Undersized Motors?

PaulZ00

Hey all. I’ve been having issues with the performance on my 2003 29ft Rinker. Seems to run well, but just doesn’t grab and push the water the way it seems it should. It has twin Merc 4.3’s, 6 cyl with Bravo 3 outdrives. It just really struggles to get on plane and pick up speed. It also seems like the props are fighting each other. Steering gets tough at high rpms and the bow of the boat seems to move all over when it’s under power. Some have suggested that it’s a prop issue. Others think that the motors are way too small for that size boat. Thought I’d bring it here to the people who really know what they’re talking about to see if anyone had any thoughts? Is there any way to improve the “balls” on these motors?
I’d really appreciate anyone’s input. 
Thank you.

aero3113

@PaulZ00 , are you utilizing your trim tabs and trimming your drives correctly while on plane?

aero3113

Also, when’s the last time you did a complete tuneup on both engines?

PaulZ00

Aero, that’s an interesting question because there also seems to be an issue with the trim tabs as well.
It seems they slip as in I’m constantly having to push them down or adjust them every five minutes. It seems they don’t stay in a “set” position once I get them where I want them.
As far as trimming the drives, I always leave them all the way down unless I’m going shallow.
I just bought this boat at the beginning of the season and have yet to do a full tune up. I’m not sure when the last time the previous owner may have done it, but it seems to be a fairly well maintained boat.

aero3113

I would make sure your tabs are working correctly. When you go to start off you want your tabs and drives all the way down. Once you get over the hump bring your tabs fill up then trim your drives up till you find the sweet spot. You will see your speed and RPM’s start to climb as the drives come up. You don’t want to trim too far up, the boat will want to bounce (porpoise) and your props will cavitate.

PaulZ00

Thanks very much for that. I’ve never heard of doing it that way but I’ll definitely be trying that tomorrow.
I think my biggest concern is that it really struggles to get over the hump to even try that unless I have only a couple people on board.
But I’ll be giving that a shot regardless. Thanks again

aero3113

If your trim tabs and drives aren’t all the way down when you take off, the boat can struggle to get over the hump. Also, when you go full throttle move the levers at a moderate and smooth pace.

zaverin1

Paul you should just call me lol

zaverin1

Your dock neighbor Dave don’t know **** lol

zaverin1

My last boat was twin 4.3 with alphas and it was a beast 
I also question the bravo 3?
are you sure 

zaverin1

What rpm are you running at wot

LaRea

Have you checked the hull for fouling?  Around here (Potomac River) it has been bad this year.  I painted the bottom in March and already need to have the hull cleaned.  

The steering thing could be a worn steering pin.  If you hold one outdrive still, how much can you move the other one?  Shouldn't be more than an inch.  

laureniac1

Check out Hillmarine 4x4 props. Search the forum tons of posts on them. It’s like having a new boat with 4x4 props

PaulZ00

Zav!! Where you been? No. Dave and Curt are at a complete loss. Everyones sort of “something’s not right” but no one can really put a finger on it.
Come have a beer with us and we can figure it out.
The 4x4 props sound like something to look into for sure. 
I’ll also check out the hull when I take it out of the water in a couple months.
Did we even have a summer?
Thanks for everyone’s input. I appreciate you guys.

GMSLITHO

Like LaRea said You sure the bottom doesn’t look like this my brothers boat .the boat wouldn’t run faster than 15 mph when it should run 25 to 27 

Michael T

If you have twim 4.3s on a 29 foot boat with full fuel and a few people they have to be in top shape. I assume they are the newer 4.3 LX version. IMO that's a big hull, if loaded for a cruise, for 4.3s to handle. They are great engines. I have had two Rinker runabouts with them. That said they are, IMO, right "at the line" performance wise to do the job on a loaded 29 footer. As mentioned already the hull has to be clean, the engines have to be in top shape, the drives trimmed right with the drive ram shims in the correct performance location and you have to have the right props. You can get away with a lot if you have big engines not so when they are borderline IMO for the task.

zaverin1

I’m sure he had mpi engines 

zaverin1

Has

Michael T

Even better as reduces some of the tuning aspects.

PickleRick

Ditto on those 4.3 motors, outdrives, props and hull will all need to be top notch to get performance.  

