How low can motor be on transom and still be safe?

[The Grail]

I got a good deal on a used 1994 Evinrude Ocean Pro 200 (E200TZERK), but the problem is that it is a longer shaft than the motor I am replacing on my center console (30" compared to 22"). I've read many posts here on motor height, so I know the anti-ventilation plate should be about even with the keel. Long term, I will get a jack plate, or re-build the transom and make it higher (I know - or get another motor). I understand having a motor setting too low will cause drag, but is that the only concern?

My question is this - for the short term, with my AV plate 8 inches below my keel, is there any danger?

 

[Chris1956]

Re: How low can motor be on transom and still be safe?

is the old motor a 20" shaft (Longshaft) or a 25" shaft (Ex-Long shaft)? A 30" shaft is XXL shaft, BTW. 22" shaft doesn't exist...

Performance will certainly drop. You may get more spray, and the boat may ride nose down. Is there a way to transplant the good parts of the new motor to replace te bad parts of the old motor?

 

[Silvertip]

Re: How low can motor be on transom and still be safe?

Having the AV plate 8 inches too low also means the prop is 8 inches too low and the chances of prop strikes is raised significantly. This does not make for a great handling or performing boat. Do it right and avoid the problems. That means proper lower unit, jack plate, or rebuilt transom. The jack plate makes the most sense, especially if the transom is sound. Besides, the jackplate provides some additional set up benefits.

 

[Chris1956]

Re: How low can motor be on transom and still be safe?

I stand corrected, the Johnnyrude model guide specifies a "Y" shaft, which is 22.5 inches.

 

[The Grail]

Re: How low can motor be on transom and still be safe?

Sorry for the inaccurate information - the old motor is a 20" shaft - 135ELT74B, 1974 Johnson, so interchanging parts isn't an option. The AV plate of that one was even with the keel. With the new motor set as high as possible on the transom, the AV is 8" below. The jack plates I've seen online raise only 5", which would still leave me 3" low. That's better, but will that make much difference? I appreciate your responses.

 

[ondarvr]

Re: How low can motor be on transom and still be safe?

Sorry for the inaccurate information - the old motor is a 20" shaft - 135ELT74B, 1974 Johnson, so interchanging parts isn't an option. The AV plate of that one was even with the keel. With the new motor set as high as possible on the transom, the AV is 8" below. The jack plates I've seen online raise only 5", which would still leave me 3" low. That's better, but will that make much difference? I appreciate your responses.

It will only leave it 3" low if you mount it 3" low, just mount it higher.

 

[The Grail]

Re: How low can motor be on transom and still be safe?

Unfortunately, I can't just mount it higher. I need to go up 8" but most jack plates only go up 5", which still leaves me 3" low. Just trying to decide if that's worth it, for the short term. Anyone heard of jack plates that have 8" of vertical adjustment?

 

[crb478]

Re: How low can motor be on transom and still be safe?

I think he is trying to tell you to mount the motor higher on the jack plate and then take advantage of the 5" of lift.

 

[tmcalavy]

Re: How low can motor be on transom and still be safe?

Without seeing your transom and the type of hull you have any answer we give is pure speculation...although true in general principle. If your prop is 8" deeper than the keel, the chief danger is hitting underwater obstacles and damaging the motor or boat in the process. Performance wise, it will slow you down and the boat will handle "heavier" and not respond well in tight turns at speed. If you can't shorten the motor leg, the only options I see are replacing the motor for a short shaft or raising the jackplate mounting point so the 5" the jackplate provides puts you somewhere in the ballpark of correct motor height. Problem with jackplates is they sometimes require mods to the boat, so that your steering and control cables are cocked down or up too much...that, too, can affect performance and cause problems. Post some pix of your boat/transom so we can see what you are dealing with...open a free account on photobucket, post your pix there and then provide a link to the pix in your future posts.

 

[ondarvr]

Re: How low can motor be on transom and still be safe?

Unfortunately, I can't just mount it higher. I need to go up 8" but most jack plates only go up 5", which still leaves me 3" low. Just trying to decide if that's worth it, for the short term. Anyone heard of jack plates that have 8" of vertical adjustment?

Most jack plates can be mounted at different heights, plus the motor can be mounted at different heights, so you should be able to make up the 8".

 

[The Grail]

Re: How low can motor be on transom and still be safe?

I bought a manual jack plate today, and I plan on installing it and the motor this weekend. I believe I'll be able to make up most of the difference. I'll take some before and after pictures, and post them. Thanks for the comments!

 

[The Grail]

Re: How low can motor be on transom and still be safe?

Well, it took a while, but I finally got everything set up and got out on the water last week. Thanks for all your input. I haven't made that many postings, but I've been viewing this site for four years and it is always a wealth of information.

I installed the jack plate as high as possible on the transom, set the jack plate at it's highest setting, and mounted the motor as high as possible. It ended up where I thought it would, gaining me 5" and leaving the AV plate about 3" below the keel. I'm sure it's slower than it would be if the motor were higher, but I haven't seen any other major problems. I have a fish finder and the water is very shallow here in Southwest Florida, so I am constantly aware the water depth and my limits. At some point, I will need to rebuild my transom. If I like the motor and keep it that long, I will make the transom higher to accommodate the motor. Here are pics:
http://photobucket.com/TheGrail