2003 Maxum 2100SC Riser Gaskets

[Rwhite923]

Question, which gasket should I get for this boat? The motor is a 5.0 Mercruiser with the Thunderbold ignition, and alpha 1 gen 2 drive. The boat originally came with the pinhole gaskets (https://defender.com/en_us/sierra-me...80153138713961)

However, Google Gemini keeps telling me to put the open hole version (https://defender.com/en_us/sierra-me...80153138713961).

I was wondering what you all think?

Just a heads up, I'm pretty new to boating - so have questions. For my 5.0 Mercruiser, I changed the impeller on the Alpha1 Gen2 drive, then changed out the old flappers. After that I changed out the riser gaskets with these. While in there I checked to make sure everything is clear from rust and build up, all was good - this is a fresh water only boat. Later I went in and replaced the thermostat, checking the tubes on housing for any blockage - all was good. I've connected the boat to the hose from my house, and at peak running temp I'm at about 190 F for the engine, and about 210 for the top of the risers (using a infrared gun to measure). All that said, do you think it's a water flow issue from my house, or could it be something else?

[shrew]

Take a picture of the manifold and riser.

Do you have dry exhaust?

You wouldn't normally just replace the gasket and re-install the risers and elbows.

A garden hose should be enough to hold temps at idle.

[Rwhite923]

Originally Posted by shrew

Take a picture of the manifold and riser.

Do you have dry exhaust?

You wouldn't normally just replace the gasket and re-install the risers and elbows.

A garden hose should be enough to hold temps at idle.

Here's the images of the riser, I wasn't able to get pics of the manifold yet.

[Rwhite923]

Originally Posted by Rwhite923

Here's the images of the riser, I wasn't able to get pics of the manifold yet.

Here they are

[shrew]

Those are definitely dry joint. I'm not sure whether you're supposed to be using the restricted gasket or the open gasket.

What temp. thermostat did you install? It should be opening between 140 -160F.

[mmwjr]

Is the 190 F of the engine gauge or IR reading? If IR what part of the engine did you take the reading? Is the engine closed cooled? 210 F on the riser is way too hot unless you have catalytic converters which I don’t think the 5.0 ever came with. If closed cooling are the exhaust manifolds also part of the system or are they open/raw water cooled?

[Rwhite923]

I installed a 160 degree thermostat, same one that was there before.

[Rwhite923]

190 on the gauge, I pointed at the the IR at the thermostat housing and it was around 170 there. The whole system is raw water cooled

[Rwhite923]

There was no corrosion inside where the exhaust is, and very small amounts of corrosion else where. Basically none at all

[mmwjr]

Ok 170 at the thermostat housing is good but 210 on the top of the risers is not. Mine are typically around 120. Note 210 F for an open system is basically boiling.

[Rwhite923]

Originally Posted by Rwhite923

Here they are

Update. boat ran good under load and in the lake. Temps were a reasonable 160 to 175 on the gauge on the thermostat housing. Risers were around 130 - 160 throughout the 1.5 hours we were out.