55 Evinrude 7.5hp Fleetwin tune up

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
My fleetwin blew a head gasket so i think this is a good time to go through it. I checked the impeller and it looked new and was flexible so im just going to leave it. should I take the exhaust port cover off and decarb it? do they still make gaskets for that or would i have to make one? what kind of gear oil should i put in the lower unit?
 

nwcove

Admiral
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May 16, 2011
Messages
6,293
Re: 55 Evinrude 7.5hp Fleetwin tune up

welcome to iboats 14 ftr.

make sure to lap the head to make it flat before reinstalling the head gasket, and make sure to use the proper torque sequence and specs.

i would personally replace the impeller unless you know for sure how old it is.....cheap insurance! as far as the gear oil goes, i use automotive 90wt oil, but marine 90wt is better as it deals with water intrusion better. make sure to get new gaskets for the drain and fill plugs also.
i wouldnt remove the exhaust cover to decarb it, just add some seafoam to your fuel and it will do the job.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 55 Evinrude 7.5hp Fleetwin tune up

I agree with above, if Im going to pull the powerhead, put a new base gasket in, etc.... a new impeller is going in for sure.

Torque for the head bolts is 60 to 84 inch/lbs OR 5 to 7 ft/lbs if you do not have an inch/lbs torque wrench.

Surfacing.jpg
TorqueSequence.jpg
 

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
Re: 55 Evinrude 7.5hp Fleetwin tune up

I got the motor from my grandpa, who says he might have had something done to it. The coils and points look new too so my guess would be he did. when i lap the head should i do the tops of the cylinders too or is the head good enough? if i repalce the impeller do i need to put sealant on the surfaces of the housing or can i just leave it i noticed theres no gasket. whats the right starting point for the high and low needles they got messed up when i took the cowl off?

Thanks for your help
 

1946Zephyr

Vice Admiral
Joined
Oct 21, 2008
Messages
5,556
Re: 55 Evinrude 7.5hp Fleetwin tune up

Head gaskets generally go on dry. You just need to clean the surfaces really good. Nice old motor. I have a '54 and a '55, myself. Keep it tuned right and it'll last you for years.
 

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
Re: 55 Evinrude 7.5hp Fleetwin tune up

I got the motor from my grandpa, who says he might have had something done to it. The coils and points look new too so my guess would be he did. when i lap the head should i do the tops of the cylinders too or is the head good enough? if i repalce the impeller do i need to put sealant on the surfaces of the housing or can i just leave it i noticed theres no gasket. whats the right starting point for the high and low needles they got messed up when i took the cowl off?

Thanks for your help

just lap the head. use a piece of thick glass for your flat surface, and a piece of 400grit sandpaper. figure 8 motion. you will see the low spots if there are any in short order. be sure to use gloves/etc in case the glass breaks. if you havent read the "top secret file" at the beginning of this forum, you should have a look....tons of good reference material.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 55 Evinrude 7.5hp Fleetwin tune up

Put Gasket Sealing Compound on the SS bolts for the impeller housing. Nothing needed on the housing itself. I put 3M 847 beneath the impeller plate to ensure there is no air leaks, but if you dont have any dont worry about it.

Do grease the DS splines, and ensure the seal is in good condition. I usually replace the washer and o ring, they are cheap insurance.

The powerhead mating surface is usually fine, I just dress the heads, and clean the surfaces well. Modern head gaskets go on dry, and have a shiny surface.

Starting settings for the needles are 1.5 turns out from lightly seated for the low, and 3/4 for the high
 

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
Re: 55 Evinrude 7.5hp Fleetwin tune up

When i pulled the head there was water in the bottom cylinder but no rust. Some went down the ports is there anything i need to do or will it just get blown out when i start the motor?
 

TN-25

Chief Petty Officer
Joined
May 27, 2008
Messages
607
Re: 55 Evinrude 7.5hp Fleetwin tune up

I just found this thread. Water in the lower cylinder is a concern. Given that it is a 7.5, there apparently is a weakness in the exhaust bypass cover in which pinholes can develop. This will allow water to squirt into the lower cylinder which can lead to destruction of the motor. This information I am simply repeating from member 1946Zephyr.

Another caveat for these motors is the carbon seal at the base of the powerhead. If it goes bad, water will get into your motor and destroy it. To check it you need to remove the powerhead (it needs to come off to replace the impeller anyway; sounds like a wise investment in the long term). Powerhead removal on these engines is pretty simple as far as that goes since there are only 7 bolts that hold it on. Throttle lever will need to be disconnected, plus carb & fuel lines. It really shouldn't be too big a deal unless everything is seized. Quality tools help.
 

1946Zephyr

Vice Admiral
Joined
Oct 21, 2008
Messages
5,556
Re: 55 Evinrude 7.5hp Fleetwin tune up

Yes, I made several of these inner exhaust cover plates, because I have experienced two of these motors, getting water in the lower cylinder. The most recent one was stuck, but luckily I got it freed up and running. The pin holes in the plate are usually the culprit. If you need a plate, let me know. Mine are made from stainless.
 

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
Re: 55 Evinrude 7.5hp Fleetwin tune up

Ok i thought it was the bad head gasket that caused it but maybe i should put one of those plates in. what is all involved with that right now i have the powerhead off and the cylinder head at the machine shop?
 

merkdawg

Petty Officer 2nd Class
Joined
Feb 26, 2011
Messages
121
Re: 55 Evinrude 7.5hp Fleetwin tune up

The exhaust bypass is on the right side of the motor. It is the plate that your sparkplug bracket is bolted to. Take that off and there is another plate behind that.
 

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
Re: 55 Evinrude 7.5hp Fleetwin tune up

Can i reuse the gasket on the cover or do i need to get a new one? do they even still make them?
 

nwcove

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6,293
Re: 55 Evinrude 7.5hp Fleetwin tune up

you can probably find a new gasket, but its just as easy to go down to your local uap/napa etc, and get a piece of gasket material and make your own for just a few bucks and less than an hours work. ( you can make most of the gaskets , just not the head gasket)

marineengine shows the cover gasket as omc part # 202580, and the head gasket as omc# 203034.

the cover gasket doesnt appear to be available as a sierra part, but the headgasket is listed as part # 18-2952
 

14 ftr

Cadet
Joined
Oct 21, 2012
Messages
13
Re: 55 Evinrude 7.5hp Fleetwin tune up

Can i reuse the gasket on the cover or do i need to get a new one? do they even still make them?
 
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