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Catalina/Capri 25/250 Sailor's Forums

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Nissan 8 HP Outboard (15")

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JimB517
Past Commodore

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USA
3285 Posts

Initially Posted - 03/04/2003 : 16:56:38

Hi, I am going to use this motor on my dinghy. Does anyone have the service manual for it? I am doing some work on it and I would like to save the $37 from Clymer (or it's available on eBay for $25). If someone could send me the manual I would copy the parts I need and send it back. I don't need the whole book, just the part about a 1998 8 HP.

While I am on the subject, the motor runs great (all day) at low throttle. I bought it used and rebuilt with a 90 day warranty. The first time I took it out (90 days later) it overheats after 5 minutes when you put the dinghy on plane - anything above 3/4 throttle. Then it cools down and starts right up again. The water pump telltale seems fine. Compression is fine. Starts on the first pull. Runs smooth. The motor looks like new. The paint has come off around parts of the head gasket but there does not seem to be a leak. We used it about 6 months on our cruise and just kept it slow with no problems. Then we bought a new Mercury 5 HP and put this one in the bilge. The Mercury never overheated or failed us in any way the rest of the year. Ran a lot rougher than the Nissan 2 cylinder.

By the way, we checked really carefully and the water intake was still underwater even when the dinghy was on plane.

I dropped the lower end this weekend and removed the water pump. The impeller is fine. Split open to remove the impeller, the water pump itself shows a little rust along one side between the upper and lower halves. Very minor rust spot, about 1/8 inch long (I could post a photo). I think it maybe is a water leak into the lower end? The gear oil looked like coffee with milk mixed in - along with about 1 tablespoon little bit of gray and white foam (the motor has not been run in 1.5 years).

I would think that if there was a serious water leak into the lower end there would have been all kinds of water in the oil, or could this leak go into the exhaust?

Any other ideas as to what could be causing the overheating?

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/04/2003 : 19:57:10

JimB517,

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>... it overheats after 5 minutes when ... above 3/4 throttle. Then it cools down and starts right up again. The water pump telltale seems fine. Compression is fine. Starts on the first pull. Runs smooth. ... The paint has come off around parts of the head gasket but there does not seem to be a leak. <hr height=1 noshade id=quote></BLOCKQUOTE id=quote>Paint peeling at the cylinder head is frequently a sign of overheating due to lack of cooling water circulation. I'd suggest pulling the head to check for clogged cooling passages. Compression isn't going to stay fine if the motor keeps locking up!

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>I think it maybe is a water leak into the lower end? The gear oil looked like coffee with milk mixed in - along with about 1 tablespoon little bit of gray and white foam ...<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>Milky looking gear oil is a classic sign of water intrusion. Used gear oil should look almost like new, or slightly dark grey, motor oil. Also, any metalic glitter, no matter how finely ground, is another bad sign. I'd suggest having the lower unit pressure tested. That may lead to replacing gaskets and seals. If it's open for that, I'd inspect the bearings and gear teeth contact surfaces with a magnifying glass or pocket microscope.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Does anyone have the service manual for it? ... I would like to save the $37 from Clymer ...<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>It's been my experience that a Clymer (or similar after market) manual isn't worth pursuing. When I get my hands on a new (used) motor, I try to get a copy of the factory service manual -- the one the dealership technicians use. But that's just me.

Good luck! I hope there's an inexpensive explaination for each of your motor's problems.<img src=icon_smile.gif border=0 align=middle>

-- Leon Sisson

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 03/04/2003 : 22:10:16

I'd look for (1) a thermostat that won't open all the way, which might not cause a problem until you throttle way up, and (2) a blockage in a cooling channels possibly for just one of your two (I assume) cylinders. Either way, you can be getting water from the pisser but not enough or in all the right places in the block.

Some gear oil is milky brand new, but the foam is a strong indication of water mixing in the oil. Change the oil and the gaskets on the oil plugs. If it happens again, you may need to replace the prop shaft seal.

Did you get that waranty from a dealer? If so, and you couldn't use it for the entire period, I would think he might give you some consideration...

Good luck,

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 03/05/2003 : 00:41:25

I pulled the head tonight. 2 of the head bolts sheared off leaving studs in the cylinder. I don't know how to extract these. I have them soaking in penetrating oil, perhaps I can turn them out with vice grips. Although I doubt it - several of the head bolts were very rusted and frozen in place. These two were the worst. One is at the very bottom in the worst possible place.

The thermostat looks bad, it is quite rusted and looks frozen. I don't know how to remove it. I can't see anything holding it in, is it just glued in place ?

The cooling passages have some scale, but are open. The head and cylinder surface are caked with parts of the old head gasket but look serviceable if I could get them clean again.

Edited by - on

jm
Captain

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Canada
290 Posts

Response Posted - 03/05/2003 : 09:58:08

Jim - re: headbolts. Just use an undersize highspeed metal bit to drill out as much of the old bolt as you can without touching the threaded wall. (drill press if you have one) If you can get it thin enough, you can sometimes backout the remaining outer portion of the bolt. If not, take a tap and try to crease it until it lets go. Otherwise, I'd take the head down to your local auto machine shop, let them give it a go, and failing that they can re-thread it for a
new oversize head bolt.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.