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Discussion Starter · #1 ·
First Is the 1990 Mariner 4HP based on a Yamaha or Mercury?

Can anyone tell me how to start to change the impeller on a 4HP Mariner. Every where I search on the net says buy a book - I want somebody to actually answer the question.
I have split the lower gear box unit from the leg but it will not just pull out so I stopped there for the time being. There is a large hole in the leg and through this I can see a clamp bolt fixing 2 rods. Is this the culprit holding it all in place?
Hope somebody can answer this

Cheers
Mick
 

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I have owned both a Yamaha 4 and a Mariner 4 from that era. Unless there was a model change around that time they appear to be identical. The Yamaha ran on 100:1 mix and the Mariner 50:1.

You are right in your assumption that the rod under that big hole in the leg needs diconnected - the clamp holding the two halves together has one screw which needs slackened.

There is also a tube from the pump to the head. This should pull out of the head as you remove the gearbox.

Same with the drive shaft - except the splines on the head end sometimes stick. Had to destroy the water pump on the Mariner on the first occasion - the spline had stuck and the drive pin on the water pump end pulled through the plastic and thin stainless pump body.

When you have it apart but before you lift the impeller out check the direction the vanes on the pump are curled. Just to be sure you put them back the same way - I usually take a photo of anything like that with my digital. Saves having a wee panic attack due to memory failure later on.

Sure there will be some outboard experts along with more advice soon. I am just the 'bodger'.
 

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Discussion Starter · #3 ·
Take a star for that. First decent answer I'd had, Of course if anyone can add any more tips I'd be grateful.
Cheers
Mick
 

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Take a star for that. First decent answer I'd had, Of course if anyone can add any more tips I'd be grateful.
Cheers
Mick
You are welcome!

The Mariner needed another impeller change and I found the Yamaha impeller fitted. Still got the old Mariner in the garage - though I gave it to a pal when his 8hp aux got nicked.

It had problems with water flow still - but a run in the tank with a solution of Salt-X helped. These little engines seem very prone to salt crystals clogging the narrow cooling galleries.

Being used as an auxilliary did not help much either - only occasional use and not a lot of TLC.

Memory kicked in again - the tube from the pump actually pulls out of the pump when you pull the bottom end off. Just slides into a rubber grommet.

Lining everything thing up for re-assembly is great fun (NOT)
 

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Take a star for that. First decent answer I'd had, Of course if anyone can add any more tips I'd be grateful.
Cheers
Mick
On the linkage clamp you see through the hole on the leg the clamp is a fiddle when you came to reassemble it. It's a 3 pairs of hands type job as stated. Use a dab of superglue on the groove in it to hold it to the rod coming from the powerhead end. Hold it with long nose pliers or forceps till it sets. That will help to hold it in place. While you line everything up from the bottom gearbox end and slide it in place. Once you have the lower rod in the clamp and lightly tightened a good tap with a screwdriver tip will free the clamp from the glue and allow you to slide it about to set the length properly for the engagement of the gears.
 

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Take the spark plug lead off the plug first for safety before you start..

I find it easier to select forward gear before loosening the clamp, makes getting it back in the right place on reassembly easier for me.

Dab of Fairy on the impeller vanes will make it easier to get them in the housing, similarly with the tube into the rubber gromet.

Clean off the mating faces of the housing and pump body, I like to smear on a thin coating of RTV on both faces.

Put the thinnest smear of grease on the splines of the drive shaft to ease them in, not too much or it can hydraulic and it won't seat. If it is being a bit stubborn seating and you went with the forward gear suggestion you can give the prop a bit of a turn it will turn the driveshaft and help align the splines. (Easier than trying to turn the flywheel and jiggle the box in place at the ame time.)
 

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:clap: First class.

Thanks for taking the trouble to produce that video. Sure a lot of folk will find it handy.
 
G

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I have just replaced the water impellor and am having some difficulty mating the drive shaft and the lower unit to the power head. I can't get the lower unit to close the last 2 inches. Any clues most welcome.
 

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The top end of the drive shaft won't be engaging the drive from the power head. i.e. the splines on the shaft have to slide in to the grooves of the drive 'cog'.
To align the shaft turn the prop shaft (easier with the prop on, or clamp a vice grips to the prop shaft, careful not to clamp too tight and damage the shaft) which will turn the drive shaft. Turning the prop shaft slightly, whilst pushing up on the leg should get everything to slide in to place. It's a bit of fiddle, I've done a few now and have just done the same job on my Mariner 4hp.
 
G

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Thanks for the advice. Thought this was the problem. Tried for about 4 hours yesterday to align the drive shaft with the spline without success. Went to the garage today and first time I tried it, slid straight in. All fixed.
 
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