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Author Topic:   What Holes?!
elaelap posted 10-24-2003 08:09 PM ET (US)   Profile for elaelap   Send Email to elaelap  
[N.B. I posted this inappropriately in "General" in a topic discussing Dick's marina website]

You guys should get a laugh from the following:

I've been a CW member for a year now, and monitor the site on an almost-daily basis. I've read dozens--no, scores--of topics regarding the efficacy of mounting motors "up a couple of holes." Now here it comes: What holes?!

My old '71 Katama came with an ancient 55 hp Evinrude which was attached to the transom with toggle holes through the transom whatsoever. When I repowered, the guy who rigged my new motor told me happily that when he drilled through the transom for the four mounting bolts, the imbedded wood was sound (I doubt he was as happy as I!). We set up the motor so the [anti-] cavitation/ventilation plate was about 7/8 of an inch above the bottom of the tiny, U-shaped "keel" at the bottom of the transom. It's worked very well. My little 50 hp Yamaha four stroke jumps my boat out of the hole almost instantaneously, I cruise economically at 20 mph plus or minus a couple of mph, depending on sea conditions, and I top end at 30 mph GPS/5900 rpm.

Are there standardized holes in the transom of the newer Whalers, or are you and the others talking about some holes that I can't find in the tilt/trim bracket that's bolted to the transom?

I'm very pleased with the way my boat and motor are set up now, and not really thinking of raising my motor, but I'd sure like to know what everybody's talking about all the time...


lhg posted 10-24-2003 08:47 PM ET (US)     Profile for lhg    
Tony, I believe at about 40HP or so, the engine mounting holes in the ENGINE BRACKET are standardized, most brands, from about 1984 or so. This is the hole drilling pattern in the BOAT, so any brand engine can be fitted. With Mercury, there are five sets of 1/2" diameter holes in the bracket, for EACH of the 4 BOAT hole locations, two at top, and two at bottom, and any given set will conform to the NMMA standard. Hence the Mercury engine bracket has 20 holes in it. I think OMC used a slot for the two bottom mounting holes instead of individual holes in all 4 places. The five sets of holes have a standardized 3/4" centerline, so from the top hole to the bottom hole, there is 2 1/4" of elevation possible for the engine mounting height. If the engine is bolted on through the top sets of holes in the BRACKET, it is all the way down on the transom, usually giving the normal mounting height for boats that won't do over 40. On many Classic Boston Whalers, however, the Company recommended the engine be installed in the second set of holes, which would give a 3/4" lift. Follow?

Since I believe your Yamaha 50 4-stroke is a Mercury/Yamaha joint venture engine (the horror of it all - the engine short block is by Mercury), yours should have the 5 hole pattern at EACH engine mounting location. I know the Merc 4 stroke 50 does.

My 1984 Mercury 115's have this pattern. So when you read about someone raisisng or lowering the engine "a bolt hole", it means raising or lowering it 3/4", since the holes in the boat remain fixed.

kingfish posted 10-24-2003 08:48 PM ET (US)     Profile for kingfish  Send Email to kingfish     

It sounds in general that you are pretty close to where you want to be with the mounting height of your Yamaha on your Katama. It's possible that if you really wanted to absolutely maximize performance, you could raise it even a little further, but you're close to the point of diminishing returns. The proof of the pudding for you would be to observe the ventilation plate when well on plane; if it is well clear of the surface of the water, and you're not ventilating when you don't want to, you're cool.

I'm not specifically familiar with your Yamaha 50, but my bet is that is that like most newer larger (bolt-mounted) motors, if you look carfully at your transom bracket, you'll see that the bracket itself has a number of holes where the bolts that hold it to the transom can be placed, allowing the motor to be moved up and maybe down, without drilling new holes in the transom. Typically you have to pull at least two and sometimes all four bolts out to adjust the height, but when they go back through new lower holes in the transom bracket, they still go back into the same holes in the boat transom, effectively raising the motor by however many holes below the original holes in the transom bracket that the bolts now pass through.

I hope that is a little clearer than mud (but it cover de ground)-


kingfish posted 10-24-2003 08:51 PM ET (US)     Profile for kingfish  Send Email to kingfish     
That would be "John", and I think Larry and I were saying similar things at the same time, albeit Larry is more specific---
elaelap posted 10-24-2003 09:37 PM ET (US)     Profile for elaelap  Send Email to elaelap     
Larry and John,

Thanks to both of you for that. My confusion, as I suspected, stemmed from the fact that my elderly boat's transom had no holes at all to match up with the several boltholes and bolt slots in the motor bracket before the transom was drilled for my new motor. You know, I tell my clients that the only stupid question is the one not asked, but here it took me a year to scratch that itch. Merci.

And Larry, I ain't one of the Mercury bashers. I'm from the wobbly, wishy-washy liberal camp that would be happy with any outboard with a good warranty...but four stroke only, after my recent pleasurable experience.


P.S. My wife and I buy American when it comes to cars.

doobee posted 10-24-2003 10:13 PM ET (US)     Profile for doobee  Send Email to doobee     
I just saw the movie "HOLES". There were no Whalers in it though.
lhg posted 10-26-2003 07:49 PM ET (US)     Profile for lhg    
Tony - I was just ribbing you a bit.

But I do believe that you and Dick do have the identical 50HP 4-stroke engines on your boats, one gray and one black.
For 2003 Yamaha still offered this 57 cubinc inch 4, but Mercury has switched over to their new all Merc 50 HP 4-stroke, which Yamaha now uses for their 60, as does Mercury.

Anyway, getting back to "bolt holes", I just noticed that Mercury, at least, has recently changed their engine bracket on the new 30-60HP 4-strokes, and they now only have 3 sets of holes, not the five used on the larger engines. Evidently, they have decided that these lower HP engines don't need as much elevation potential, since they don't produce the higher top speeds.

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