Should I put a 200hp on my boat?

[sasqman]

This is kind of a continuation of my "prop question" thread.

Me and my wife both love our boat. Its got a great layout, not the flashiest lines on a boat, but good for fishing and keeps out family of 5 comfortable while on day trip cruises. So part of our decision to keep this boat will depend on the performance of a repower. We are not speed junkies, but it would be nice when the condition are optimal to get across the straight a little quicker than our current 2 hour journey. Currently I have a 2005 mercury 115hp with the 11p prop and get a cruise speed of 8 knots at 4200 rpm, and top speed of 12-14 at 5500 to 6000. My question is, what would 200hp give me a far as performance goes for a cruise speed and a top speed.

Here is an article about my boat that should answer some questions. The roll on mine isn't as bad as the stock, as I do have a 300 liter gas tank about 3 feet forward of the stern and sits about 1 foot below the water line and have a 200 liter fresh water tank in the bow that sits about the same below the water line. The extra ballast helps when full.

https://www.canadianyachting.ca/boat-reviews/72-power/3077-bayliner-2650-explorer

Ask any questions. I know there are some really smart people on here and I would love to pick their brains and gain some education on this before I talk to a dealer, or decide to get a different boat.

Thanks all!

 

[Canso]

I think you need a 250Hp and you will wonder why you didn’t do it sooner. Great boat BTW, you will love more power.

 

[Stosh]

If your boat has a displacement hull, it has a maximum hull speed. Increasing to 200 hp won’t make it go past the hull speed.
Stosh

 

[zurk]

2 x merc 450Rs for some real kick.
no seriously just leave it alone.

 

[kaelc]

I’ve always been interested in that model of bayliner! I would guess a 150hp would be max to safely use but check the hull rating it should be on a card mounted on the inside of the hull near the helm?

There is a great bayliner forum where someone will have tried to put a bigger engine on as well but sounds like a good package. I have a 26 c-dory which performs quite well with 150hp but it is designed for going 30kn. I would listen to Tosh’s advice. Happy family boating!

 

[Foxsea]

Hulls are designed to match a speed potential. Whether an engine suitable of meeting that potential is provided is a secondary consideration, and one hopefully to be made by a reputable builder and an informed owner. Also, remember the dominant factor that weight plays in determining whether or not the boat can achieve the speed goals you have set.

No one boat does a broad range of speeds well. A hull designed to go fast likely will be uncomfortable and inefficient at lower speeds. One designed to go slowly usually is terrible if pressed beyond its optimum. In that sense, a hull designed for the middle-speed range may be the right choice if those speeds best fit your needs. In choosing a boat, be sure you understand the compromises so the decision is an informed one.

Colin Mudie, designer, philosopher and author of the 1977 publication Power Yachts, expressed these thoughts with the dryness that only an Englishman would bring to the topic. He referred to the semi-displacement range as: "an unfortunate region full of hazards and disappointments for boat owners." In defending his placement of the topic within his book, he added: "We will include them with the displacement group as it seems more polite to consider them as rather overpowered-displacement vessels than as planing boats which could not quite make it." Adding more power to a semi-displacement hull ignores the reality that the hull is the speed limiting factor.

 

[Fisherman Rob]

The article describes it as a semi-displacement hull. I suspect that more power might get you to 8 knots cruise (hull speed) with less rpm. Past hull speed and up on the plane, you might add an extra couple of knots to your current top speed of 12-14 at max RPM, but your fuel burn will likely be much higher.

 

[bigbruce]

With that hull, I’d look at going to a13 or 15 p prop before doing anything else. Should give you a bit more speed at lower rpm. Going to be tough to get it on plane no matter how much hp you throw at it.

 

[sasqman]

Thanks for all the input guys. This is a big decision on repowering or reboating.

So here is a video of the wake I have at WOT 5500 to 6000 rpms with my current set up. This is doing about 13 knots. Does that wake not seem like it's planing? I feel a difference when the boat is pushing hard at 9 or 10 knots compared to this. Thoughts.

 

[Foxsea]

Planing is possible on some boats at 13 or 14 knots but again, hull length, design and weight are limiting factors. With the tankage and passenger load on your boat and considering the shorter, semi-displacement hull design, adding double the power will certainly not come even close to doubling your speed. But the operational costs could easily triple. A semi-displacement hull will still be pushing water rather than gliding on its surface. The physics on this are well understood. If you want speed in a smaller boat, buy a planing hull.

 

[sasqman]

Planing is possible on some boats at 13 or 14 knots but again, hull length, design and weight are limiting factors. With the tankage and passenger load on your boat and considering the shorter, semi-displacement hull design, adding double the power will certainly not come even close to doubling your speed. But the operational costs could easily triple. A semi-displacement hull will still be pushing water rather than gliding on its surface. The physics on this are well understood. If you want speed in a smaller boat, buy a planing hull.

Thanks for the insight Foxsea. The more research I do and more input I get like this, it is making our decision easier. I love the idea of it, but a lot of money to spend with out the desired results.

In the meantime I have ordered a 12p x 14" and will try in next week when it arrives. See what she can do.


Thanks again

 

[Pineapple Express]

Planing is possible on some boats at 13 or 14 knots but again, hull length, design and weight are limiting factors. With the tankage and passenger load on your boat and considering the shorter, semi-displacement hull design, adding double the power will certainly not come even close to doubling your speed. But the operational costs could easily triple. A semi-displacement hull will still be pushing water rather than gliding on its surface. The physics on this are well understood. If you want speed in a smaller boat, buy a planing hull.

