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I agree, there's what happens in the books, then there's what happens in real life. True knowledge is a combination of the two.
My understanding of motor height installation is that the anti-ventillation plate needs to be pretty close to lining up/parallel with the bottom center of the vessel. At least this is how things typically work with aluminum boat applications (the majority of my experience).
Is this still the general rule of thumb with these 16/17' whalers?
On a side note, as I've been drilling holes and filling with resin (for various hardware installation), I've noticed the rear of the vessel has water in it/damp. Mid hull to the front is dry. Does the rear end of these boats generally get damp as the years go on?
Again, you are trying to complicate things from the past.
KISS.
There are over 500 years of accumulated information that tells us where to mount the motor.
C'mon, there are only 4 holes to mount the motor in.
Mount it 2 holes up and forget about it.
Drill the proper holes as recommended and get on with your life and your enjoy your Whaler.
Sorry, I have to disagree in terms of trying to complicate things by asking questions. I'm trying to understand what the principles behind properly setting up a motor on one of these vessels are, if they are different than other vessels I've worked on/with. I've been a teacher for 20 years, education is what prevents further issues moving forward and helps people make decisions on their own.
Maybe some of that 'over 500 years of accumulated information' can explain the actual theory/principles on this, so that folks coming onto this website/forum can learn to think on their own, rather than depending on you or other regular posters.
So what happens when you aren't available anymore? What do people do then?
The old method of aligning the anti-cav. plate with the hull bottom is not true anymore. At least on these hulls with stainless props.
I am repeating this stuff from others with way more experience and from my personal experience.
Different subject, but after running alum props for 20 years, I switched to stainless because it came with the motor.
I am amazed that anyone uses alum. anymore except on a kicker.
There are a lot of opinions on prop material type. The majority of mechanics I have as colleagues tend to frown on them from the standpoint that the prop will withstand a hit, but even with slip hubs (or drive/shear pins), it ends up putting more stress on the gearbox and generally damaging the gearbox moreso than an aluminum which would just bend/break.
YES, SS props lend themselves to a little bit more performance, but for an extra 1-2 MPH, not sure if it's worth spending all that extra money not just for the prop, but to fix your gearcase if badly damaged.
Dealerships will encourage customers to buy SS because the profit margin is much bigger both with the prop sale and the ensuing repairs after a collision. I've yet to meet a dealership, even Mom and Pops business, that won't try to squeeze more money out of customers this way.
I have some experience mounting OMC engines on a "blue" Whaler 16'-7" hull, and it should be pointed out that these earlier boats had a shallower depth interior splashwell dimension. That is why the standard 8" vertical bolt spacing of the BIA bolt pattern does not work for the bottom bolts, and probably the reason why OMC invented the blind hole mounting system for the bottom bolts. It may have seemed like a good idea for the times, and for the kind of mostly aluminum props they had at the time, but for modern times it is a problem.
The information you have been given here is good - the engine has to be removed from the boat that those old holes filled. I have pruchased two used Whalers with OMC engines, and on both the engines were all the way down, blind hole mounted like yours (curse, curse), requiring removal and complete re-filling of the old transom bolt holes. I switched to Mercury power, but the same BIA bolt pattern applies.
The information you have been given relating to the bolt hole drawing on this site, and to use the "green" bottom holes is correct, and the simplest solution. This allows the bottom bolts to come into the splashwell, and receive the necessary washera and nuts. The bottom bolts should ALWAYS have the nut on the inside - the top bolts have the nut on the outside. This solution will automatically raise the engine 1-1/2", and is the maximum recommended for a lower HP engine like you have.
For best holding, a stainless prop may be required at this height, although a good design aluminum such as the mercury BLACK MAX or SPITFIRE 4 blade may also work. As a
Merc owner I admit I may be prejudiced, but I believe the Mercury/Quicksilver aluminum props are the best on the market and hold the best. They perform remarkably well for $100 they cost. I am not sure, however, they fit the gearcase bullet of the 70's. Check around first.
If you are worried about such a high mounting for a lower HP engine lilke a 70, you may also try the following. Measure your interior transom carefully, and see if you can use the "Yellow" bottom holes.
To do this, you probably have to raise the top holes a little higher than the standard 1-7/8", more like 1-3/8" or 1-1/2" If the transom is in good shape, you can do this, especially if you install the "transom stiffener bar" across the top bolts, about $20. I did this on my Outrage 19 - see photo
If the dimensions will work for you, this will result in an engine "raise" of more like 1" or 1-1/8", and will definitely allow use of an aluminum prop without slippage.
I told you there were folks on here with more direct knowledge than me. I am happy to see that he also agrees
with what you have been advised to do. X#%* except for the dang aluminum prop stuff.
Just kidding!
Appreciate the 'tip of the cap' to OMC, but one thing that I've learned is every company makes good motors and bad motors. And last time I checked, Mercury is still in business, OMC went the way of the doe-doe. There are 'those guys' out there who will say brands other than what they like stink, I'm not one of them. I kind of think of those folks as boat/motor racists! (smile)
I think Merc, Yamaha, etc all have good products, but you'll also find experienced mechanics and service techs from those companies who can tell you which generations/models of their product weren't that good. I can tell you a few for OMC too. Get talking with some of the top techs/service reps from the companies bass boat lines, you'll hear some great stories from all of them on which motors are turds and which things the engineers insisted on incorporating, even those the service techs told them before they went to production they wouldn't work!
I've heard good things about the quicksilver line of props too, so I'll look into that. Good info on the mounting bolts. The last owner really cut corners on this boat, so I was planning on putting some thick SS or aluminum plating across the inside of the transom for both the top and bottom bolts once everything is re-situated again.
What is the deal with SS props and whalers I'm picking up as a vibe in this thread? Diameter and pitch is the same regardless of materials. What is the difference?
Again - I know I'm a 'newbie' to these forums, but I deal with other mechanic related technical forums where I usually deal with retired mechanics or service reps from the actual manufacturing plants...so when I ask questions it's to understand the technical side too...not just the application.
The principle of raised outboard motor operating height to e.g., "two holes up" on your Boston Whaler 16 custom hull is to improve overall performance. This means you will have less draft, reduced drag, improved time to plane, reduced steering torque and effort, and overall improved speed and fuel economy.
There may be other issues with your hull that could be causing poor performance, i.e., porpoising. I noticed in your posted photographs that the below the water brass drain tube on the exterior of the hull is failed. There is no lip shown in photograph. You may have seepage of water into your transom core, and, as a result, you are running "transom heavy." Have you weighed your boat? The bare hull factory weight of a 16 was at 500 lbs.
