New Owner

[PartyBarge]

Greetings, first post. We are the new owners of a 2004 Bennington 2080RL with an F90 Yamaha. Surprised to realize this pontoon was built less than 10 miles north of where I was born and raised.

This unit is in nearly new condition, the efforts of the previous owner show well. The excellent build quality shows too. I only found one loose bolt under the deck, also the helm area light was never connected. I reattached the nitrogen strut for the gas tank cover with larger screws as the originals had pulled out (at least twice).The structure is much tighter and stronger than our previous 1993 JC SunToon 20 with a Johnson 70hp 2-cycle.

That said, it appears the previous owner attempted to address some issues (unsuccessfully, in my opinion). For our test drive, the motor was mounted in the full down position (motor bracket sitting on the transom, although it appeared the motor had been one hole higher at some time) and had a Doel Fin. The prop was a 13 5/8 x 13p! As you might imagine, the RPM went right to the rev limit and the top speed was only 20.5 mph maximum for a light load on the Garmin 535s GPS. The bow would ride very high at any and all trim settings. Scored some points when I told my wife that she just wasn't heavy enough to hold the front down...

After she decided we should upgrade, I set about correcting what I considered a mis-rigged boat. First, we junked the whale tail. Next the dealer let me try a couple props, a 13 3/4 x 15p was, oddly, way too much as RPM did not exceed 4900. A 13 5/8 x 14p produced, an expected, 5700 RPM and topend was unchanged. So, I went with that for now. Had no idea why the 15p dropped the RPM so much as it appeared to be a generic aluminum prop just like the others...but I think I know why now. 

Changed the spark plugs to Autolite double platinums just to be sure (the old NGK's looked just fine). Next, I raised the motor from full down to full up (that's a change of 2 1/4") on the existing mount bolts. We now get 23+ GPS @ ~5900-6200 RPM (the tach is a little flaky...will exercise the selector switch/connections soon).There is no sign of the prop unhooking. Even yet the only time trimming up will increase speed is above 4500 RPM. It does seem that this model pontoon would be happier with about 100 pounds less hanging on the transom...as in a 90hp 2-cycle vs the 90 4-cycle.

Anyway, if I can drum up the time/ambition, I'll drill new engine mounting holes. The most available is another 1 1/2" up. so that is the plan to see what happens. Also, maybe the dealer will let me try a different 15p prop (although the same one may work when the engine geometry is optimized)...Or, does anyone have the perfect prop suggestion for this pontoon/motor combination? A SpiteFire of 13 or 15 pitch sounds appealing at the moment.... This combo should have another couple MPH hiding somewhere if the geometry and prop are right....even with the 23" logs. Cheers and thanks for replies.

 

[Bamaman]

Welcome to the forum. 

You wouldn't, by chance, have a 25" motor would you?  With 20" motors, they're usually mounted all the way down, or 3/4 " up (1st notch.)  Sounds as if your motor was plowing after being too low in the water.  The doel fin usually lifts the rear a little, and doesn't hurt speeds.  Glad you're seeing some improvement, however.

2 toon boats are displacement hulls, and trim doesn't do that much to get the nosecones out of the water.  I always ran my motor on my twin pontoon boat parallel to the bottom. 

23 mph is about all you'll get out of a 90 hp toon.  If you're not getting any prop ventilation, that's about your optimum level.  You can throw all the propellers you can at it, but you'll quickly hit the point of no return where it's all wasted money and effort.

 

[cwag911]

Welcome to the family and I second what Bamaman said. You're probably at your limits.

 

[SEMPERFI8387]

What they said ^^^^^^^^^ and PICS !!!!!!!

Oh yeah, welcome to the family !!!!!

 

[lakeliving]

Congrats on the boat. Welcome to the Bennington obsession!

 

[1Tiredlady]

Welcome to the club; looks like a pretty boat. Where are you located?

 

[Ben & Suzy]

Bamaman X 3.

It does sound like you have a 25" mid on a 20" transom. If so, a manual jack plate with 4" or less of setback would be the remedy if it were mine.

 

[PartyBarge]

Thanks for all the replies!


I solved the flaky tach, the center connector was loose. Solid indications now.


