Whats Your Method?

[Russell Bear]

What's your method to mounting the engine and mount in a fresh hull, either mono, cat or hydro? Just wanted to get some other opinions on how to get that perfect shaft alignment. What's your method?

Thanks........

 

[not2bright]

get alot of epoxy and smear it all over the engine and set it in the boat or at least thats how the guys on ebay do it

 

[Flyin Rat Sass]

it will cut down on vibration and make removal easier if you just smear it with silicone sealer

 

[mark poole]

LOL..ok guys...I think Russell has a good topic here. I have been reading a lot on this and find myself confused over mounting ideas and reasoning. Some people swear by the flex (rubber iso) mounts for more rpm. Others say that everthing mounted solid transfers more power and means more speed. And how does a flex mount affect alignment? Andy? Don? Gary?

 

[wswatzell]

I think (for what that is worth :blink: LOL) that a rubber isolation mount is to reduce the vibrations transferred to the hull. I can see that if the boat is not up on plane that a solid mount would transfer more power to the shaft initially, because the torque will roll the engine to the side as well as turn the drive shaft. However, it seems to me that once the rotation stops, the full power would be transfer to the shaft. Does this make sense, or am I totally off the mark?

 

[BradV]

Surely some of these answers are satirical.....

A motor that turns upwards of 20 000rpm isn't gonna be affected by a counter-rotating motion (ie the movement in the rubber mount), that would only turn an arc of a few degrees and then only when the motor is accelerating. mmm

So rubber mounts aren't going to reduce power as such, but they are great for noise and vibration reduction. They aren't essential for flex-drives I've found. Also the rubber eventually gets too sloppy so I personally find them a hassle.

Best system I've used for a mono is a one piece cradle made from high strength aluminium (forget the code) sitting onto bearers also made of the same stuff. The cradle mount bolts to the bearers with 4 large allen bolts.

I don't like two section engine mounts as they don't support the crankase.

I shape the bearers for a smooth contour to ensure maximum surface contact with the hull and get the right angle and height for motor-shaft alignment.

Drill lots of small holes into the underside of the bearers and prep the boat surface also. Use super high strength epoxy between bearers and hull, then when that is dry, cover the bearers with fiberglass matt and polyester resin.

 

[Don Ferrette]

Ok here goes-

Rubber mounted system, period. Here's why-

1- Solid mounts do nothing for absorbing engine vibrations, which there are alot of. There is NO SUCH THING as a "balanced" single cylinder engine. Don't let anyone tell you otherwise, it is physically impossible to do so. By nature the harmonics that develop from & during various rpm stages if not dampened will reverberate back thru the engine. Bearing failures, rod failures, cracked piston skirts, excessive wear, broken glow plug elements, broken headers, on & on.

2- Rubber mounts help isolate engine vibrations from becoming vibration harmonics in the hull itself. It is simply amazing the resonant frequencies developed in a vibrating wood or fiberglass hull. This is worse in a mono hull as it's very shape will amplify sound. I have seen a 3+ dB reduction in noise just by changing to a rubber mount. Not to mention the glue & bonding seams in any type of hull that fail when subjected to these types of harmonics, seen it too many times.

3- Solid mounts support the crankcase better? A total myth folks. These engine cases have gotten to the point that the strength of them is almost overkill in some instances. When was the last time you saw a mounting ear break off? Come to think of it, the only time I saw it happen was on a warped solid mount. A solid mount is actually worse for an engine as it does nothing to absorb the shock & torsional twisting motion of the engine. The engine will simply live longer in a properly constructed rubber isolation mount.

