New to the forum with my first question bout motor mount hight.

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I am the new owner of a 2000 208 Grady White with a EFI 225 Saltwater Yamaha. The boat slightly used and was rigged by a dealer in Wisconsin 25 years ago. The owner that I purchased it from used it for a taxi to go to and from a cabin on an island in Green Bay. Super clean boat and rub=ns great. After I purchased it I started doing some service work to the engine. Knowing that one of the weak areas of the older Gradys was the transom to top deck sealing. When I was inspecting the sealing area I noticed the motor is mounted in the #1 hole. Seems low to me. I would suspect the motor should be mounted in hole 2 or 3 with a big gear case 225Hp Yamaha. I'm looking for input as to what hole others 208 Grady owners have the motor mounted in? Thank you in advance for any information provided.
Brian
PORT-A-GEE
Gold Looper
208 Grady
 
Gearcase size is not important. Besides, that gearcase is not different than all the rest. It's really all about the anti-ventilation plate compared to the hull bottom. There are tons and tons of threads about this - if you wanted to read up on it you can search. There's also tons and tons and tons of threads about this on the internet and it's all basically the same - the specifc hull is typically of no consequence unless it's an oddball hull design, which the Grady is not.

The anti-vent plate, roughly speaking, should be level to slightly higher than the hull bottom. Check that and report back.

But... how does it run? Can you get max RPM (or close)?

If it's lower than the hull bottom - go ahead and move it up and experiment to see what works best for you.
 
DennisG01 said:
Gearcase size is not important. Besides, that gearcase is not different than all the rest. It's really all about the anti-ventilation plate compared to the hull bottom. There are tons and tons of threads about this - if you wanted to read up on it you can search. There's also tons and tons and tons of threads about this on the internet and it's all basically the same - the specifc hull is typically of no consequence unless it's an oddball hull design, which the Grady is not.

The anti-vent plate, roughly speaking, should be level to slightly higher than the hull bottom. Check that and report back.

But... how does it run? Can you get max RPM (or close)?

If it's lower than the hull bottom - go ahead and move it up and experiment to see what works best for you.
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Thank you for your post. I agree with all said. This is not a new concept for me. I owned and operated a small marine service shop in the midwest and if I have rigged one outboard I have rigged a hundred. I was a certified Mercury marine and OMC service technician and rigged outboards for a number of years. Many performance bass boats but also Bluewater boats Whalers, Hydrosport, Aquasport, Stratos, all similar to Grady's with 25" transoms and larger HP 2 stroke motors ( 80's 90's and early 2000 boats and outboards. Yes there trial and error to find the sweet spot on best mounting hole and matching a prop that would keep the motor hooked up. Once that is found it is a repetitive install if hull and motor are of like kind. I always used the rule of thumb that starting position (cavitation plate) 1" above the centerline of the hull bottom on a V-hull or 1" above the pad if the hull had a stern pad. Then I would work up a hole at time and compare performance and see if the prop starts to blow out at a given speed or on a turn. On Bass boats I would live with some blowout because of performance gains. On blue water boats I would not because of the rougher sea conditions the boats would be operated in.

I can do this with my new to me 2000, 208 Grady that has been operated on the water for 25 years mounted in the # 1 hole with cavitation plate slightly lower than the center line bottom. It was rigged by a Grady White dealer in Wisconsin that I am familiar with because I purchased a Boston Whaler from them in 2002 and the had the motor mounted in the #1 Hole too. Boston Whaler recommended #2 hole in their rigging instructions. I placed it in the #3 hole and had better hole shot and picked up an additional 1mph between #2 hole and #3 hole. 3mph increase from #1 to #3. That is free speed ! I remember this because of the discussion I had with the dealer!

My main reason for posting this thread is to try to skip the experimental work. The boat is 25 years old and there are a lot of 208 Gradys out on the water. I figured that the experimental work has been done. There are many Grady owners that have found the sweet spot and I was posting this to find it. Best hole mount while I have the motor hanging when I am inspecting and resealing the bang plate.

If you own a 208 with a 200 or 225 hp what mounting hole are you running in?

Brian
Gold Looper
2000 Grady 208
 
"Experimental" line of thinking - understood. What you're REALLY looking for here is someone that has TRIED both/multiple holes to see the difference. Not someone who says "I have it in X hole and it works great".

FYI... anti VENTILATION plate, not cavitation. Look up the definitions - they're two entirely different things. :) :)
 
DennisG01 said:
"Experimental" line of thinking - understood. What you're REALLY looking for here is someone that has TRIED both/multiple holes to see the difference. Not someone who says "I have it in X hole and it works great".

FYI... anti VENTILATION plate, not cavitation. Look up the definitions - they're two entirely different things. :) :)
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Yes and No to your question.

I have it in the X hole and it performs better that it did in the Y hole and I have found that the performance and handling has proven to be better in the X hole. Good answer:

I have had it in the top hole and then changed to the second hole and noticed a difference for the better in performance. Good answer:

I have the motor mounted in the third hole from the top and the boat performance is good and I don't experience any blow out. Good answer:

I know that raising to the second hole from the top will give better performance and not cause blow out. My question is leading more to mounting to the third hole.