Agreed with @Foxsea here. You might go a few knots faster with 200hp but it won't be the dramatic change you're looking for.

The sunset video you posted does look like you're technically planing to me but it's hard to tell for sure since you don't show the water flow at the transom. Planing is defined by when the boat is supported by hydrodynamic forces on the hull supporting the boat, rather than buoyancy. The rough approximation to determine when you begin planing is when you observe the water separating cleanly from the aft edge of the hull and the transom is not immersed in water (ie you could have an open hole in the transom and it would be dry). Still, at these low planing speeds you're still pushing a lot of water around and more power would push more water without a tremendous increase in boat speed.

If you put enough power on the hull to really get moving I think you'd find the boat unstable at high speeds. The sharp entry and narrow hull at the front is not going to be generating much lift, so the lift will be mostly generated from the aft portions of the hull. The hull does not have lifting strakes at all. You can see in this image that the hull is transitioning quite substantially under the aft porthole where the hull bottom is flattening and the hull chines are at waterline or below. This appears to be at approximately half of the boat length.

Also, you can see the forward end of what is becoming the keel. I think that this is going to have detrimental effects on the propeller efficiency if you're looking for higher speeds.

 

[sasqman]

Agreed with @Foxsea here. You might go a few knots faster with 200hp but it won't be the dramatic change you're looking for.

The sunset video you posted does look like you're technically planing to me but it's hard to tell for sure since you don't show the water flow at the transom. Planing is defined by when the boat is supported by hydrodynamic forces on the hull supporting the boat, rather than buoyancy. The rough approximation to determine when you begin planing is when you observe the water separating cleanly from the aft edge of the hull and the transom is not immersed in water (ie you could have an open hole in the transom and it would be dry). Still, at these low planing speeds you're still pushing a lot of water around and more power would push more water without a tremendous increase in boat speed.

If you put enough power on the hull to really get moving I think you'd find the boat unstable at high speeds. The sharp entry and narrow hull at the front is not going to be generating much lift, so the lift will be mostly generated from the aft portions of the hull. The hull does not have lifting strakes at all. You can see in this image that the hull is transitioning quite substantially under the aft porthole where the hull bottom is flattening and the hull chines are at waterline or below. This appears to be at approximately half of the boat length.View attachment 55390

Also, you can see the forward end of what is becoming the keel. I think that this is going to have detrimental effects on the propeller efficiency if you're looking for higher speeds.

Thanks Pineapple! Alot of insight and knowledge and I really appreciate it.

Paul

 

[Stosh]

I’d suggest you contact Bayliner directly for the most accurate answers to your question.
Stosh

 

[sasqman]

Not that this will add much to the thread as I think our decision on the repower is made............. maybe.... but videos are fun to watch. Top speed here was about 11 knots. The currents were pretty strong.

 

[Pineapple Express]

I'd say your technically planing...looks like the water is cleanly separating from hull and no water against the transom

 

[sasqman]

I'd say your technically planing...looks like the water is cleanly separating from hull and no water against the transom

Thanks for your thoughts. It feels like its planing and I do feel like more power would give more speed in optimal conditions like flat water or a head sea with 1 to 2 footers. But with the bow and the keel always being in the water, a following sea would still be uncomfortable (which it is now) as the bow does like to wander. But at hull speed in a following sea of 1 and 2 footers its manageble.

 

[tubber]

I made many trips from Ukee to big bank on an underpowered diesel Lifetimer at about 17 knots. We got there and got our fish usually.
If you could get to that speed with a bigger motor, I say go for it. Doesn't have to be brand new. You can still do the hull speed cruise to save fuel and while you're learning how the boat behaves in following seas.
If the handling of the boat changes, it won't be scary or dangerous until you get quite a bit faster than that, likely.

 

[Wild Bill]

When you are looking for an engine some manufacturers will have a larger displacement or higher gear ratio if you go a little bigger, my merc 225 came in 1.75/1 and I think 1.89/1. 1.89 better for big boat imo.

 

[Pineapple Express]

Thanks for your thoughts. It feels like its planing and I do feel like more power would give more speed in optimal conditions like flat water or a head sea with 1 to 2 footers. But with the bow and the keel always being in the water, a following sea would still be uncomfortable (which it is now) as the bow does like to wander. But at hull speed in a following sea of 1 and 2 footers its manageble.

Yeah, I can see what you're thinking. This has been sitting in my brain for a while now and I think that during the right conditions you could have a decent bump in speed (say from 12kn to 18kn). Obviously you don't have to go full throttle everywhere so with that in mind when you have following seas you'd back off the throttle.

As @Wild Bill mentioned above, different engines have different gear ratios and correspondingly take different props. The Yamaha F200 4-cyl takes the smallest diameter prop in the 200hp class (15"), so this would be my last choice of engine on your boat. The Suzuki DF200 4cyl takes a 16" diameter prop (comparatively huge!!) and has a big reduction ratio....probably a good choice for you. The middle ground of gear ratio is occupied by the Merc 3.4L V6 which can take up to a 16" prop (like the QuickSilver Enertia ECO prop). The Merc 3.4L V6 also weighs less than the Suzuki. The Honda BF225 has recently been revised but it's way too heavy. I know Suzuki has been gaining quite a bit of market share over the last few years, but this seems primarily due to price. The dealer network still seems sparse.

If I were in your shoes and planning to keep the boat I'd be considering the Merc 3.4L V6 in the 225hp rating for my #1 choice.