4- The rubber mounts get too soft & spongy. Really?? I guess I don't keep a boat long enough to see this? I've got mounts that have been in a few different boats & are still going strong plus even if you should actually wear one of these out, the isolation rubbers are readily available from places like McMaster-Carr & they're cheap. Then again I thoroughly clean the engine well areas of all my stuff when I'm done running. After the engine is flushed & oiled I have a spray bottle filled with denatured (rubbing) alcohol that I use to hose down the compartment of any oil & fuel residues. Maybe that's why I've never seen a rubber mount get "spongy"

Now there are some rubber iso mounts that are good, some not so good. My favorites are SpeedMaster & Aeromarine for standard type (4" & 5") rail spacing hulls. For outriggers the Roadrunner mount works well, but the rubber isolation grommets with 1/4" nylon mounting screws & spacers like in the Eagle SGX is my personal favorite. A nice combination of light weight & strength. The Octura "Hummdinger" mount is an example of one that's to be avoided, grossly overweight with that big underbelly plate. Would make a better bouy anchor. You don't need all that metal there folks, I actually drill out the mounting plates in some of my mounts to lighten them up & if someone will tell me how to post a pic on here I'd put one up to illustrate it. A good quality rubber isolation mount when properly installed & aligned will give years of trouble free service & help things last longer too. B)

 

[BradV]

Well I guess this forum is great for opinions and sharing experiences..

I have broken two crankcases because of incorrect engine support, where the motor was solid mounted but not in a solid one piece cradle or platform. Since going back to a solid cradle I've had no problems. Perhaps if each side of the motor was rubber mounted, and not solid mounted, it also might not have happened...

But I maintain IF you are using a solid mount then the cradle type or a solid connected platform is a must for engine longevity. That was the message I was putting across in my last post, as well as answering Russell's question on "how to get that perfect shaft alignment".

Was not entering into opinions Don about which is better solid or rubber mounted, as each have there merits and it's very model specific.

In my current boat I didn't have enough room for side hung rubber mounts, and I find vibration to be totally manageable as all fixtures are well engineered, bolts are threadlocked, radio gear wrapped in foam rubber etc etc. This boat has notched up over 60 hours of running time with no issues from vibration, no breakages and only normal engine wear.

So I don't think there is such a huge difference to be quite honest. If you've got the room, use a decent rubber mount or if you haven't, use a solid mount. Keep in mind rubber mounts have only appeared mainstream in the last 10-12 years. Guys have been running fast boats for a lot longer than that with solid mounted engines...

 

[Don Ferrette]

Well Brad to each his own. But there ARE big differences & consider the following -

You most likely wouldn't have broken either one of those motors had they been in an isolation type mount.

Why bother with "vibration management" as you call it with a solid mount? I don't need to locktite my motors down, I don't have to wrap my radio gear in foam rubber either.

Solid mounts do absolutely nothing to help with hull noise & they are proven to make it worse. In the day & age where we find it increasingly important to control noise, giving up 2, 3 or more dB to hull noise is just plain foolish.

Why carry all that weight of the solid mounts?? They are 2+ times heavier than a comparible rubber mount.

Rubber mounts have become "mainstream" for very good reason. The boat speeds have dramatically increased over the last 4-5 years. Anyone who thinks controlling engine harmonics & vibration is not directly relative to speed better look again. Any engine will be noticeably affected by vibration & harmonics caused by said vibration in both peak rpm & horsepower, this is a proven fact which any engine guru will tell you.

I've not yet seen a hull that I couldn't devise some type iso mount. I've also done them coming up from bottom where side space was critical. I'm glad it may work for you, but you are one of the lucky ones. I can't begin to count the number of problems I've seen ranging from poor running to breakage to noise to radio failures to whatever that was DIRECTLY attributed to the solid mount. In other words the mount system was changed & the problem went away. By all means best of luck to you but I will always stand firmly against solid mounts simply because of all the examples I've seen why not to use them.

