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Author Topic:   Repowering 1973 17 Katama with 2003 Merc 90
NHKatama posted 10-10-2002 10:18 AM ET (US)   Profile for NHKatama   Send Email to NHKatama  
I am repowering my 1973 17 Katama with a 2003 Merc 2 stroke Saltwater engine. (I just sold the original 1972 merc 50, it was still running strong) I plan to detail the entire boat over the winter, any Ideas on this are welcome with comments or suggestions. Also reading some of the posts on here, it appears that there are several options on the right height to mount this new engine, I am looking for suggestions on the right height to mount this engine, also should I consider having my shop mount this engine onto a Jack Plate, if so what brand do you recommend. I only want to mount this engine once. Also would you recommend ss prop. Background on the load we often have onboard 4 people a 50 quart cooler, 13 gallons of fuel, lifejacket, duffle bag with jackets etc. Any help on this is appreicated, Thanks PT
Bigshot posted 10-10-2002 12:03 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Do the jack plate....manual type any brand, and then you can "adjust the engine height for max performance without unbolting it. Do a SS prop if you do not constantly dredge the bottom. I would put off buying the engine until you are ready to use it, your warranty starts from the day you buy it, not launch it. Actually it starts the day the dealer mounts it, if the bought from that dealer. If you buy it from somewhere and take it home, it starts at purchase date.
newt posted 10-10-2002 01:37 PM ET (US)     Profile for newt  Send Email to newt     
Bigshot, the merc warranty sucks either way, because it is only one year. So no matter how you look at it, he will only get one boating season out of the warranty since it is already the end of the season up here in the N.E.
NHKatama posted 10-11-2002 05:59 PM ET (US)     Profile for NHKatama  Send Email to NHKatama     
Thanks for the info on the jackplate, I will have the shop mount the engine on one. Do you pick up any performance if you use one with an 8" (or so) setback to move the engine back a bit or am I better off just using one that is 3 to 4 ". Also, I have a deposit on a 2003 90HP that the dealer will mount and then start the warranty, when they install it in the spring. I think I got a good price on this Engine at $4,300.00, it is a 2003 90HP saltwater 2 stroke. I liked the Honda 4 stroke, but at $9,000, i can burn alot of extra gas with this new engine. And I did have good luck with my last merc, so I figured I would stick with another. In case any of you think this price is too good to be true, I bought the motor at the boat show, and the dealer told me later that they marked the wrong price on the engine, but agreed to honor the price since I had already given them a deposit.
waltuh posted 10-11-2002 07:57 PM ET (US)     Profile for waltuh  Send Email to waltuh     
You might want to take a look at a Yamaha two stroke 90hp because it weighs 260 lbs vs the 308 for the Merc 90 two stroke. Also, some boaters are upgrading to four strokes and trying to sell off their old two strokes and the two stroke market seems to be more of a buyer's market. I found an '89 Yamaha 90 w/ remote throttle control & Yamaha led 3" guage that looks like new, inside & out for $1000.00 plus it came with a 1969 boat & trailer. The local town transfer station here in NH would only accept the boat if cut up into four foot sections, a big nasty job, plus they charge $80.00/ton. Anyone know of a legal method of disposing of a 17' fiberglass boat which has been stripped of all items worth saving in the Winnipesaukee area? The trailer, a two axe-4 wheel 17', 1969 roller bunk style is for sale but it comes with the booby prize boat, yuck.
jimh posted 10-11-2002 08:05 PM ET (US)     Profile for jimh  Send Email to jimh     
When our sailing club disposed of a 23-foot Pearson sailboat we made arrangements with some folks to have it sunk as an artificial reef (for fishing habitat).

A Milwaukee SAWZ-ALL will make fast work of any fiberglass hull, once you find the right saw blade combination. We used to have an in-ground swimming pool with a fiberglass liner. A week or so of summer evenings and a SAWZ-ALL and the pool liner (16 x 32 feet ) was in a pile of pieces to be thrown out in the trash for the next few months. A guy quoted me $5,000 for that job. Cost me about $10 worth of saw blades.

