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Author Topic:   Johnson 70 on Montauk
MikeB posted 09-18-2001 05:16 PM ET (US)   Profile for MikeB   Send Email to MikeB  
I just purchased a new 1999 Johnson 70 to repower my Montauk. Does anyone have this setup? If so what pitch prop do you recommend? What should I expect from this setup? The motor has four bolt holes at the top and bolt slots at the bottom of the motor mount. There is a set of tapped holes in between. The slots are too low to use for the Montauk. Do you mount with two of the top holes and the two tapped holes? Thanks for any info.
TightPenny posted 09-18-2001 05:29 PM ET (US)     Profile for TightPenny  Send Email to TightPenny     
The mount on your 70 is the same as the mount on my 2001 90hp and the 1997 60hp that I originally used.

You use the two tapped holes for the lower mount. I suggest using anti-sieze on the bolts when you install. Saves headaches later if you have to remove the engine.

Just line up the anticavitation plate with the line of the bottom of the boat. This is basically the engine just sitting on the transom.

You can make a template for the holes by using a large piece of paper (I used a blueprint) and a crayon to trace the hole location from the back of the engine mount. Use the crayon the same way you would to trace impressions on paper. Cut it out and set it on place on the transom, mark your holes and drill. Or I suppose someone sells a template.

simonmeridew posted 09-18-2001 08:19 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
I have the identical setup with my '84 Montauk: a 1999 Johnson 70. What a beautiful engine! Starts great every time, idles nice, quiet, doesnt smoke, oil injection is handy and works. I got a water pressure guage for mine just to keep an eye on the cooling. Mine came with an aluminum 17" pitch wheel; when I found a pile of rocks when I didn't expect them, I bought a 17" stainless steel Rapture wheel. I sent the bent prop in to get repaired--one blade was bent back some and a little rock rash on the others. The steel one "thumps" a little more going into gear, (I think), but it's really smooth at all speeds. It has three vent holes in the hub which you can plug with little plastic cones to experiment with hole shot etc. I think the RPMs are a little lower on the stainless prop: maybe 5400 rpm vs 5600+ on the aluminum one. Same top speed about 35 mph by GPS. Incidently I like the little "U" shaped transport support the motor has. I don't want to think about the skeg dragging for 30 miles after I hit a bump in the road so I always rest the motor in the up position supported etc.
MikeB posted 09-18-2001 08:34 PM ET (US)     Profile for MikeB  Send Email to MikeB     
Is your prop a 13 1/4 x 17?
whalerron posted 09-18-2001 11:53 PM ET (US)     Profile for whalerron  Send Email to whalerron     

If you are replacing a Johnson with a Johnson, there will be no drilling involved. OMC had the foresight to make the hole patterns the same. You will need to use the threaded holes for the lower bolts but all the holes will match up if the motor being replaced is a Johnson.

Bigshot posted 09-19-2001 11:29 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Actually most engines today in the same "range" have the same bolt pattern as OMC. Suzuki started this in the late 70's so the person would not balk at that issue(OMC was #1 back then). I would mount that motor up about an inch on the transom instead of on the transom. The motor should redline at 6000 so high 5's with a light load should be Ok. I would try a 13x17.
simonmeridew posted 09-19-2001 07:58 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
Yes the new Rapture Stainless prop is 13 1/4" diameter by 17" pitch. Made by Michigan Wheel. Midwest propeller service has the best prices especially through their website which had a special deal I think 10% off regular price and free shipping on the prop repair end of things, but also it seemed like the best price on the new Rapture too. It was on my doorstep in Vermont within a week. BTW the aluminum prop, which is I assume OMC original equipment on the motor, is stamped 14 X 17. It just barely clears the fin thing on the lower unit.
Hope this helps.
bdb posted 09-20-2001 08:11 AM ET (US)     Profile for bdb  Send Email to bdb     
I too am running an OMC 70 on my Montauk. Prop is SS 13 1/4 x 17, tops out at 5600 with a moderate load. Top speed is usually about 35.

My engine is mounted 2 holes up. This allows the bottom mounting bolts to be placed in the lower mount "slots," at the very top of the slot. This precludes the ability to position the engine any lower on the transom, but as you will note from a million other posts, you want the engine mounted higher.

Set-up works great...wouldn't change it.