The boat has been operated for 25 years in the first hole and I do know not best mounting hole to run it in. In my past experience the 1st hole "cavitation plate" slightly below the hull is to much drag and performance is compromised. My rule of thumb is "cavitation plate is 1" above the bottom of the hull. I just purchased this boat and engine. It has less than 200hr of run time on the motor and the owner did not use it much, primarily used it for a boat taxi to go to his cabin on an island in Green Bay.

Sorry if this seems like a complicated question. It wasn't meant to be. It may be a question that is not important to Grady owners. Dealer rigged it and it must be correct. Based on my experience I'm going to raise it to the third hole and hope for the best. Worst case I will have to lower it to second hole. I thought I would ask the question in this forum first. Known good experience responses are always helpful.

FYI: In my 25 + years of working has a certified Mercury marine technician and (Defunct OMC outboard marine technician) a cavitation plate, also known as an anti-cavitation plate or a cavitation plate fin, is a component typically found on the lower unit of an outboard motor or sterndrive. It is a flat, horizontal plate that extends horizontally from the lower unit, often just above the propeller.

The primary purpose of a cavitation plate is to improve the performance and handling of the boat by reducing cavitation and improving water flow around the propeller. Cavitation occurs when the pressure on one side of the propeller becomes too low, causing water to vaporize and form small air bubbles. This can lead to a loss of efficiency, reduced propulsion, and increased propeller noise.

I do agree that raising the motor to high or having the "cavitation plate" closer to the water surface will cause ventilation. Yes cavitation and ventilation are to different things. In my description I never referred to prop cavitation. I referred to "Blow out" Blow out is a term that many marine technicians say when the prop has to much ventilation (getting to much uncontrolled air in the blades). So if you want to refer to the cavitation plate as a Anti-ventilation plate I know what you are talking about. In the marine industry the known name for the plate that I described as the "cavitation plate" is Cavitation plate. You can use your terminology and I will use mine based on the industry standard. :):). Thanks for the response.
Brian
 
Late Again Grady said:
So, you came here to post your resume and dispute others suggestions??? Welcome.
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No, I did not join to post a resume and dispute suggestions. If I disputed a suggestion as to what hole the motor should be mounted I apologize. The one suggestion that I was given. My response back was "Thank you for your post. I agree with all said. This is not a new concept for me."

My question was, what mounting hole are 208 Grady owners running their motors in? Simple question. My question was not, teach me how to determine which hole to install the motor in.

My question was not to teach me the difference between Cavitation and Ventilation.

If I offended members I apologize. I simply responded to a post : FYI... anti VENTILATION plate, not cavitation. Look up the definitions - they're two entirely different things. :) :) I was not disputing a suggestion. I was responding to a FYI statement .

It's probably best to just close this thread. Sorry guys, I didn't mean to ruffle feathers. I did get a PM from a member of Grady Life FB Grady White owners club. Second hole with a 150 HP Yamaha HPDI. No information for larger Hp motors. I will try the #3 hole and see what happens. If I experience blow out I will mount in hole #2.
Brian
 
Not my own experience but I recall seeing posts (perhaps it was THT) where 208 drivers using a 2.8L F200 or 2.7L F150 were setting up on the third from the top hole with good results versus factory setup at the second hole. Unfortunately a quick search did not turn up those posts.

My own 208 experience with a 2.8L F200 is that the boat might benefit from raising the motor one hole but have not yet tried as I am happy with low to mid rpm range boat handling and fuel burn in and around Barnegat Inlet NJ. My performance numbers are similar to another similarly set up 208 using the same prop, Powertech SCE4 14x14. Happy to give more details, shoot me a PM.
 
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It's good guys - I didn't take any offense to the vent vs cav part. It's a good discussion to have. But to your line of thinking, Brian, cav is definitely a different thing than we're taking about - and this is not to compare, but I've also been in the marine industry for about 30 years.

Truth is... most manufacturers get the cav vs vent plate terminology wrong. You are correct that cav is about a low pressure thing. No argument there. But typically cav is caused by improper blade geometry or damage to a prop - which has absolutely nothing to do with the plate.

Performance loss due to the introduction of air is, plain and simple, ventilation. Hence, the proper name for the plate is the anti-vent plate as the plate has no impact on blade geo or damage.

Back on point - it sounds like you're on top of things. And I also agree with what you said about looking for someone with similar hull and engine (although having the exact same setup isn't important - just close). That will provide the best answer. BUT... you'll need someone that has had the engine in various holes AND has good data to back it up. Otherwise, it's just internet talk

That said - keep in mind that these hulls are not about, nor designed to be about, top end speed. Nor are the props designed for that. They are designed for handling chop. As such, trying to eke out a few MPH may come at the expense of a loss of performance at cruising speeds where the prop starts sucking air in certain conditions. My point here is that it's often better to be a tad lower than a tad higher.

In my opinion, if you're happy with the performance and you can get at/ ear your max RPM trimmed out at WOT - let it be and go boating . Although, there's certainly NOTHING wrong with tinkering on a boat, either!!!
 
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