Bigshot posted 10-14-2002 09:53 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Buy another garbage can and start chopping. By Thanksgiving, she'll be gone and so will the itching.
NHKatama posted 10-15-2002 11:31 AM ET (US)     Profile for NHKatama  Send Email to NHKatama     
Well I guess there are not too many out here that want to talk about repowering. As for considering another Engine. I already have a deposit on the merc. In regards to the 2 cyle engine market being dead, I do not think so, several folks like the off the line power of a 2 vs 4 stroke, and with EFI the fuel economy is very close to a 4 stroke. Also I sold my 1972 merc 2 stroke for $850, that is about what we paid for it new in 1972, so all and all not too bad.

Well anyway, I believe I picked the right engine at the right price $4300 for a new engine seems pretty good, if anyone knows for a better price for any brand new 2003 please let me know. I am still open to suggestions with regard to mounting height jack plate etc. Also, I never had a tach on this boat does anyone out there have a katama, and have ideas as to the best place to mount tach. Also would like to hear from anyone that has recently repowered a 16'7" hull as to their performance numbers. Thanks ~~~PT

Montana posted 10-15-2002 12:53 PM ET (US)     Profile for Montana  Send Email to Montana     

Donít let anyone talk you out of that Merc 90. IF there is one thing Iíve learned from this site and talking to local boat dealers is that people are more opinionated bout outboard makes and models then they are about anything else including automobile manufactures. I recently repowered a 1966 Nauset with a Merc saltwater 90 and couldnít be happier. Iíve only got about 12 hours on mine so far but I believe the performance of this engine to be top shelf. She starts every time with out any hesitation and Iíve only seen her smoke when first starting her and even then Itís not worth mentioning. I also agree with you about the power coming out of the hole-shot. My family likes to water ski so that was an important factor for me when it came time to repower. I took my time on making up my mind and did a lot of research before I made my decision on what to buy. I didnít get quite the deal you are getting but I think I still got a good deal. I got a lot of compliments from the boat mechanics when they took her out to dial her in for the first time. Iím not sure how fast Iím getting out her yet as I donít have a GPS or anything to reference against. I do know that when I get her all trimmed up at WOT I tend to hang on to the steering wheel a little bit tighter. My guess is that Iím getting the upper 30ís and low 40ís at WOT.

Bigshot is right about the Jackplate. The first problem I ran into was the mounting holes were completely different for the new Merc verse my old 85 Rude. I didnít like the idea of drilling new holes so I went with the jackplate. Actually it might have been Bigshot who suggested it to me. I went with a 4Ē set back on a fixed jackplate. The manufacturer of the jackplate eludes me at the moment but if you want I can find out for you what Iíve got. If youíre also interested I can look and see what mounting holes they used on both the jackplate and the engine. I also talked with the boat mechanic about going with an 8Ē set back but they really didnít think I would get that much more performance out of the boat. They seem to think it really didnít come into play until the 18í or bigger boats.

At any rate go with the Merc 90 and I think youíll be more then happy.


newt posted 10-15-2002 01:40 PM ET (US)     Profile for newt  Send Email to newt     
Ditto what Montana said.

I just re-powered my '84 Montauk with the '03 merc 90 2 stroke. The hole shot is awesome - about 1 second to get on plane.

I have gotten 44 mph [statute, measured by gps with a little current helping me :)]. I am running the basic Mercury Aluminum 12.75 x 21 pitch prop.

My tail end is feeling a little sore now after learning what you paid for that motor! I was too impatient to search for such a good deal.

lhg posted 10-15-2002 06:34 PM ET (US)     Profile for lhg    
I think they marked the price of a similiar looking 75 on your 90. Most 90's are about $4800 bought right.

Consider using a 20" pitch Merc Laser II prop. With any aluminum prop, you will not be getting the optimum performance out the engine.

whalerron posted 10-16-2002 12:43 PM ET (US)     Profile for whalerron  Send Email to whalerron     
NHKatama - My Minot has the same console as your Katama and I had the same problem with the tach. That console will only let you mount the tach horizontally or vertically. I built a small box out of starboard and mounted it to the console slightly to the right of the wheel and back to the windshield. The box is just large enough to house the tach and it holds the tach at a 45 degree angle. This mounting allows me to easily read the tach whether I am standing or sitting. I thought about making one out of mahogany but I simply didn't want another piece of wood to care for. I could send you a picture if you are interested.

I just repowered with a new Johnson 90 and this is my first tachometer too. I don't know how I ever got along without one.

