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Fman

409/450 owners please read this

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Fman

I just returned from Lake Powell on my friends MB with the 409. At 150 hours he had a fitting come off the thermostat housing, it is a plastic elbow that seems to loosen up over time and actually falls out of the block. He replaced it with another one, at 334 hours while on his boat it started to loosen up again and begin leaking. We pulled it out and wrapped teflon tape around it and used a hose clamp to secure it to the block. We are trying to find the attached fitting in a brass version to help eliminate this problem. His prior boat had a PCM block and they used brass fittings for these connections. I am also wondering if the 450 has the same plastic fitting? And has anyone else with a 409 experienced this problem? I have 115 hours on my engine with no issues, but his did not come loose and fall off until approx 150 hours. I am planning on just replacing it with a brass fitting if one is available. If anyone knows of a vendor that has this fitting in a brass version please send the link, it can even be any 90 degree elbow just needs to match up thread and hose size.

20150911_112702-1-2_zpspegftzm4.jpg

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robbennett

It should be NPT thread. Try your local hardware store.

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Bawshogg

I'd be willing to bet those threads are not just "going bad" . They are most likely failing due to heat.

Indmar had an update in the cooling system hose routing and a subsequent reprogram to the ecm also. Has this been done on that MB yet?

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Woodski

I have seen those fittings fail in more than just the 409/450 application. Stainless Marine uses aluminum fittings on their aluminum exhaust manifolds so that is an option. A good hardware or plumbing supply house should have a brass option.

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shawndoggy

Yeah a friend here has had them pop out of the exhaust manifolds on a 2012 monsoon 350.

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Fman

Ok, so we are not crazy. His engine runs at about 175 all day long, when he shuts it off it will go up to 190 but then cool down immediately when it starts up again. Interesting because my 409 seems to run at 160 all day, and will heat up to about 175 when I shut off the engine, not sure if he has a different thermostat or his gauge is not reading properly? Why is Indmar using a plastic fitting for this? I sent email today to the supplier of this part to see if we can get a couple brass ones from them, I will also check the local hardware store. As I mentioned earlier, his older MB had a 350 with PCM engine and they were all brass fittings, seems like Indmar cheaped out on this and went with these plastic junkers.

Baws, I will ask him about the ecm update, his boat was built in 2013 but was one of the first 2014 models that rolled out of the MB plant.

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Fman

I am going to have to do some research on this, according to Bakes they say not to replace it with anything other than the nylon elbow??? I am assuming this is the same fitting coming off the thermostat housing.

https://www.bakesonline.com/detail.aspx?ID=885

Edited by Fman

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shawndoggy

His engine runs at about 175 all day long, when he shuts it off it will go up to 190 but then cool down immediately when it starts up again. Interesting because my 409 seems to run at 160 all day, and will heat up to about 175 when I shut off the engine, not sure if he has a different thermostat or his gauge is not reading properly?

I wonder if that's just the gauges MB uses? My PCM equipped EX343 also ran 175. I just ignore the numbers and look for "normal," and "not normal". It did 175 all the time since brand new. Who knows what the "actual" temperature was?

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Andrew63

I am going to have to do some research on this, according to Bakes they say not to replace it with anything other than the nylon elbow??? I am assuming this is the same fitting coming off the thermostat housing.

https://www.bakesonline.com/detail.aspx?ID=885

Yet there is a brass fitting from the factory, fitted in the same manifold (350 Monsoon CAT) between the 02 sensors.

Fitting is still carrying water & alloy will not change in the same casting.....

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Andrew63

Sent off an enquiry to Lary @ Indmar about these nylon elbows.

His response below

You could use brass fittings to replace any of those fittings in the manifold. Brass and nylon fittings are used because they typically do not lead to electrolysis. If you can find the appropriate brass fittings it is perfectly acceptable to use them.

We used the brass fitting at the top of the manifold because the manifold sometimes gets warmer at that point and the nylon fittings did not like the extra heat. The 90 degree and straight fittings in the lower positions typically saw much cooler water and did not justify the extra cost of using brass fittings but if they would have required brass fittings, they would not have caused any issues.

Larry Engelbert

Indmar Marine Engines

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Dodger40

First of all, shame on the engine suppliers! A few bucks saved has caused an awful lot of problems. Second where do we find the brass replacement.

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shawndoggy

i just did a bit of googling and I can't find any brass replacements that match the sizes indmar uses. All step up or step down between the threaded NPT male end and the barbed end. They must be out there but not at the usual (easy) sources...

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oldjeep

i just did a bit of googling and I can't find any brass replacements that match the sizes indmar uses. All step up or step down between the threaded NPT male end and the barbed end. They must be out there but not at the usual (easy) sources...

Try looking for a 90 with male/female threads and then a hose to female fitting.

