70 horse Johnson cooling system modification service bulletin

[midsized johnson]

Thanks Bubbakat for the SB. I installed the water outlet fitting at the top of the exhaust cover which makes more sense to me as the location for the tell-tale water outlet. When I ran the motor, I had a big increase in water pressure (10 lbs at idle). I still had the flow restrictor in the end of overboard indicator. I removed it and flow was more normal (2-3 lbs at idle). I believe the flow restrictor should be removed permanently. Anyway, for those interested, here's pics of the finished product.<br /><br />Port side of motor with overboard indicator and tubing at top of exhaust cover:<br />

<br /><br />Stern view, "tee'd" (white connection at top rear of exhaust cover)the outlet hose to water pressure gauge.<br /><br />

 

[willamettejeff]

Re: 70 horse Johnson cooling system modification service bulletin

Just curious, did the SB say to remove the tell-tale restriction? I would think removing it would reduce the amount of water flowing through the exhaust manifold to sufficiently cool the exhaust.

 

[OBJ]

Re: 70 horse Johnson cooling system modification service bulletin

The point in making the modification is to ensure the block gets filled with water by filling through the bottom of the block and venting out the top through the tell tale hose. With a full block, water press should increase.

 

[willamettejeff]

Re: 70 horse Johnson cooling system modification service bulletin

OBJ, I understood about mounting the tell-tale water outlet high on the block just not sure about the desirability of removing the tell-tale flow restriction.

 

[midsized johnson]

Re: 70 horse Johnson cooling system modification service bulletin

Here's the SB that Bubbakat sent me. <br />

<br /><br />It doesn't mention flow restrictors. When I installed a waterpump kit a few weeks ago, the instructions told me to remove restrictor and put a rubber grommet at the hole where telltale hose comes out of the cowling. This grommet seemed to restrict flow somewhat, but I kept the restrictor in. Now I'm thinking of running without it.

 

[the rebel]

Re: 70 horse Johnson cooling system modification service bulletin

Not to Hi jack your thread MSJ, but were you having cooling problems before you did this? Or is this something to prevent air pockets in the water jacket? I thought the flow restrictor was for the purpose of allowing the block to fill before it would pass through the tell tale. <br /><br /> Bubbakat has some good SB's. Does anyone know if you can pull these up on the net? Or where to find them. Thanks. BWJ

 

[clanton]

Re: 70 horse Johnson cooling system modification service bulletin

Everyone i do the mod on, i remove the restrictor. I will also recheck the bulletin.

 

[the rebel]

Re: 70 horse Johnson cooling system modification service bulletin

Ok I just can read the SB in that picture, it looks like it is about trapped air in the block. Makes sense. BWJ

 

[OBJ]

Re: 70 horse Johnson cooling system modification service bulletin

Sorry if I'm being dense on this.....it's just not registering what restrictor is being removed. Dosen't say anything in the SB about removing a restrictor. Someone please help get my gray cells re-aligned.....

 

[midsized johnson]

Re: 70 horse Johnson cooling system modification service bulletin

"Not to Hi jack your thread MSJ, but were you having cooling problems before you did this? Or is this something to prevent air pockets in the water jacket? I thought the flow restrictor was for the purpose of allowing the block to fill before it would pass through the tell tale."<br /><br />No cooling problems, I'm running it pretty high on the transom for skinny water, so I wanted to make sure that no air got trapped in the top end. Even if I mounted the outboard low, I didn't like that water came out at the bottom of the water jacket, I'd rather know that water got all the way to the top cylinder for cooling. As for the restrictor, I'm probably wrong but I think it is meant to keep water on the exhaust manifold a little longer to maintain a higher running temperature.<br /><br />"Sorry if I'm being dense on this.....it's just not registering what restrictor is being removed. Dosen't say anything in the SB about removing a restrictor. Someone please help get my gray cells re-aligned..... "<br /><br />The flow restrictor on this outboard was clipped into the cowling and the telltale hose plugged onto it inside the cowling. It's real obvious that it's a restrictor when you take it off, it's like taking your thumb off the end of the garden hose when you're watering plants or hosing off your boat.

 

[OBJ]

Re: 70 horse Johnson cooling system modification service bulletin

Thanks MSJ....I always just called it the tell tale nipple. ( I must still be living in the dark ages.... Shouldn't hurt anything to remove it with the modification.<br /><br />Just looked at it on the parts list...it's called "Nipple, Engine Pan"......