- ron

tabasco posted 10-16-2002 01:54 PM ET (US)     Profile for tabasco  Send Email to tabasco     
Great price on the 2003 90 HP. When it come time to repower I will email you with my requirements. :-)
NHKatama posted 10-17-2002 10:19 AM ET (US)     Profile for NHKatama  Send Email to NHKatama     
Whalerron, sounds like a good solution to mounting a tach. I would love to see a pict of the tach box that you made, also, do you have a compass on your boat, and if so where did you locate that. The console on the Katama is not set up to easily accept gauges. Hope to hear back from you and see some picts. Thanks, Pt
whalerron posted 10-21-2002 08:55 PM ET (US)     Profile for whalerron  Send Email to whalerron     
NHKatama, I emailed you pictures of my tachbox which is made out of starboard. It's a great idea if you don't want another piece of wood to "keep after".

- ron

Clark Roberts posted 10-22-2002 09:20 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
NHK, you will have a fast and economical rig with a Merc 90 2S. I have have had several 17's with 90 mercs (6cyl, 3cyl 71 cubes, 3cyl 84 cubes) and the current 3 cyl (84 cube) engine, set up right (on jack plate) and spinning a 20-22" pitch prop (my last had a 20" high five) will hit close to 50mph and tear your lips off on accelleration out of the hole. The engine is simple (with no detachable heads), reliable and very, very quiet at speed. Interesting that the 90 will actually outperform the 4 cyl 100hp (just a 3cyl with extra cyl added) in top speed and handles better also. I have run these combos in side by side tests and the 90 pulls ahead every time... Larry has noted that even the merc prop/performance data shows the 90 as the faster engine. Maybe the extra weight absorbs the 10 hp difference and also it's possible to get a 99hp ninety and a 91hp one hundred... blah, blah, blah, ... man do I get long winded or what! Anyway, hope you have many happy hours with the 90 and Happy Whalin'... Clark.. The Old Man...SCN
thebone12 posted 10-22-2002 04:03 PM ET (US)     Profile for thebone12  Send Email to thebone12     
Stay away from the jackplates, its only a lever for your engine to break your transom.
baltica posted 10-23-2002 05:09 PM ET (US)     Profile for baltica  Send Email to baltica     
I have a 1970 katama and purchased a 2001 Merc 90 last year, am quite happy with it.
My dealer installed a 19" prop on it, however, so I have not been able to run it at full throttle yet (it tops out at about 35 mph at 5500 rpm). I was curious what other props you have tried on similar boats.
As for jack plates, can anyone recommend a good brand that's not too expensive?
Clark Roberts posted 10-23-2002 08:01 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
I use the T & H Marine ( 6" set back manual adjust with single center jack screw.. a shade under 300 bucks.. it's almost as narrow as the mounting plate of the outboard and does not block the transom well drain holes.. I have used a dozen of these and currently am using two. There are other good ones also, I'm sure, I just like this one best of all... Happy Whalin'... clark.. SCN
Montana posted 10-23-2002 08:41 PM ET (US)     Profile for Montana  Send Email to Montana     
thebone12, care to elaborate?
lhg posted 10-23-2002 08:49 PM ET (US)     Profile for lhg    
I have twin Merc 115's, weighing a total of 610 lbs, set back 10" on brackets on an 18 Outrage. After almost 10 years, the transom is not yet broken, nor even shows signs of gelcoat stress cracks. See photos in the Reference section to survey the damage.
newt posted 10-23-2002 09:11 PM ET (US)     Profile for newt  Send Email to newt     

I run a 21" prop on a montauk with a Merc 90. Top speed is low 40's at 5500 rpms.

Landlocked posted 10-24-2002 10:51 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
I have the same setup/results as newt


lhg posted 10-24-2002 03:05 PM ET (US)     Profile for lhg    
To make those 16's/17's "scream and fly" with the recent Merc 90's, you should mount the engine in the middle holes, and use a 20" pitch Merc Laser II prop. You won't believe the difference.
newt posted 10-24-2002 04:57 PM ET (US)     Profile for newt  Send Email to newt     
lgh, what could we expect with the prop change? As it is, hole shot is more than enough. Litterally, if I dont warn my passengers before launch, they would go flying off the stern!

I could use a little more top end, if only for bragging rights!

