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My 1966 measures 22" from top to bottom of keel, but as Tom has said this is a 20" transom. Forget that measurement and follow the pattern they are referring you to. I have raised mine to third hole.
Thank you, mtown, for your message. It explains a lot.
When I first reported that my Whaler has a 22" transom, people on this thread responded with the helpful advice that if I measured my transom properly (vertically not horizontally; straight down not at an angle) I'd see that it is, in fact, 20". But no matter how I measured (it never occurred to me to measure diagonally or horizontally since motors are mounted vertically), the transom came out to 22", not 20. The mechanics at the shop and I didn't know what to make of the certainty among posters that my transom was 20" when, with the boat in front of us, no measurement we tried came within 2" of that length. I knew in my heart that the probability that Joe and others were wrong was essentially nil; still, it's difficult to ignore facts in front of your face and take it on faith that somehow that transom is 20". I began to think that Joe was correct in thinking that perhaps my boat is not an authentic Boston Whaler.
Your post clear it up. We were both correct: the transom measures 22", but motors should be mounted as if it were 20".
Sadly, it's too late now and the motor has been mounted with CMC jack plate. So I'm out $300 for a plate I don't need.
Question is what to do now.
I took the boat out yesterday and oh-my-god is that motor amazing. When I finally found water calm enough to put it to full throttle I was blown away -- literally almost -- by the speed and acceleration. Frankly, I don't see a reason to travel at that speed on a boat, other than for the pure thrill, which is substantial. To those who urged me to get this motor: bless you. It's quiet, clean, and a monster at full throttle.
However, there are issues that, I think, are related to the mounting. Specifically, I think the motor may be too low. For example, at full speed I can barely turn the wheel. It was difficult to turn the wheel when my Johnson 70 at full throttle; this is 10 times harder. Also, the motor looks very low: when getting up on a plane the back of the hood appears to almost be in the water. Getting up on a plane itself feels weird. I need to use one trim (low) to get up on a plane gradually (it was too choppy to accelerate quickly), and a different trim (higher) to cruse comfortably. Finally, and I'm not sure if this is diagnostic, but looking back at the motor while planing I saw a lot of water bouncing off the rear of the boat (not sure how to explain this; it appeared as if water was somehow being thrown against the back of the boat even though the boat was moving forward at high speed). My only explanation is that the water must have first bounced off something else (the motor?) and then bounced off the boat. Seems that a motor mounted too low might explain a few of these issues.
Presumably the jack plate permits relatively easy vertical adjustment. Question is, what is the correct height for the motor and how can I estimate what that is? With the motor trimmed all the way down: the "chin" of the motor is 6.5" above the top of the transom, and the bottom point of the motor is 39.5" below the top of the transom. On my trailer this puts the skeg just 2.5" off the road which is lower than it was with my previous motor, though I'm not sure that's an apples-to-apples comparison.
Any suggestions on how to estimate the right height for the motor? Unfortunately, the distance between my "boatyard" and the water is 10's of miles, so small-increment trial-and-error is awkward.
Two seemingly unrelated issues are:
1. The control lever (new) has large areas of movement in which no change in rpm occurs. From a slow forward speed I can push the lever down two to three inches with no response from the motor. The problem is that the huge range of rpm variance is now represented by a small range of lever movement making it difficult to make minor adjustments in rpm at the higher speeds. Presumably, this is a simple adjustment the mechanics can make.
2. While the motor is quiet during idle and low rpm, the boat vibrates much more than it did before. It's not just that the railing rattles at one rpm, and something else rattles at a slightly different speed; you can feel the hull vibrate under your feet at all rpm Perhaps this is just the effects of a larger motor on the boat, but I thought I'd raise it in case you have ideas about how if might be fixed.
Again, many thanks to those of you who have contributed to this thread.
always trim your motor so there is no pull on the helm. It is easy to get that point, just adjust the tilt or trim so you can remove your hands from the wheel. If that is causing your prop to vent then something is wrong.
A pic taken from sideways of the AV plate in relation to the keel will eliminate all the guessing. As said by J. Kriz, the plate should be higher than the lowest point of the hull, by anywhere from 1.5 to 3.5 inch.
I assume you got the CMC manual jackplate, with probably 4 inches of setback. Crank up the jackplate until the AV plate is 2 inches above the keel or as high as the jackplate will go and then run some prop tests. What prop is on the engine now? To test the prop, hit WOT and trim out until she cavitates then record your RPMs. My guess is that the engine is buried, the jackplate is probably all the way down and with the engine mounted all the way down on the jackplate it's worse than mounted all the way down on the transom. The height of the motor above the transom doesn't matter, what matters is the height of the AV plate above the keel. That is the measurement you need to care about.
The vibration may fix itself if you get the motor set correctly. At idle what are the RPM's?
The CMC plate is manual, with 5.5" setback. I opted not to get a new tach with this motor so I can't report anything about rpm without getting engine reports. Depending on cost, I think I'll ask them to install a tach while they're making the other adjustments. Can anyone recommend a basic model?
I though the 90's required a basic system check gauge that usually has a tach? If not just get whatever base model they have, because without a tach it's hard to determine what the engine is doing. Sound is a very unreliable indicator of RPM's or performance.
You can adjust the engine yourself with a friend and some simple tools. If your taking it back to the dealer, you want them to mount the engine on the jackplate so when the jackplate is at it's lowest point, the engine AV plate is 1- 1 1/2 inchs above the keel. My guess is that they won't be able to do that because of the setback, so in that case they should mount the engine as high has they can, probably 3 holes up which will probably leave the AV plate at or still below the keel.
On my 18 with the 8 inch setback on the jackplate, that means the engine is mounted 3 holes up and I still have to crank the jackplate up 3 inches to get the right height. On my personal page, 4 photo from the bottom, that is how your engine should look when your on plane and it's mounted at the correct height.