Im sure those where "price point" motors but you certainly dont have price point outdrives


I bet with 2 5.7 motors in the same boat you'd notice better economy at crusing speeds.  Even a weak 5.7 puts down more torque than the 4.3.  Really not too much of a weight savings between the 2 motors either.

With that being said once its top notch again you'll get on plane just fine.  Some people bash the 4.3 but taken care of they last a long time.  My only comlaint is they drink fuel like a 5.7

Michael T

I agree 100% with @PickleRick - too many boaters don't realize how much a "borderline" performance motor(s) for their size/weight of boat costs in MPG and GPH. 

PickleRick

Bayliner was one of the worst.  Sticking 4.3 and 5.0 motors in everything.  A 20 ft trophy cuddy cabin with a 4.3 or a 23ft ciera(4000 plus lbs) with a 5.0.

I've seen seen some 25 ft bayliner boats with the 5.0



Granted i love the look of the 2455 bayliner hard tops.  Sadly the front windows dont open so that would be unbearable in the south all summer.  Ive heard the hulls suck for any off shore fishing due to the more cruiser like dead rise.  Looks like a fishing boat, handles like any other 24 cabin cruiser.  

Michael T

This may be the only time you ever read of me criticizing Rinker but a Rinker EC 360 left the factory with twin 5.0s in it. From what I hear it took a week to get it on plane. That said the dealer is rumored to have done this kind of thing a lot to hit as has been already said on this forum a "price point". Nevertheless IMO Rinker should not have let ridiculously underpowered craft leave the factory.....and - to be fair - maybe under its new management  Rinker dodesn't let that happen anymore. The customer is NOT aleways right!

Glassguy54

Hear Hear! There is no RE-placement for Dis-placement.

Michael T

@Glassguy54 100%. I believe that comment was authored by Rogher Penske's chief technician "Smokey Y." 

JoeStang

Everyone is definitely on the right track saying to get the tabs working right (and use them correctly), and keep the bottom clean.

I also wanted to mention that the higher speed steering issue is likely being caused by what is termed bow steer. It happens when the drive is all the way down once you're on plane. It causes the front of the boat to wander and need constant corrections. This would be made even worse if you had the trim tabs deployed.

There is a constant adjustment needed and fine tuning in the combination of drive trim angle, trim tabs, speed, and wave conditions. It takes practice and experience, and a LOT of people that have been piloting a boat for years dont understand fully what & how each of these factors does in the performance, ride, and handling of their boat. 

https://www.boatus.com/magazine/2014/june/staying-in-trim.asp

212rowboat

I get 4.3's... I dont get 5.0's... The 4.3 is nominally lighter and allows in tighter engine rooms... The 5.0 is actually heavier than a 5.7.. Just a little, but heavier. It is far from a square engine.  It produces more tq than the 4.3 but is hardly worth the weight. A 5.7 on the other hand, is a total different animal.  It can pack a punch.  A bored and stroked SBC can pack a lot of punch. Past that, BBC's puke torque and ought to be standard on anything 23+ feet long.  You can get the tq out of a SBC to compare, but only in a specific range that doesn't really matter to cruisers. 

The 5.7, okay. A 5.0 is a joke, though. 

rasbury

I'm guessing you never worked in sales Al, lol....

212rowboat

Alswagg said:

I could never understand why a 5.7 is a lot more money than a 5.0.  Essentially the same parts.  Sure the size of valves and the crank piston but essentially the same.  Cost to manufacture has to be exactly the same. 

when in a vehicle... i 'sorta' get it... the makers are bound by regulations and some of those stipulate a fleet average MPG that has to be below a certain number else they fave fines. 

ON PAPER using the stupid equation that is supposed to determine MPG's but falls flat on its face in the real world, the 305 gets better.  in reality, they are usually running higher RPM's and dumping vacuum (loading) which means they're rarely trimmed 'crossing zero' lambda... aka, running rich.  so.. not even in the real world is there a use for a 305... it's a head scratcher. 

PickleRick

The 305 replaced the 307.  The 307 was also a budget v8.  It doesn't make sense outside of pricing points in the sales room.

zaverin1

And this replaced all that junk lol