Wild Turkey posted 10-24-2002 05:10 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     
Forum member thebone12
has made comments about jackplates before.

In that thread and in this current thread, he chooses not to elaborate on his comments.

thebone12 posted 10-24-2002 05:40 PM ET (US)     Profile for thebone12  Send Email to thebone12     
I just go back! The reason that I do not like jack plates is because I do alot of rough water boating. Have a 350 engine on an older transom in rough water is enough stress but to give it a 6 inch level puts ALOT more stress on the transom. Anyone can hold a 9.9 outboard up, but now extend your arms and try and hold the outboard up. Same concept. If you are boating on calm water then it is O.K. but on a large bay, lake or ocean you will hurt that transom, first stress cracks and then you suck the washers into the transom and finally if the transom is weak it will fail. I have seen this happen alot of the great south bay of LI.
lhg posted 10-24-2002 07:32 PM ET (US)     Profile for lhg    
Newt - The Laser II prop will give you more top end, in spite of the lower pitch. It will also give you more hull and bow lift, which decreases drag and improves speed. An aluminum prop will flatten out over 35mph under load, losing pitch. The Laser II won't. These things really turn on for mid-range and top end speed.

See the photo of props in JimH's "Propeller Basics" reference section article. Note the advanced design of the Laser II profile. The aluminum prop pictured is 23" pitch, and the Laser is 22" pitch. Both are the size to fit the Merc 75-125's.

newt posted 10-24-2002 08:12 PM ET (US)     Profile for newt  Send Email to newt     
If I find a good deal on a used Laser II I might try it out, and use the aluminum as a spare. If my tack is correct, I can still get better than 5500 rpms, so I know the motor is capable of faster speeds.
whalerron posted 10-24-2002 10:56 PM ET (US)     Profile for whalerron  Send Email to whalerron     

I went out in the rain tonight, crawled under the tarp and took measurements of that tach box. I made up some drawings which I emailed to you.

- ron

NHKatama posted 10-25-2002 01:45 AM ET (US)     Profile for NHKatama  Send Email to NHKatama     
Thanks Ron for the drawings, you have been very helpful. I am going to make a tach box for my Katama, in fact I am going to start it next week. I may make it out of mahogany, though. I have some nice mahogany stock kicking around. Not sure though, because as you said more upkeep.

Again thanks for all your help, hope that I can repay the favor sometime. Also, next time you are up in NH would love to get together and but youa couple of beers, and take you for a ride on the fastest Katama in NH,

NHKatama posted 10-25-2002 01:56 AM ET (US)     Profile for NHKatama  Send Email to NHKatama     
IHG , explain what you mean by middle holes on engine,, sorry but I have not picked up my new motor so have not seen the mounting bracket yet. Also that sounds good with regards to the 20" Laser II. I think I will go with that prop. Do you or did you have a merc 90 on a 16'7" hull and if so did you have it on a jackplate, and what is your opinion with regard to the jackplate on this boat. Sorry for all the questions, but thanking you in advance, ~~~~Pete
NHKatama posted 10-31-2002 11:16 PM ET (US)     Profile for NHKatama  Send Email to NHKatama     
I am still working on this repowering project.

I think I will mount the engine on a manual Jack Plate. I was thinking of either the Cook (CMC) or the T&M Marine, with the center screw to adjust engine height. If anyone has had experience with either one of these plates, please feel free to give me your opinion. I have had some people tell me just to mount the engine right to the transom using the middle mounting holes. Any comments on this? I am trying to weigh all the options before I drill any new holes into my transom. Also, I was planning to fill the old holes in the transom with hardwood dowels set in apoxy, again comments are welcome.

hope to hear back from you all soon, ~~~Pete

Wild Turkey posted 11-01-2002 02:37 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     

I have been very impressed with the performance of my 1989 Montauk with the jackplate installed. I would highly recommend the installation.

Here are some pictures of my setup with a CMC manual jackplate:

NHKatama posted 06-04-2003 11:32 PM ET (US)     Profile for NHKatama  Send Email to NHKatama     
Anybody install a 6" Jackplate on a 16'7" hull lately?

If so, how far above the bottom of the boat in inches should the Cavitation Plate be.

Ive been told around 3" is good, but looking to see what height, every one has gotten the best all around performane out of.

Thanks all, ~~~~~Pete

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