 

[the rebel]

Re: 70 horse Johnson cooling system modification service bulletin

Originally posted by Mid-size Johnson:<br />[QB] "Not to Hi jack your thread MSJ, but were you having cooling problems before you did this? Or is this something to prevent air pockets in the water jacket? I thought the flow restrictor was for the purpose of allowing the block to fill before it would pass through the tell tale."<br /><br />No cooling problems, I'm running it pretty high on the transom for skinny water, so I wanted to make sure that no air got trapped in the top end. Even if I mounted the outboard low, I didn't like that water came out at the bottom of the water jacket, I'd rather know that water got all the way to the top cylinder for cooling. As for the restrictor, I'm probably wrong but I think it is meant to keep water on the exhaust manifold a little longer to maintain a higher running temperature.<br /><br /> right on, I am in the process of raising my 75 horse 2 inches. My stabilizer is about 1 1/2 inches below the hull on my boat. How did it work out for you? I have a 16' aluminum bass boat. Like the skinny water, better bass holes in the hard to reach places. BWJ

 

[midsized johnson]

Re: 70 horse Johnson cooling system modification service bulletin

Originally posted by Big White Johnson:<br />

Originally posted by Mid-size Johnson:<br />[QB] <br /> right on, I am in the process of raising my 75 horse 2 inches. My stabilizer is about 1 1/2 inches below the hull on my boat. How did it work out for you? I have a 16' aluminum bass boat. Like the skinny water, better bass holes in the hard to reach places. BWJ

It seems MidSize and Big White have something in common. I'm running my 70 on a 16' Weldcraft with pontoon extensions on the stern (these really help on the hole shot). I put a manual jackplate with 5" of lift (raised 4")and another setback plate so that now it's about 10-11" back from transom. I have the motor set on it's bottom hole on the bolt pattern. A friend of mine that builds boats told me that every 12" of setback allows for 2" of lift. She runs pretty freakin' skinny and I got her up on plane in a foot of water the other day (I would've preferred to drift out, but there wasn't any wind).

 

[the rebel]

Re: 70 horse Johnson cooling system modification service bulletin

Originally posted by Mid-size Johnson:<br />

Originally posted by Big White Johnson:<br />

Originally posted by Mid-size Johnson:<br />[QB] <br /> right on, I am in the process of raising my 75 horse 2 inches. My stabilizer is about 1 1/2 inches below the hull on my boat. How did it work out for you? I have a 16' aluminum bass boat. Like the skinny water, better bass holes in the hard to reach places. BWJ

It seems MidSize and Big White have something in common. I'm running my 70 on a 16' Weldcraft with pontoon extensions on the stern (these really help on the hole shot). I put a manual jackplate with 5" of lift (raised 4")and another setback plate so that now it's about 10-11" back from transom. I have the motor set on it's bottom hole on the bolt pattern. A friend of mine that builds boats told me that every 12" of setback allows for 2" of lift. She runs pretty freakin' skinny and I got her up on plane in a foot of water the other day (I would've preferred to drift out, but there wasn't any wind).

Yeah we got something in common, but your boat looks like it is a whole lot lighter than mine. I've got a 16' Fisher Marsh Hawk with front and rear casting decks and twin consoles with a bench seat. About the time I try to get mine out of the water it goes to porpoising. I thought about trim tabs to help the hole shot and the porpoising problem. I've been doing some work to it, just got through doing the Boyesen reeds and new kits in the carbs. Wanting better(lower) idle and better hole shot. On the muffs it has helped clean up the idle, haven't put it in the water yet, but it does sound more responsive. My boat is not fast, on a good day it has hit 42-45. I thought it should do a bit better. Running a 13 3/8 X 17 aluminum prop. What about you?

 

[midsized johnson]

Re: 70 horse Johnson cooling system modification service bulletin

Originally posted by Big White Johnson:<br /> Yeah we got something in common, but your boat looks like it is a whole lot lighter than mine. My boat is not fast, on a good day it has hit 42-45. I thought it should do a bit better. Running a 13 3/8 X 17 aluminum prop. What about you?

You have a 70 horse? My hull weight was 400lbs pre-center console, plywood flooring and, of course, outboard. Couldn't tell you how fast it goes, but I'd guess in the 30 mph range WOT (fast enough for bugs to stick to your teeth if you smile while running). I've got a 13.25 x 17 stainless prop that's cupped for better hole shot. Aluminum gets eaten up in the shallow flats down here (every shallow takeoff you get smaller diameter prop ).

 

[the rebel]

Re: 70 horse Johnson cooling system modification service bulletin

Originally posted by Mid-size Johnson:<br />

Originally posted by Big White Johnson:<br /> Yeah we got something in common, but your boat looks like it is a whole lot lighter than mine. My boat is not fast, on a good day it has hit 42-45. I thought it should do a bit better. Running a 13 3/8 X 17 aluminum prop. What about you?

You have a 70 horse? My hull weight was 400lbs pre-center console, plywood flooring and, of course, outboard. Couldn't tell you how fast it goes, but I'd guess in the 30 mph range WOT (fast enough for bugs to stick to your teeth if you smile while running). I've got a 13.25 x 17 stainless prop that's cupped for better hole shot. Aluminum gets eaten up in the shallow flats down here (every shallow takeoff you get smaller diameter prop ).

Hah, smaller diameter prop, now that's a good one. You do like the shallow water. I'm not that fond of it yet, i try to keep from plowing up the sandbars as much as possible, it takes a toll on your quipment. Yeah I actually have a 75 on mine(look 2 posts up). 70-75 very little difference between them. So i must be running fairly good to get this MPH out of my rig huh? I was thinking 50 mph would be better. I like to bump through the swamps and marshes, so I idle around a lot with the motor tilted. Still don't have my tach working so I don't exactly know if I have it propped just right. Soon as i do, I'm going for a stainless prop. Still thinking about trim tabs.