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shawndoggy

Try looking for a 90 with male/female threads and then a hose to female fitting.

yeah that's the thing.... you could do a couple of them with reducer bushings too. But getting a one piece drop in bit not so easy.

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Fman

I need to find out if it's a 1" npt x 1" or 3/4" npt x 1". My friend is out of town until friday, he said he would take measurements when he gets home.

If I can find the correct part I am definitely swapping mine out.

This looks like it could work

http://www.suremarineservice.com/FIT-086.aspx

Edited by Fman

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SmoothWaterMan

Hey guys, the nylon fittings were spec'd before a time when listing a boat became prevalent. One of the reasons Indmar came out with a revised water flow setup was to address this very issue. Water will take the path of least resistance, and when it was listed the "uphill" exhaust manifold was quite often starving for water. The revised water flow kit addressed this and provided good flow to both sides.

That said, the thermostat in the RWC engines are 160 degree, and I don't expect you should see a 15 degree higher temp when running. 10 degrees maybe, but in the northeast we never see anything greater than 165, unless something is restricting the water or the impeller isn't pushing.

The engines that are FWC can often run at a higher temp, but with less fluctuation.

Peter

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robbennett

In Georgia I never have even seen my engine as high as 165. That's even running in 100+ degree heat and 90+ water temps.

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Andrew63

I need to find out if it's a 1" npt x 1" or 3/4" npt x 1". My friend is out of town until friday, he said he would take measurements when he gets home.

If I can find the correct part I am definitely swapping mine out.

This looks like it could work

http://www.suremarineservice.com/FIT-086.aspx

Yep. 3/4" NPT to 1" barb.

These are the dims. quoted for the Gaan replacement below

https://www.bakesonline.com/detail.aspx?ID=885

Showing 12 in stock at the link in the post #15 above.

Wonder how long B4 the supplier wonders why his stock movement went through the roof.

Mine you a combination or FF elbows, barb & Nipple will give you more clearence away froom the manifold for the hose.

May find once the one peice elbow is fitted there is bugger all roof for the wall thickness of the hose & clamp to fit over the barb

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Fman

Hey guys, the nylon fittings were spec'd before a time when listing a boat became prevalent. One of the reasons Indmar came out with a revised water flow setup was to address this very issue. Water will take the path of least resistance, and when it was listed the "uphill" exhaust manifold was quite often starving for water. The revised water flow kit addressed this and provided good flow to both sides.

That said, the thermostat in the RWC engines are 160 degree, and I don't expect you should see a 15 degree higher temp when running. 10 degrees maybe, but in the northeast we never see anything greater than 165, unless something is restricting the water or the impeller isn't pushing.

The engines that are FWC can often run at a higher temp, but with less fluctuation.

Peter

Do you think his engine is just running too hot causing this fitting to fail? Have you ever seen this problem happen before on the 350/409/450? Like I mentioned it was showing 175 on his temp gauge, spiking up to 190 when shut off. Assuming the temp gauge is dead accurate, it's a 2014 MB.

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Fman

Yep. 3/4" NPT to 1" barb.

These are the dims. quoted for the Gaan replacement below

https://www.bakesonline.com/detail.aspx?ID=885

Showing 12 in stock at the link in the post #15 above.

Wonder how long B4 the supplier wonders why his stock movement went through the roof.

Mine you a combination or FF elbows, barb & Nipple will give you more clearence away froom the manifold for the hose.

May find once the one peice elbow is fitted there is bugger all roof for the wall thickness of the hose & clamp to fit over the barb

I would measure actual fitting before I ordered anything, would not trust that website on dimensions.

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robbennett

Keep in mind NPT is a little funny with it's measurements. The outside diameter will measure just over an inch. 1.05 to be exact.

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Andrew63

I would measure actual fitting before I ordered anything, would not trust that website on dimensions.

Whan my Nylon elbows went last season, I purchsed the Bakes Gaan elbows & they were a direct replacement so the site dims & thread are good.

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Andrew63

Sorry guys, the OEM replacement in the EXT manifold of a 350 Monsoon is not a 3/4" NPT.

It is a 1/2" x 14 TPI NPT x 1" barb as in this link

https://www.bakesonline.com/detail.aspx?ID=2514

How do I know?

I purchased a tap to clean out the corrosion in the threads B4 fitting the new Nylon elbows & checked the Tap.

1/2" x 14 TPI NPT

For those wishing to measure the existing fitting

1/2" x 14 TPI NPT with an OD 0.840"

3/4" may be in some other models which measures OD 1.050"

In case you wish to check a few more dims.

http://machiningproducts.com/html/NPT-Thread-Dimensions.html

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Fman

Andrew the part I am referring to is NOT on exhaust manifold, its on the lower thermostat housing. Without checking my engine and according to Indmar the upper elbows on exhaust manifolds are brass, its the lower fittings that are nylon.

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Fman

Just got confirmation the part size is 1" NPT x 1 1/4" hose fitting.

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