Pontoon Boat & Deck Boat Forum

I recently purchased a 2015 Crest Continental with a 350 Verado. When I purchased the boat, the motor was mounted at the lowest setting. I've since raised the motor two holes and got a little better speed and handling but it still seems slow to me. The cavitation plate is sitting an inch or so under water at cruise or WOT. I wanted to get opinions before I raised the motor any further. My goal is to be more efficient at cruising speeds as it seems like I should be going faster than 27mph @4500rpm's.

2015 Crest Continental
About 5k lbs fully loaded
350 Verado 20" shaft with 1.75 ratio
14.5 x 16 pitch Enertia Prop
Engine Mounted 3rd hole from the top
Cruise at 27mph @4500rpm's
WOT is 49mph @6400rpm's

Weight.
Wait....weight?
WEIGHT.

Heavy azz boat and drag. There's a speed chart of the same boat at the link below with a 250 and their results indicate you're probably about where it's just going to be. Compare your two speed points and it looks about right....compared to that boat tested, a 100hp increase on a 5000lb toon is only going to gain a few mph. Also although you've still got a good lb/hp ratio, with a boat there's more to it since more weight equals more displacement and drag so you don't get a directly proportional increase in performance. For instance, my boat has a worse lb/hp ratio than yours but does 27mph at a little lower engine speed....I'm sure because of having less drag.
https://www.pdbmagazine.com/2015/05/cre ... ontinental

For comparison...although not apples to apples....here's a Yamaha 250 and 300 tested on two boats that are very similar to one another.
250 https://yamahaoutboards.com/en-us/home/ ... -08-20_pnt
300 https://yamahaoutboards.com/en-us/home/ ... -07-13_pnt

Also if you're talking about efficiency, the most efficient cruise speed is typically 3500RPM or below. I'm not sure about on the supercharged models. Now, we all know that our real "efficient" cruise speed is really the speed that feels good to us without thinking about gas.

double post, deleted

Does it have lifting strakes?

Thanks for the input Steiner, while I do agree that it is a heavy boat I can't help but feel like I'm missing something. The reason is because I've been researching this motor and came across all these pdf files for tests Mercury did for different boat/motor combinations. In the section 175-400 Outboards, there's a test for a 27 foot Tahoe with my exact motor and prop. The results looks pretty similar to what I'm getting (the Tahoe seemed to run slightly better), but the Tahoe weighs in at 5k lbs dry and 6.2k lbs as tested.

The Tahoe is getting 28.9 mph@ 4500RPMS and 51 mph @ 6450 rpms.

My estimated boat weight is based on the boat(4klbs), engine (670lbs), me (200lbs), and basic gear (10 life jackets, two small anchors, boat table, boat canvas, 25-35 gallons of fuel). So I'm about 1,000 lbs lighter than the Tahoe and getting slightly worse results.

Another thing that makes me think somethings off is that I seem to really lose mph with any type of load or going into the wind. I was driving with another person going into the wind (10-12 mph) and at WOT I was only hitting 42 mph.

I think I did mention that I raised the engine from the lowest setting to the middle setting. I did this primarily because the boat almost felt like it was porpoising when I hit any waves. Before I raised it, I was only getting about 25mph @4500 rpms. The boat rides much better after raising it but I can't help but think I may need to raise it to the highest setting. My cav. plate is still under water in the middle setting @ cruise speed but only by an inch or so.

wwind3 wrote: ↑

Thu Jul 30, 2020 4:29 am

Does it have lifting strakes?

Hi wwind3, I have strakes on the center tube and insides of the outer tubes.

Yeah, I saw that same Mercury file. Not sure how much it affects it, but the Tahoe has 27" tubes compared to....I think yours is 25"? Also they have strakes on both sides of all three which is supposed to be for best efficiency/speed whereas I think your setup favors agility.

How much does trim affect it?

Steiner wrote: ↑

Thu Jul 30, 2020 6:06 am

Yeah, I saw that same Mercury file. Not sure how much it affects it, but the Tahoe has 27" tubes compared to....I think yours is 25"? Also they have strakes on both sides of all three which is supposed to be for best efficiency/speed whereas I think your setup favors agility.

How much does trim affect it?

Yeah, mine has 25" outside tubes and a 26" inside tube. Trim doesn't change too much except when I'm all the way down, I lose about 2-3mph. I can trim it up about 80-90% before I start to get blowout but it doesn't really affect speed. I tend to cruise at about 15-20% trim because at higher trim I don't sit down on waves as nice and the speed doesn't change from there until the 80-90% mark. I calculated, and at wot I'm at about 13% slip which isn't bad but I spend most of my time in the 25-30mph range where my slippage is considerably higher (around 31%). I'm wondering if I switched to a larger prop or a 4 blade that would make a difference at mid-range bite.

Imo, get your cavitation plate at or above water. Plus from my experience the enertia prop can handle high outboard mounting positions.

Just to update, I raised my outboard from the middle hole to the bottom hole. I dropped to about 42-4300 rpm's to be at about 27-28 mph. I can just see my cav. plate at cruising speed.

I also did the Mercury prop selector and it recommended I have either a Rev4 in the same size and pitch I have now (14.7d, 16p Enertia) or the Enertia Eco in a 16 diameter at 17 pitch.

I have read good things about the enertia Eco. The question is whether your outboard can spin it as 17 is lowest pitch I think. Did you gain rpm at wot when you raised outboard? WOT speed with new position?