Boston Whaler Conquest 280 planing

[AlfredoS]

I read in an earlier forum of a problem in the same boat with 225 4stroke yamahas. I just changed engines to 250 hp 4 stroke and experiencing planing problems. When the boat is fully loaded is very difficult to plane.... Sometimes even imposible. Original engines mercury 225 optimax where better, altough it was always tough to plane when fully loaded. Has anybody had the same problem? or better, a solution to the problem, It?s been really frustating spending a lot of $$ and still having this sort of trouble.
I remain awaiting anyone kind reply.
Regards

 

[DJ]

Re: Boston Whaler Conquest 280 planing

I read in an earlier forum of a problem in the same boat with 225 4stroke yamahas. I just changed engines to 250 hp 4 stroke and experiencing planing problems. When the boat is fully loaded is very difficult to plane.... Sometimes even imposible. Original engines mercury 225 optimax where better, altough it was always tough to plane when fully loaded. Has anybody had the same problem? or better, a solution to the problem, It?s been really frustating spending a lot of $$ and still having this sort of trouble.
I remain awaiting anyone kind reply.
Regards

Very difficult questions, without data. I read your post in the "other" forum.


1. How many RPM's at Wide Open?

2. Is the bottom CLEAN!?

3. What prop's.?

 

[walleyehed]

Re: Boston Whaler Conquest 280 planing

I'm very interested in the answer to DJ's questions especially #1 and #3...I would "assume" if they pulled the boat for re-power, the bottom got scrubbed if needed..???

 

[AlfredoS]

Re: Boston Whaler Conquest 280 planing

Thanks DJ for your prompt reply!
Regarding your questions,
NO. 1 the max RPM about 5900-6000 when properly trimmed probably 6000 at 35-36 knots
NO. 2 The bottom is clean is white painted and the boat is kept out of the water, even polished.
NO. 3 I?m going to check and post you later
I will also get the distance from bottom of the hull to the cavitation plate in the engine.

 

[steelespike]

Re: Boston Whaler Conquest 280 planing

Just as a reference Twin Etec 250s (not HO)on a Proline 29 grand sport 6300lbs. dry 14.75 X 19 stainless max rpm 5,750 @ 52 mph 4 sec to plane. Proline 32 WA 9,900lbs dry 14.75 X 17 stainless max rpm 5,900 @ 45 mph 8 sec to plane. Capelli 32WA 6,600 lbs dry 14.75 X 19 stainless 5,700 rpm @ 50 mph. 5 sec to plane. these average about 43gph @ wot.
It would seem your motors should be competitive on your boat.
As I understand it 4 strokes require careful propping and setup.
If your dealer can't get it done I think I would twist his and Yamahas tail a little.

 

[AlfredoS]

Re: Boston Whaler Conquest 280 planing

Do you think trying a Mercury Revolution 4 14 5/8" x 17" prop would make any diference?

 

[steelespike]

Re: Boston Whaler Conquest 280 planing

I'm not a prop pro but generally a 4 blade performs better at the low end;
but you'll probably lose some top end.
Difficult to know how it would do without knowing your present prop application.

 

[AlfredoS]

Re: Boston Whaler Conquest 280 planing

the actual props are yamaha standard, the M19 they have: 14 1/2"x 19"

 

[steelespike]

Re: Boston Whaler Conquest 280 planing

Again not a pro and I don't know what your gear ratios are but it appears to me that at 6,000 rpm you should be closer to the Etecs speed unless the Whaler hull is really slow/heavy.Twin Etecs are running almost 46 @ 5,900 on a 10,000 lb Proline.with a 14.75 X 17. Is your speed by gps?Is the tach accurate?Maybe someone here can come up with the approximate speed for your setup.

 

[Frank Acampora]

Re: Boston Whaler Conquest 280 planing

From what I understand, 4 cycle engines (because they have only 1/2 the power pulses per revolution) don't have the same "oomph" as an equivalent 2 cycle engine. That's why Mercury went to supercharged Verado engines--to improve the lower end response--and lower end muscle is what gets you on plane. Doesn't matter if the horsepower is the same, it matters where the horsepower is developed in the power band.

Of course, if you don't have them, Trim Tabs will help to get onto plane.

If you don't have tabs, for a couple hundred, might be worth experimenting and investing in Smart Tabs. I have no experience with them but a lot of the guys on this forum swear by them.

 

[AlfredoS]

Re: Boston Whaler Conquest 280 planing

I have trim tabs, the boat eventually planes but there are situations that make this marginal power very difficult to handle, specially in high seas where you need to go slow but planing. What happens is that you end up spending a lot of gas as your motors are max?d and the rpm?s barely at 3,500-4,000.
Has someone has expierence with the 4 blade propellers? they say they help in a problem where the stump is missing, The venting system some people say they help getting the engine to accelerate.

 

[jay_merrill]

Re: Boston Whaler Conquest 280 planing

Five hundred horsepower on this boat should not be marginal horsepower. While it is rated for up to 600 hp, the lowest recommended power is 300 hp. I just surfed a bunch of ads for 28' Conquests for sale and most seem to have the 225 Optimax engines. I saw WOT speeds at about 38 mph for most.

If you are at 5900 - 6000 rpm at WOT, you are right where you should be in terms of prop pitch. I have no experience with 4 stroke Yammys, but once again did some surfing. Apparently the peak torque powerband is in the 2000 - 3500 rpm range for the 250hp model.

For the boat to fight planing that much with both engines running makes me curious as to how you load it. Is there anything unusual about how you run the boat in terms of overall weight or fore/aft weight distribution? If not, something seems to be very abnormal and I guess I would be talking to both Boston Whaler and Yamaha to see what they think.

From what I have read concerning 4-blade props v. 3-blade, the 4-blades will get you up on plane faster and are in their optimum performance "envelope" at midrange speeds. They are not the prop of choice if top speed is the goal but that doesn't seem to be an issue here.