bowtie89

Well it started off really well. My first time out on my new boat but when we got out on the water and I dropped the hammer the rpms came up to 4800 and the speedometer only read like 34 can that be right the boat is a formula 206ls with a 350 magnum I am not sure of the prop. It was calm so I can not be sure if it felt like we I was going fast. I am not sure of the prop pitch and size but my father said that rpm is problably right. what do you think??? and then pulling the boat out of the water the drive wouldn't come up so we had to tie it up I have to find out where all the fluid went. Soo over all a thumbs up considering I had the engine out and the transom off!!! So far I am pretty happy with it and already got a compliment at the gas station.

BAD-HABIT

Well lets see...I would guess you should be running between 48-55 W.O.T depending on type of prop and engine condition. Is the prop stainless? 3 or 4 blade?Also get a GPS to judge your speed forget the speedo. You mentioned no fluid in the tilt/trim motor. If you have an aluminum prop and had the drive all the way in/down and a full load on board 35mph or so might be right...Especially if the speedo is off. Before I changed speedo's the stock one always read slow. At 40mph it probally read 35 or so.....So again whats your prop, and did you trim the drive up for maximum speed?


BH

bowtie89

Its a 3 blade stainless steel prop!!! Not sure of the pitch and I did was put the drive all the way down. The engine runs great it fires up great first crank!!! I just dont know I hope 35 is wrong I as told the boat did 55

BAD-HABIT

Well again get/borrow a GPS...You can get a handheld one for about $89. Also if you had a full load(gas,people etc) and had the drive down you probally were doing 35-40. YOU NEED TO TRIM THE DRIVE UP! Maybe I am misunderstanding you on this. Do you know how to trim the drive for maximum speed and efficiency....Also does your prop have any dings?

BH

Iggy

Check the prop for the part number, it will be stammped on it. Tell us what it is and we'll tell you what the prop really is.
I have a 21" pitch Mirage prop. P/N stamped on mine is 13702-A40-21P. Merc no longer makes this prop. It was replaced by the Mirage Plus. Formula claims I have the wrong prop. Their records show that the Laser II at 19" pitch is the right one to use.

Top end sould be 58 mph @ 4800. Mine does that (GPS verified) with over 400 hours on the engine. And even the Formula brochure from the era claimed a top end of 58 with the 21" prop. 56 with the 19" pitch.
Don't believe the speedometer. Mine always reads low, but not that low.

If you have time check the tube running up from the transom mounted pitot (little white plastic piece to the right of the outdrive), through the hull and up to the gauge. Look for cracks, loose connections, etc. Mine had rotted at the transom and a section had to be replaced.

bowtie89

I will check the prop info when I get home tonight. I don't know how to trim the outdrive for max speed. I didn't know you could do that. Where can I go to get a handheld gps?? It was only me and my father on the boat half tank of gas. Iggy what rpm does your boat fall off plane?? Also what diameter is your 21pitch prop?? Is it 14 3/4???

Scott72

I had a 21" Laser II on my old Four Winns Liberator with a 350 Mag. It topped out at 54-55 on GPS at around 4800 running light. Cruised at around 38-40 at 3500 if I remember correctly (been a while). Great motor, couldn't kill it. Even after 400 hours it didn't really burn oil. Boat did like to be trimmed up. Don't rely on the speedo, mine wasn't even close and bounced all over the place.

Iggy

I believe the prop diameter is the same, 14 3/4".
I think it falls off plane around 2600 rpm. Next time I'm out I'll check and report back.
Formula engineers said best economical cruise is at 3500 rpm.
Best place to find a GPS? Check marine supply stores, sporting goods and online. I have a Garmin GPS. Don't ask what model it is, they don't make it any more. They're the best thing to have. Especially if you'll be out on Long Island Sound. The fog gets real thick out there. I know.

How you trim for speed is you bring engine up to full throttle, trim the drive up a little at a time till you hear the engine rev like it's slipping (it is), then trim it back down till the prop grabs again and it's at max RPM no higher. If your trim gage is working right make note of the indicated position for later reference. Also be sure to bring the tabs up too.

bowtie89

Iggy I sent you a pm

Iggy

Got it.