Kim posted 09-28-2001 12:22 AM ET (US)     Profile for Kim  Send Email to Kim     
bigshot I had a 1982 omc (johnson) on my montauk17. when I replaced it with the 2000 suzuki df 70 the bolt holes DID NOT line up. had to fill the the two upper ones as I rember. or the bottom ones ? can"nt rember but I did have to fill two holes.
Whalerdan posted 09-28-2001 04:39 AM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
Kim - Did you consider a set back plate rather than redrilling your transom? Seems like if you did this one side of the plat could be matched to your new engine and the other could match the holes in the transom. I know it can be repaired (the transom) but I just don't like the idea of putting more holes in there.
Kim posted 09-28-2001 08:45 AM ET (US)     Profile for Kim  Send Email to Kim     
whalerdan, The holes were so close that I did not feel it would be a problem. I filled them with West System and I got some larger fender washers (s/s) for the inside. You can't see the filled holes. I also liked the idea of the fender washers as surface area instead of the small ones that came with the engine.
I think it was the top holes that did not match. The motor works very well in place of the old OMC but it is a heavy weight! As to your ? no I did not consider a plate.
OT: Does any one know or heard from george ( GVISKO ) I would like to ask him about the way he flushes his df70...
thanks kim.
jimh posted 09-28-2001 09:31 AM ET (US)     Profile for jimh  Send Email to jimh     
There are also transom plates that can be used on the inside to add more strength to the engine mounting. I do marvel at the durability of four stainless steel bolts to hold some of these big engines on the transom.

Bigshot posted 10-01-2001 05:07 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I can see filling in 2 holes. This was probably because they mounted the original all the way down or up and now you wanted more range or different height. Reason being we had a 1972 rude 100 on the 19 revenge that was replaced with a 1982 Zuki 140 and it bolted right up. i have only repowered a few boats and usually with way different(old merc to Omc) or just from a 50 hp to a 70. Someone else might have more definate experience. I am pretty sure though that most engines above 50 or 70 hp have the same pattern. look at a 50hp Yamaha and it has a real wide plate so it mounts to where a 70 and up OMC will, etc.
gvisko posted 10-02-2001 06:29 PM ET (US)     Profile for gvisko  Send Email to gvisko     
kim iam still around
i flush my dfi70 from factory flush port
motor not runing . dealer says this is proper way . i hope he is right . how do you flush yours ?

gvisko <><

Kim posted 10-03-2001 08:12 PM ET (US)     Profile for Kim  Send Email to Kim     
bigshot; it sets the same in highth(s/p) the two top holes that I had to fill were from side to side not up or down.again the 1982 70 hp johnson with a 2000 suzuki DF70. It was no big deal to do !
made a carboard templet/ I cut a piece of cardboard about the size of the mounting plate . then pur a light coat of oil on the engion plate/ then put the cardboarn on the engion this marks the hole patern if you do not move it thats how I found out I had to fill the holes. then I used it to drill the new ones.

GVISKO , (George) take a look at your owners manual page 37.
the port on the side of the engion
is for flushing in the slip!
you should be useing duck tape when you flush your df70page 38.
if you can'f yours I could copy mine and fax it to you. suzuki recommends flushing with the flushing attachment (ear muffs)
not the port in the side inless in the slip. thanks for the reply. may I ask what the hrs on yours? over 400 now on mine...

gvisko posted 10-03-2001 08:51 PM ET (US)     Profile for gvisko  Send Email to gvisko     
kim i only have about 50 hrs on motor
real happy so far my montauk is in a slip
when i flush it i will use ear mufs when i take it out dealer says it is not needed
but i will do it anyway . how? is you motor with 400 hrs ? what should i expect


Kim posted 10-04-2001 01:00 AM ET (US)     Profile for Kim  Send Email to Kim     
GVISKO (George) sorry to here that you only have 50 hrs. I'm sad that you don't have time to take her out more!. maybe then you will see what I talking about in the gas milage.So we are on the same page 1 can you give me the heading on page 37 the top right side, of your owners manual.
thanks. kim.
Kim posted 10-12-2001 01:07 AM ET (US)     Profile for Kim  Send Email to Kim     
MikeB please excuse me / with respet to you & your post, ok
to george , TTT ... (GVISKO)
I did not think you could answar this.......................................................................

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