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Old 07-14-2004, 01:19 PM
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Default Testing for bad stringers or rotten transom...? late 80s 21' Mako

Good day all,

I've found a late 80's 21 Mako sitting neglected on another island and thought it might be a nice project.

It's not really feasable to contract a surveyor to get out there, pay his trip and his hours to get a professional opinion.

Are there any tests that I could do myself to check for rot in the transom or for broken stringers?
What are the obvious signs and what are the more subtle signs?

Sha also has a 250 SWSII yammie on the back can a novice hire the equipment needed and do a compression check.

thanks in advance for any answers
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Old 07-14-2004, 01:38 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

A 250 on a Mako 21....fasten your seat belts!!!!

I would be very concerned about the transom. That is a lot
of weight and HP on that boat....
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Old 07-14-2004, 01:56 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Tap on the stringers w/hammer, listen for soft sound, tap on transom and various places on bottom of hull w/mallet, again listening for less than solid sounds. A compression guage is cheap, screw in 1 plug hole at a time and turn over motor. All six cylinders should be within 10%.
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Old 07-14-2004, 02:08 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Pep Boys and Checkers sell the air compression guage testers cheap. This is a quick, simple test to do. Instructions come with the box. You just need a strong battery, a spark plug socket, and the OEM data of what is optimum and acceptable pressure. But a motor that old is probaby a throw away if you are thinking abot going offshore for safety reasons.

If there has been standing water in the hull for a long time the stringers and hull could be suspect for water intrusion and rot. You can tap the glass softly and will notice a non solid sound if there are soft spots, and any dark or yellow discoloration under the glass will tip you off too. Cracks anywhere on the glass on the transom is another no no, and any discloration around screws under the water line would also probably send me packing.

But, an late 80's Mako Hull could be in very good shape in most instances, and be worth up to $5K with a trailer IMHO.
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Old 07-14-2004, 02:30 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

if i'm not mistaken the yammie looks like a late 90's model judging by the cowling.

other than the compression check, what else should i look out for on the engine?

thanks for your responses so far.

p
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Old 07-14-2004, 02:42 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Sea trail.
Does she start easy, run smooth, hit 5500 rpms, smoke a lot, have fouled spark plugs, have rust on the engine or in the oil on the lower unit. Does the engine trim and lifter sound smooth. Has the prop been dinged badly, etc.
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Old 07-14-2004, 05:37 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Does a ninety year old women have wrinkles? You bet!

Does a twenty year old Mako have rot? You bet!

Marry either one with a great deal of care!
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Old 07-14-2004, 07:09 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

go to www.classicmako.com and see what the solution might involve
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Old 07-14-2004, 07:33 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

When doing a compression test. Hot battery, remove all the spark plugs, open the throttle wide open,
screw the guage in each cylinder and write down the max compression after spinning the motor.
Transom chack.
lock the motor down with it tilted up. Have a buddy grab the skeg of the motor while you watch the transom.
Have the buddy lift and push down on the sheg of the motor. You watch for movement of the transom.
Then use a plastic headed mallet and do the sound testing all over the transom.

Stringers are harder to do .se you can't see them. Look for cracks along the bottom. This may be a pain, as the boat may be setting in the weeds.
I found a crack in the bottom of my boat after the fact. It was hidden by the trailer bunk.
The plastic matllet may or may not tell you the true shape of the stringers.
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Old 07-14-2004, 07:52 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Max HP on that boat is 230. Mine has a 225 yammie.

There is no difference in weight between the 225 and 250 yamahas it is the same block.

You should be able to get the exact year from the MFG plate on the starboard stern. It that one is missing there should be another one in the anchor locker on the port side.

Good luck and keep us posted would love to see some pictures.
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Old 07-14-2004, 08:19 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

with the transom do as suggested with a buddy hangin of the motor skeg .. for the stringers eye sight along the chimes while the boat is sitting on the trailer this may tell u if the timbers have gone soft ..if they have then most times u will see bows in the chimes ...other way of course it to offer to purchase to an agreed price if all is sound underneath the deck.. and then cut the deck out..and negotiate...
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Old 07-14-2004, 10:03 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

I have a mid 1980's Mako 21.. Most here know my story... Check her out good. A yamaha 250 on that hull should run about 50 mph. I wouldn't expect any more than that. Good power for that heavy old boat. I have a good knowlege of what the innerds of the boat look like.

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Old 07-15-2004, 08:10 AM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Others have offered good advice. Yes it's over the max horsepower, but doesn't really matter except to the insurance company.

The reality is that there is very high probability that water is in the transom. I've never seen one that old drilled that didn't weep some water. If you can hang on the motor and the transom doesn't move you can hope it's good for a few years. My transom weeped a little when I put a new transducer on 3 years ago (89 hull). No problems yet, but I know that someday I'll be bothering Ringleader with dozens of emails when I try and replace it. It's still solid as the day I bought it so I still think I've got a couple years or more.

Along with compression don't forget to check the lower unit oil.

Also, remember to pull the kill switch when doing the compression test.


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Old 07-15-2004, 12:08 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Eddie !! of course I know your story Big Pappa! I followed your renovations on classicmako.com like a soap opera. I even emailed you once about how you learned to do all that stuff. I still haven't ordered the videos but definately will do if I get this puppy.
How's the mrs ? I take it you have other things on your mind now cuz you aint updated that page in months.

To all you gents, thanks for all the advise. I don't know when I'll get over there again but if I do will definately try and get some pics or if the price is right will just grab her.

I'm another who grew up on mako's. you just gotta love 'em
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Old 07-15-2004, 12:19 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Quote:
warthog5 - 7/14/2004 7:33 PM
When doing a compression test. Hot battery, remove all the spark plugs, open the throttle wide open,
screw the guage in each cylinder and write down the max compression after spinning the motor.
I know that on OMCs you should use a remote starter ($20) and leave the ignition switch off and/or remove the kill lanyard so as to not put high energy through the coils ...
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Old 07-15-2004, 01:20 PM
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Default RE: Testing for bad stringers or rotten transom...? late 80s 21' Mako

Thanks... I haven't touched the boat in 4 months. Too much going on with the house construction and some work on the father-in-laws boat. I plan to break free of the house for a while after this weekend and hopefully finish up work on the father-in-laws little boat... Then maybe I can get back to work on my Mako21. I'll try to get some of the little things done through the end of the summer and when it cools of I can make some major headways again... But we will have a new member of the family in October, so that might slow things down a bit as well.

The Mrs. is doing just fine. She hasn't really had a bad day yet. She's at 6 months right now and is about 37" around... She started at 23"! Unfortunately she'll have to endure Louisiana Summer while carrying all that extra weight and girth.
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