FWC cooling questions on mag mpi 7.4 380 hp horizons

[370Dancer]

When I bought my 370 Dancer, it had just had the 3rd set of engines put in. This time, the exhaust system was changed to hydrolift cannisters.

This week, I started to change the manifolds/risers and ran across a couple of things that made me go hmmmmm.

1. Never really looked at it closely, but today realized that I have a FWC half system installed. The manifolds, spacers, and risers are all raw water cooled. I've read that half systems are usually only needed for high performance motors. Would the 380hp engine fall in that category? Or, was the installer just being lazy? I've always plumbed full systems on my other boats.

2. The manifold to spacer (6"), and spacer to elbow gaskets are both full gaskets. All 4 sides of the water jacket are open. I have read that if you use spacers, that the gasket between the spacer and the elbow should be a restrictor gasket, where 2 of the water jacket openings are small holes. Or, are those just used on full raw water systems?

Both engines run around 165-170 degrees Stbd is slightly cooler as it has the cockpit heater plumbing on it.

Opinions?

 

[Sea Gull]

I owned the exact boat. 1998 370 DA with 380 hp MAG MPI Horizon engines. During the 4 years I owned the boat I had 3 sets of engine replacements. The boat was originally equipped with the half cooling system that you describe. Concurrent with the second replacement, they installed the modified exhaust system. While I owned the boat they did not add closed cooling to the manifolds and risers. I cannot remember if they increased the height of the spacer and can't comment on the gasketing issue.

I traded the boat back to the dealer when they could not promise me that they knew how and why the engines kept ingesting water and the warranties were expiring. I can tell you that I have since been in contact with the guy who bought the boat and he has had ongoing problems as well.

I think full closed cooling is a smart approach. How long have you owned the boat? Is there any sign of water ingestion?

 

[370Dancer]

I haven't had any ingestion issues. I've owned the boat since November of 2003.

The folklore goes in a couple of directions. One, is that with the old exhaust, it was barely above the waterline. People tended to congregate in the spacious cockpit, lowering the waterline to the point of backflow. Similarily coming off plane, if you let the sternwave come over the platform, chances are you let some water in.
Another one was due to the ECU timing variations at idle, it could let a bit in.
4 years on the manifolds and risers. The risers were definitely caked up, and one had a pinhole in it, causing steam in the exhaust. I'll post some pics later today.

 

[Bridog]

When I bought my 370 Dancer, it had just had the 3rd set of engines put in. This time, the exhaust system was changed to hydrolift cannisters.

Holy crow between you and Sea Gull thats 12 engines replaced due to water ingestion. Was it under warranty? Did SR/Merc make it right? Good luck.

 

[370Dancer]

Mine were all under extended warranty, and a bit of wrangling with Merc and Sea Ray (before me).