 

[speakerboy]

ok . were slightly of subject here .. but i agree with don here. . i only do gas engines so i dont know about vibration of those nitro.s but ever seen a zenoah idle at 300 rpm ore lower .. its shaking baby .. and than there are moments when a engine stalls ore stop . than the vibration is even bigger sometimes the sparkplug can move more than a 1/4 inch ... we have to use the same vibro rubbers for our pipes too, otherwise the header will brake ore tear off at the exaust port ..

but back to the subject ..i ve built up about 10 hulls now and i try to follow the setup rules and c/g etc etc . this means i always mount the engine first , mostly with a small angle this way the cowl (mostly cats) will fill nice and i have acces to the underside of engine .(IV bag)

than with a mono i drill a hole in the transom and mount the drive ...than play a while with the flex cable and brass tube . now i can see the angle i need to bend in the brass tube . i bend the brass on my knee with the flex cable inside to prevent sharp bends and dinks .. i take my time here and bend it piece by piece . a long slow bend is better than a tight one .. some even say a S shape bend give even less drag .. than when i reached the perect line up i use some fast glue to fix it and than i use some epoxy and fiber to fix it stronger ..

in a cat /hydro / rigger its abit diff .. the engine is the first to mount .. than i mount the collet ore square drive .. and use a small flex cable ( old one) . now i put the flex in the collet and this way i can see where the flex must go trough the bottom . this area i drill 2 1/2 inch apart ..and take out the part between those drilled holes , now the brass tube can go trough, than i mount the strutt , again we can see the angle we have to bend .. one small difference with the mono , the brass tube need some straight tube at the end to fitt the strutt , and if u have 2 ore 3 inch straight horizontal brass tube , its posible to adjust the stutt a bit more up ore down ...

after i bend the tube . i fix it again with some fast glue and than fix it with epoxy .

the drive ore strutt are very important to mount at the right spot .. u dont want to mount it a bit left ore right becouse u glued in the brass tube in a wrong position , therefore mount the drive first ... same goes for the engine .. the flex cable and brass tube is just the link between them ..... if u do it it the other way u might end up with a diff setup than u had in mind ..... :huh:

good luck !

 

[GTR]

Hi Guy's

Have read this topic with interest - all in al I'd say I'm on Dons side. There is no good reason for solid mounting an engine. Maybe in the states iso mnounts are relatively new - the rest of the world has been using them in some form in boats for about 30 years. Noise is the underlying reson for their use as most countries have much harsher noise laws than you guys have had to contend with (until recently). I think the reality is a solid shaft provides more power to the prop than a flex - can you use this with iso mounts - yes but it has its own problems. The major drawback of solid shafts is getting a decent angle on the prop (without using universals).

Forgot to say when was the last time you drove a car without iso mounts? Their use is in response to NVH (noise/vibration/harshness) Doesn't this tell you something.

One point that has been briefly touched on is rubber mounting motors and then solid mounting pipes - DUMB. This does at least 2 things - transmits vibration to the hull through the pipe mount (remember pipe is a resonator) & places a lot of stress on the motor manifold and the welded joints of the pipe & coupler. Even racing motorcycles use rubber suspended engines and pipes - wonder why? There is an added bonus rubber mounting the pipe also makes it a little quieter.

If you follow the European examples they have hatch covers as well to stop radiated noise - carb induction noise etc. These guys are almost as quiet as electrics and yet can still get performance.

Yeah I am an advocate of Iso mounts - I think your crazy not to. There are different types of rubber available for iso mounts including a form of neprene for hot, oily environments.

All I have to say is have fun Quietly.

GT B)

 

[TimD]

No solid mounts for me thanks! I agree with Don and GTR.

The only reason I can think of at the moment for using solid mounts would be if you were trying to save every last gram of wieght.

 

[BradV]

GTR, seems to me a bit extreme to say you would "be crazy" to not use an ISO mount.

Seen lotsa boats work well with iso mounts, and lotsa boats work well with solid mounts.

As I've learnt from direct experience - it's not such a critical element to boat performance and reliability as you or Don imply. You can get around the issues of a solid mount, racers have been doing it for 30 years. That's my opinion, based on my experience, and I stick with it.

