cruiser efficiency

[PT Man]

First thanks for the quick response I received on last post Now I will be more specific Some people have told me the hull was designed for a staight inboard,But Bayliner mounted a very heavy 460 with outdrive.Now to complicate this there is a 50 gal water tank a 10 gal water heater & 2 batteries all in the engine compartment. I was wondering if moving the water tanks to the bow or midships might help.I would appreciate any thoughts on this matter

[mmd]

At the risk of being facetious, do a trial to check if moving the tanks will be benefitial. Empty the water tank & heater and place an equivalent weight (500 lbs) of sandbags on the cabin sole or in the bilge where you think you can relocate the tanks to, and take the boat for a spin to see if the performance improves.

[Willallison]

Remember also that any improvements will only be there so long as the tanks are full.....

[PT Man]

Hi Guys
I actually did do some experimenting this weekend anyother suggestions welcome
Thanks

[mmd]

Well, PT, don't keep us in suspense! What experimenting did you do, and what were the results? Inquiring minds want to know ....

[PT Man]

Hi All
Drained as much water as is possible Put coolers and loose gear in bow gained about 1 mph still no plane
Thanks

gained about 1 mph still no plane

What do you mean no plane? With all that power your boat isn't getting on plane at all??? Or is it that you want it get on plane at a slower speed than it currently takes 25 or 30 mph to get up and thus you don't have the 15-20 mph speed range available (you have to gun it to go from displacement to planing)?

[Willallison]

I run a Searay 270 sundancer with a 260hp Mercruiser. It tops out at around 35mph and I can hold plane (with tabs and drive trimmed right down) to around 15 knots (very inefficiently). My boat has an 8'6" beam, whereas your bayliner is somewhat wider I believe, so probably a bit heavier, but given that you run a bigger engine, you should probablyt be able to expect similar performance.
I've just gone back over your 1st post about this problem. You said that the boat runs a 7.5L Volvo sterndrive...what is the horsepower rating of the motor?
Assuming it is 300hp+, I can't help but go back to revisit a suggestion I made to you earlier. You said that the prop is in good condition and that the bottom is clean - but what is the pitch of the prop? Running flat-out what revs are you pulling - and is that the maximum rated revs for your engine? If you are not getting full revs, then chances are the boat is over-propped - try a lower pitch - a 17 or even 15" inch pitch.
I'm not sure whether Volvo use a flexible spline in the prop centre as Mercury do, but if so and your motor is revving wildy but just going nowhere, then perhaps the centre of the prop is 'blown out' - try a new one.
Big companies like the Brunswick Corporation (who own both Bayliner & Searay amongst others) simply can't afford to build boats that are complete dogs (granted some earlier Bayliners weren't exactly standout boats, but anything produced in the last 10 - 15 yrs should be fine)....I'd be very surprised if there isn't a simple answer to your boats performance woes....

[PT Man]

Hi
I am hoping for a simple or even rediculus answer but My problems usually tur out to be unreal. the drive is a king cobra,running 15x17 @4200 rpms 13 mph I know it sounds crazy but my problems ussually are
Thanks
Mike

[mitch]

From what you wrote ,it sounds like the rubber hub in the prop is shot.Take it to a prop shop to have knew hub installed. The 7.4 ltr (454) is rated at 310 hp. My cruising rpm is about 3500.

[Willallison]

I'm with Mitch.

A # of years ago my father bought the same boat. while it was very sluggish getting on plane, it performed well once on top, Much to my surprise. A confortable cruise speed was between 3200 and 3500.
I agree with the earlier comments of the big block needed to move the displacement, the added weight however doesn't help. High RPM and no plane certainly suggests slippage at the prop. Once you determine if that is the problem you might want to find a good Prop shop that may let you try different props, prefferably stainless it flexes less under your heavy load. The right prop can make a world of difference and put fun back to your boating.
One last thing for somewhere between $50 & $100 you can buy a planeing fin that attaches to your outdrive ( Dolfin ). Good results for cheap money

Good Luck
Tim

[Willallison]

The addition of "Dolphin" type fins to the cavitation plate can have dramatic effects on performance.
I used to do a lot of competition waterskiing. One of the o/b boats I drove was retrofitted with a set and it completely transformed the boats handing. Others have experienced varying degrees of success using them.
I have a set fitted to the Bravo 11 leg on my boat and it certainly has improved low to mid speed planing ability. But be aware - I know of a number of instances where fins have caused a failure of the cavitation plate - ie it has broken due to the added stresses placed on it. I'd be hesitant about fitting fins to a boat which is likely to be doing much high speed work in rough water.

As far as the addition of a stainless prop goes, this isn't such a good idea on boats being left in the water. With your sterndrive (or o/b if it won't trim completely out) made of aluminium and the prop of stainless, you create a perfect situation for electrolysis to work - and it will be the leg which becomes the sacrificial half. True there are performance benefits to be had by going stainless, but I don't believe they're worth the risk on a permanently submerged drive.

Hello,

I have a 2550 Bayliner Sierra Sunbridge. I have had similar problems with propellors. Best bet is to buy a new propellor. Rehubbing an original Volvo prop is a real problem. Volvo uses an epoxy like JB weld to keep the rubber grommet in the hub. People who re-hub these props will offer no guarantee on these props, and even complain forever about these props. Buy a replacement Michigan propellor. I would try a 17x15. Find out what the most common propellor is. I forget whether I use a 15x17 or 17x15. The most common one should fix your problem.

I get 26mph with a 26' boat and chevy 350. You should be able to hear the engine let loose when the prop starts spinning in the hub. I wish I could get 30 in a bad way. I am at 3300 rpm. I think your big block should be used at a lower RPM than the 4200 you were speaking of.

[Willallison]

I get 26mph with a 26' boat and chevy 350

Surely that's not running flat out...?
With my similarly powered (mercruiser 260) 27' Searay I used to cruise @ 20 - 22 mph (depending on load) @ 3400 rpm. Flat out was around 34 mph