According the Yamaha website, our F90TLRC, serial 61PL1006XXX, is a 2004 saltwater approved 20" motor. The tag on ours indicates it was actually built in Dec '03.


Since my last post, there was opportunity and inspiration to drill new transom holes at the maximum up position and lift the motor another 1 1/2" (now for a total of 3 3/4" from motor sitting on the transom).


Speeds @ 2000, 3000 and 4000 Rpm are up several tenths MPH to about 1 MPH @ 4000...all with trim full down (that actually is a couple degrees of tuck-under on this pontoon). Any up trim at less than about 4500-5000 RPM costs a few tents MPH. AT WOT, RPM is 6050 to 6100 and there is speed gain with trim up to about 1/2 the gauge scale (I don't remember what the speed was @ full down). Above that trim position, speed decreases about 1 MPH, but the prop does not unload until reaching nearly full scale up (not sure where that is for actual motor tilt). Now for the best part. A two way average of max speed was 25.7 (I saw a temporary max of 26, light chop may have effected that)! This was with just me and 3/4 tank of fuel. BTW: All data listed in my posts is from a Garmin 535s GPS and with the parachute...I mean 10-foot Bimini deployed. The shape of that thing looks to be generating some lift...will have to be careful running into the wind....hehe. Anyway, I'm now a happy 'tooner! It appears the speed increase is due to reduced drag (and, thus, some reduced prop slippage too). Drag was directly reduced by lifting the motor, but I'm confident interference drag between the pontoons, as well as the engine canoe, is significantly less as the deck angle is now way better for speed.


I won't try any more motor lift until there is some data with a load of at least five adults...and any more would require structural modification that I likely won't do anyway. In fact, I won't be pursuing the optimal prop until there is more testing either...might already have the best prop...unless, of course, I stumble into a pontoon specific prop, like a Spitfire, of a 14 or 15 pitch.


From various comments, I'm pretty sure my results (and need for the adjustments) are specific to our pontoon/motor combination. And, I have seen some pontoons provide a way to adjust the engine mounting canoe that effectively changes motor height without moving the motor off the transom. My results (with the 5 MPH speed gain) put this unit pretty well inline with similar pontoons (except for the motor mounting) in the Yamaha Performance Bulletins. That said, if you have a 2080RL (23" tubes), or similar, you may want to re-examine the motor mounting.... I have no idea how much extra gas was burned in the previous condition over the last nine years...


Although I learned to ski in the early to mid '60's just south of the Bennington plant on the St. Joe river, we now live in NW SC on Lake Keowee. If I figure out how, I'll post pics of what I like to do most on the lake...hint, it ain't pontooning... You might say we are a multi-threat family, kayaks, power boat (Stingray), wave rider and pontoon. However on the big weekend afternoons, we mostly ride the upper deck of the dock and watch the circus!

 

[Ben & Suzy]

Ha, I just noticed your pic.  You have the same Super Sport color combo as our 04' 2050 RL.    

 

[PartyBarge]

Well after additional tests and a visit to the marina dealer, we decided to try a generic aluminum 15p prop. This one is a rebuilt 13 1/2x15p with a pressed-in hub (the previous try with a new 15p used a hub insert). No telling exactly how the rebuilt prop compares to a new one. However, the results were a pleasant surprise! The two-way top end was the same 25.7mph (as with the 13 5/8x14p), but max RPM is now 5800 (versus the 6150 before). Now the best part, mid-range acceleration is BETTER! With the 14p, the motor would quickly wind near max RPM and the pontoon would speed up as slippage/drag decreases. The rebuilt gets to some 5000+ rapidly and then RPM builds just a bit faster than actual; speed. Calculated slippage @ max RPM/speed is ~27%. That's great for a generic on a pontoon (until I can reduce drag more).

I was about to get a pontoon specific prop of 12 or 13p (as they run slippage in the low teens, or better). But that is on hold indefinitely. Instead, adding a wave shield as others have done is a serious consideration. Our previous JC Sun Toon had one that covered the tube risers  along with strakes on the engine pod. Didn't realize how nice those are! Sure wouldn't hurt in the "reducing drag" department either....