Speed sound right?

[pmat1]

I have a 1986 thundercraft regency (i beleive) 16 ft, not sure of actual weight but its not extremely heavy. with a 1985 evinrude 70 e70elco with 135 compression on all 3 cyl. i max out at 26 mph with a 15 pitch prop. does this sound about right? anything i could do to help? being a teenager i love speed

 

[Boss Hawg]

Re: Speed sound right?

I have a 1986 thundercraft regency (i beleive) 16 ft, not sure of actual weight but its not extremely heavy. with a 1985 evinrude 70 e70elco with 135 compression on all 3 cyl. i max out at 26 mph with a 15 pitch prop. does this sound about right? anything i could do to help? being a teenager i love speed

Not farmiliar with your boat but i have a 1987 16' fiberglass bassboat V hull with a 1987 70hp Johnson (19 pitch prop) that will do 40 @ 5500rpms on a good day

 

[countvlad]

Re: Speed sound right?

I have a 1986 thundercraft regency (i beleive) 16 ft, not sure of actual weight but its not extremely heavy. with a 1985 evinrude 70 e70elco with 135 compression on all 3 cyl. i max out at 26 mph with a 15 pitch prop. does this sound about right? anything i could do to help? being a teenager i love speed

whats your RPM at WOT?

 

[ezmobee]

Re: Speed sound right?

Unless your boat is waterlogged I would think you'd be able to hit 30-35MPH.

 

[pmat1]

Re: Speed sound right?

whats your RPM at WOT?

Back when i had a tach it was 6500. The tach froze up on a rough day.

And it actually was waterlogged once. it did about 10 and would not plane at wot.

 

[pmat1]

Re: Speed sound right?

Here is a pic if it helps anything..

 

[ezmobee]

Re: Speed sound right?

That WOT RPM is way high. Your looking at around 5500 (I believe). And I didn't mean waterlogged as in has a puddle of water in it....I meant perhaps you have water saturated floatation foam or rotted wood making your boat heavier than it should be.

 

[ezmobee]

Re: Speed sound right?

Nice looking boat. Where are you in PA?

 

[pmat1]

Re: Speed sound right?

That WOT RPM is way high. Your looking at around 5500 (I believe). And I didn't mean waterlogged as in has a puddle of water in it....I meant perhaps you have water saturated floatation foam or rotted wood making your boat heavier than it should be.

oh no last month it was not getting on plane so i cut a hole in the deck and it was FILLED with water. took about 40 min to pump with a 500gph pump. it is bone dry under the deck and there is no foam

and it actually looks better now thanks to vasaline
i am about 30 min northwest of Reading.

And there is basically 3 speeds on this boat. idle, plow, and plane. WOT is plane. anything lower is plowing.

 

[crb478]

Re: Speed sound right?

What size motor is your boat rated for? The motor on it looks kind of small to me, but I could be wrong about that. How was the water trapped under the deck? Are you sure that the stringers are sound and not waterlogged. The boat looks good but it does look like it could handle a 120 or 140 hp motor. If that is so then you are probably underpowered.

 

[pmat1]

Re: Speed sound right?

Its rated for a 115. the stringers and deck are not in the best of shape, but they will last until the end of the season. the weird thing is ive been passed by 16 ft trihulls with 50's on em. kinda sad really

 

[jdsgrog]

Re: Speed sound right?

Not sure if you posted on youtube, but I found a thundercraft regency (an '87 16' 2") having trouble getting on plane.

Anyway, back to your concern; if you had gotten 6500 rpm, then you may not be propped right. your motor may be able to handle a higher pitch which will in turn increase speed (theoretically). You are running a motor with about 60 percent of the rated hp. 26mph may be all you get with that motor and that pitch propeller. If your boat can handle more pitch, I'd go up a few inches in pitch to a 18" or even 19" pitch prop (unless you are doing a lot of water sports). I would think that would increase your top speed to nearly or slightly above 30mph and keep your motor in the proper rpm range. With a true v-hull boat, I would also consider getting some sort of tabs to get on plane with lower speeds. A v-hull by design generally needs more power/speed to plane than a trihull or any flat bottom or modified/semi v-hull. If you're looking to get blazing speed (50's to 70's) I doubt that boat was made for that and you will likely have to overpower significantly and risk damage, safety, etc. In these forums, it's usually not recommended to over power. If you're looking at mid/upper thirties or even low forties, you may need a new motor closer to the hp rating with a properly pitched propeller.

 

[pmat1]

Re: Speed sound right?

Its not like i want to have a speed boat or anything, i just want to get as much from the motor thats on it as i possibly can. i will most likely be ordering a 17 pitch prop, do you think i should go 4 blade?
and i would not trust that boat with a 90 or higher

Also, i do have a Doal fin for it that i took off because it lowered my top end speed and i heard it was bad for the transom/motor mount?

 

[Rancherlee]

Re: Speed sound right?

I agree that is should be running at least mid 30's for speed. There IS foam somewhere on that boat, unless the floor has been redone in the past and someone removed it all, and it probibly IS waterlogged. Also, you should run at the very least a 3 blade 17 pitch prop and possibly a 19 pitch. On my heavy aluminum 16' foot, riveted hull, semi-vee Lund With the same motor you have I was running 35mph with a 17 pitch prop and over 6000rpm with water logged foam. I redid the floor and foam and LOST 300# of dead wieght and brought my speed up to 37mph and had to go to a 19 pitch to bring the speed rpms down to the 5500 range. When I got my 70 4stroke I gave the 70 2 stroke to my buddy to use on his 21' Starcraft CC fiberglass boat and it managed to get his on plane and run ~30mph with a 15 pitch prop. His boat is rated for 140 and he still has not gotten around to getting his 120 fixed can continues to run my old 70 to this day.