95 omc 5.8 runs cool without thermostat but eventually overheats with the thermostat

[VancouverBoat]

Thanks guys. Here is video with clear hose between incoming water and thermo housing. It shows increase from idle to 3200. Does not appear to be bubbles in general but there is a very brief period of bubbles with a quick increase in rpm but it returns to no bubbles quickly as it reaches 3200. Is that normal?. It is not under load here as I could not get assistant to film out on the water yet. I would think that the incoming raw water should not really be affected by load since it would just be the speed of the rpm that would determine the flow. No? https://photos.app.goo.gl/1pKTJZ5ZGxDddHE76
https://photos.app.goo.gl/1ZXNRD9Fuv9Qr7Gb7

Lou there is no water in cylinder, rust on electrodes or water in the oil. Compression is good.

 

[VancouverBoat]

PS, can you inspect/replace the hose between pivot housing and transom plate without removing the drive? Perhaps by raising the leg fully and turning drive all the way to starboard?

 

[kenny nunez]

If the boat is on a trailer the hose can be replaced.

 

[VancouverBoat]

OK, I took the boat out o the water today with clear tube from inlet hose to thermostat house and and I did see significant bubble froth develop in the tube when I get up past 3000 rpm in the water. As you said before, there must be air getting in at high speeds perhaps in the inlet hose between transom plate and upper drive. It did not do that before. Be nice to have an easy fix for once... I cannot find anywhere that it shows how to replace this tube on a trailer without having to take it all off including bellows. Any links you can provide would be appreciated.

 

[kenny nunez]

How about finally getting it over with and plumb the intake through the bottom. It may be possible that the plastic nipple in the pivot housing is cracked and you may have a very hard time replacing it or have a hard time finding one.
Trying to repair the drive is a lot harder if you have no previous experience with this sort of work.
This will get you back in the water within a few hours.
This is what you need from GROCO who makes the fittings. This is their part #s. STH1000W through hull , or STH1000W intake strainer, either one will work but I prefer strainer version and they are both 1”npt and IBV1000 valve. Three 1”X1” hose barb fittings, one 1” npt “T” fitting to connect the hose from the drive to the through hull fitting. This way water circulates through the drive to keep the oil cool from the exhaust. And you will still be able to run the engine on a flush out on the drive. I believe the incoming hose to the raw water pump is 1” ID.
I am sure that the marina will have these in stock. All you need is a 1/14” hole saw and some Stainless #8 or #10 machine screws with nuts and washers plus sealer. If you have any any further questions call me @ 504 427 6905

 

[VancouverBoat]

Kenny thanks so much. Yes, I will get it over with and try that. With the 2 sources of suction (drive and through-hull) connected, what stops air from getting into the flow like before from the drive inlet side?

 

[kenny nunez]

That should not be an issue, by using the strainer through hull fitting there will be a ram effect.
You will also need a 1”npt close or 2” nipple to connect the “T” fitting to the top of the valve. I figure that you already have clamps and hose.
You will need to drill 2 additional holes to keep the strainer from turning and probably #8 size should be enough with nuts and washers.

 

[VancouverBoat]

That should not be an issue, by using the strainer through hull fitting there will be a ram effect.
You will also need a 1”npt close or 2” nipple to connect the “T” fitting to the top of the valve. I figure that you already have clamps and hose.
You will need to drill 2 additional holes to keep the strainer from turning and probably #8 size should be enough with nuts and washers.

Buckled down and took off drive and lower gearcase. Hose and nipple were good but lower seal was not in great shape. Looks like it melted.

 

[kenny nunez]

Buckled down and took off drive and lower gearcase. Hose and nipple were good but lower seal was not in great shape. Looks like it melted. View attachment 328387

Looks like you found the other main problem. It is really hard to diagnose one problem when there were actually 2. Hopefully the bolts will come out and the mating surface is not eroded away. That area must have really got hot at some point in the past. Let’s hope this is the final solution.