Seems to me this forum is about presenting a wide spectrum of information, so guys ain't it a bit blinkered to say there is a "wrong" or "right" way of doing something? Life just ain't like that...

Side point: Noise for me where I race my boat isn't problem, actually the tougher it sounds, the better for me!! That's why I don't run electric boats anymore! .. And.. Those iso mounts no good for my 12 sec car either GTR, have to run a solid connector on the lift side LOL and chuckles.

Merry Christmas guys.

 

[outboardman10]

Well, what is the best way to mount them to the boat? Like where the wood and the mount meet in a mono?

 

[outboardman10]

Well, what is the best way to mount them to the boat? Like where the wood and the mount meet in a mono?

 

[Russell Bear]

Good discussion here.

What is the best way to get that "perfect alignment"?. Should I mount the engine to the mount then drill the holes in the engine rails to attach the mount to the rails? And how in the heck am I suppose to get the holes drilled in the right spot with the engine attached to the mount. Maybe I'm thinking of doing things backwards? BTW, I am using a flexible mount.

 

[tracerbob]

Well, this is the way I do it. I first install the engine with a collect attached to it. Clamped in this collet is a short piece of drill rod with a couple of pieces of brass tubing slid over it to make up the difference in the diameter of the drill rod and the tubing I'm using for the stuffing box. I then mark the hull bottom where the drill rod/tubing touches. I remove the engine, drill a couple of holes in the hull to make a slot. I purposely make the slot a little wider than the tubing to allow for adjustment. Assuming I've already mounted the strut, I re-install the engine, grab the tubing and start shaping it line up with the strut and the drill rod on the engine (you want the stuffing box to slide over the drill rod/brass tubing spacers). When I'm satisfied with the fit, and leaving the stuffing box in place, I cover the hole on the outside of the hull with masking tape. I then cover the stuffing box inside the hull with epoxy and glass cloth. The tape keeps the epoxy in the slot and when I peel the tape off after everything cures, I have a smooth surface that pretty much matches the contour of the hull. And that's it!

 

[Don Ferrette]

"As I've learnt from direct experience - it's not such a critical element to boat performance and reliability as you or Don imply."

Well you can believe what you want, based on YOUR own personal experiences. I base my recommendations on the many problems that have been seen & SOLVED by eliminating these solid mounts in OTHER people's boats. And you already admitted you most likely would NOT have broken your 2 motors if they had been sitting in a iso mount so breaking motors isn't critical?? :wacko: :wacko:

 

[Don Ferrette]

"And how in the heck am I suppose to get the holes drilled in the right spot with the engine attached to the mount. Maybe I'm thinking of doing things backwards? BTW, I am using a flexible mount."

Russ-

Easy my friend! Mount the motor in mount with collet on motor. Position motor where you want it & trace a line around each motor mount on stringer. Take motor out & off mounts. Go back to hull & hold each mount half to each side matching your tracing pattern then mark & drill your holes, bolt mount halves in then motor in. Take a short section, maybe 4" to 6" long, of old flex shaft, slide it in collet. The shaft section will contact the hull & then bend along hull bottom. Start your hole just forward of where it starts to touch, then use a round file to open it up a bit at an angle, just enough that the same piece of flex cable exits in a straight line from collet thru the hull. Then take a short piece of brass tube the next size up from your stuffing tube, rough it up with 80 grit sandpaper. Then slide it over a longer piece of tubing same size as stuffing tube, then slide both over piece of flex shaft still in the collet & glass the outside tube in place. This gives you correct alignment & the ability to remove stuffing tube as needed. I never have really understood those who glass in the stuffing tube itself, makes it a real pain in the *ss to remove it if you need to. :blink: I do mounts & stuffing tube sleeve at same time which is why I went into doing stuffing tube as well.

 

[outboardman10]

So how do you hold your stuffing tube in place?