drive which take a bit of getting use to, when you hit 52 what was your RPM? And what is the make and model of the prop?

Phil

[ajochum]

Phil - My prop is stainless 3 blade and markings are SB9861 and also 48 89802 A4 21P. Nice shape. Boat is an 82 and only has 380 hours on it. Motor is really strong and is firing on all 8.

Wish I could tell you the RPMs - never think to look at that and will next time. I get the boat as flat as possible by moving the trim tabs all the way down and also get the prop all the way down. Have been told by the previous owner that I may want to try to actually move the prop up a bit once I get going.

Think I can do better? Is another prop a consideration?

You're right - those trim tabs are fun to get used to. Getting it level sometimes makes me feel like I'm going to lose control if I'm not headed just right into the wake.

[RedDog]

You are going about it backwards. For best speed you want to get the bow up - air it out.

Bring the tabs all of the way up and as you build speed start trimming the drive up. A little at the time to see how it does. You will be amazed as the speed increases as the drive rises. If it starts to cavitate then you have trimmed up too far.

If you get porpoising, then you have trimmed up to fa for the speed you are going. Trim down, increase throttle, trim back up a little.

Get back to us with the RPMs and GPS (not speedo) speed.

[BigGrizzly]

Welcome to the board, as for the prop get some serious seat time then get back to the prop. as for speed 65 with a 260 HP engine is dreaming, but you knew that. ifr the prop is wrong we maybe will get another 3 mph out of it.

[ajochum]

You are right - I sure had it backwards. It certainly makes sense - more boat in the water equals more resistance. Could you guys define "cavitate" and "porposing" for me - also GPS?

The guy I bought it from claims he had it to 62 mph.

Do you lose a lot of steering control with the front end way out of the water?

What a freaking fun boat - and to think I almost didn't buy it. Best part is my wife just loves it when I get into it a bit. I learn more about her (my wife) the longer I'm with her (35 years and counting)

[ky-donzi]

Welcome to the board.......Be careful if you are not use to the boat. They take a little getting use to..... It took me a whole summer to get use to the handling in some conditions... anyway

What I like to do it sorta what red dog said. I take off trimed all the way down and at about 15mph or when it starts to plane off adjust the TABS to level the boat. I typically find just adjusting one side a little make all the difference in the world. Now add more throttle and depending on your boat ....trim it up a little at time as you approach 45-50.... play wiht the trim until it cavitates.......( the motor revs higher but you stay the same speed or slow down) once it cavitates trim back down alittle.... Have fun

[RedDog]

You are right - I sure had it backwards. It certainly makes sense - more boat in the water equals more resistance. Could you guys define "cavitate" and "porposing" for me - also GPS?

The guy I bought it from claims he had it to 62 mph.

Do you lose a lot of steering control with the front end way out of the water?

What a freaking fun boat - and to think I almost didn't buy it. Best part is my wife just loves it when I get into it a bit. I learn more about her (my wife) the longer I'm with her (35 years and counting)


Cavitation - when the prop spins but isn't getting any "bite" in the water. Some props will be more prone to it than others. If it happens, you'll know it. To stop it you may have to throttle all of the way back and then start over.

Porpoise - that is when the bow bounces up and down. To stop it, trim in, lower tabs, or speed up. Or some combination of any of these. Some props are better than others at avoiding this.

GPS - "Global Positioning System." Most speedos in a boat are really inaccurate - they read optimistically. Particularly at higher speeds. A hand-held GPS will give a much more accurate speed indication. For boating, a GPS speed indication is considered gospel, although I think a radar gun is even more accurate.

Your steering will be fine at the speeds you're running.


PS - welcome to the world of Donzis. Make it to an event (look in the Events section of this board) and meet some great people.

Where do you live / boat?

[Pismo]

No tabs and big trim will buy you several mph. That is an old cleaver merc prop. Get a Mirage Plus.

[ajochum]

Many, many thanks for all of your input guys! Am getting an quick and informative education on 1) How not to kill myself or others in and out of the boat. 2) Termonology. 3) Patience.

I am from Western New York and boat on Lake Chautauqua, which is a 17 mile long lake near Lake Erie. Great lake for boating. I do plan on attending some events. It came with a fabulous trailer 1977 Baron out of Orlando, Fl). I would really like to attend the Lake George events that I have been reading about - especially the early Summer one. First I need a reliable tow-vehicle. Any other good events in the area I should be aware of?

I really had questioned how reliable the speedo was on the boat. In fact, my dumb brain can't quite figure out how it works. Prop speed? That would't seem too accurate.

So far I have gotten away with doing two stupid things on the boat that could have proven costly. (Dare I hint something about the hitch not locking properly on the ball :smash:and shallow water:shocking:). Anyway, lessons learned early on.

Will post after I try some of the things you all have suggested.

[ky-donzi]

Most factory speedos work off of water pressure measured at the transom or the drive. The faster the boat moves across the water the hard the water is pushed up a tube into the speedo.

Might wanta get a deepth finder,,, not much money and if you are not faimiliar with the water could be a real cheap insurance

[ajochum]

This probably isn't related to anything - but when we sat idling in the water in the middle of the lake (having drinks) a slight mini roar or sound came out of the front of the hull. My wife questioned what it was. I couldn't imagine as there is nothing up there from what I can figure. Ideas?

[maddad]

Because of the way these boats are built, whatever is going on under the hatch will be heard from near your feet.

[blackhawk]

As others have said as you get used to the boat you can bring the tabs and drive up which will loosen the boat up for more speed.

FYI...the prop losing bite because of surface air(or exhaust) is ventilation not cavitation.

[Carl C]

All good advice and driving tips here that I agree with. You're a little down on power now but your boat can easily top 70 mph; How much money do you have?:eek!:

[ajochum]

Carl - Wish I had the money to drop into my boat what you have in yours! What are you running? Unfortunately, my next spend is for a boat lift to keep it pristine for a future show in Lake George.

[BigGrizzly]

I jump in here Carl doesn't spend much on his boat, He is very careful with his $ except in the lab finished Bravo 1:wink: As for the boat lift I have a Hydrohoyst and personally would recommend it over engine mods any day. I use to live on the Jersey shore and boat was in the water all season - bottom pained but still not a lift.