[theeasynine]

Ok I'm trying to keep from vapor locking. I have insulated the fuel line from the filter back to the injector pump I believe since it runs right along the engine. As for keeping the engine compartment cool, has anyone installed a blower to pull in fresh, cooler air? I thought if that was blowing cooler air under the engine and the exhaust blower is taking air from above the engine it should help quite a bit.

Curious to your thoughts.

[DFZ272]

This problem you are having, is it a brand new problem. What I am asking is how many summers have you had the boat and is this something that has ever happened before? Just trying to find out if anything/running conditions has changed. This may sound silly but is it only happening when the weather is hot or does it happen when it is cooler also?
Are there any service bulletins from mercruiser about this problem? I know you have read a few things about this problem in other places in the forums, I assume they have not helped solve your problem?
Happy boating,
Dan

[theeasynine]

We have owned this boat for 2 summers but last summer we only had it out 3 times late when it was cooler. There is a service bulletin and I've done everything short of installing an inline pump. We changed to alcohol free gasoline. If I get up around 40mph+ the engine temp rises to almost 225. It has even happened trying to trailer the boat if it takes awhile you try to throttle a little. But then my brother had it out all day this summer and had no problems. I am getting tired of being towed back to dock.
I am going to go out this weekend hopefully to see if the insulation helps.

[Mariah350]

Originally Posted by theeasynine

Ok I'm trying to keep from vapor locking. I have insulated the fuel line from the filter back to the injector pump I believe since it runs right along the engine. As for keeping the engine compartment cool, has anyone installed a blower to pull in fresh, cooler air? I thought if that was blowing cooler air under the engine and the exhaust blower is taking air from above the engine it should help quite a bit.

Curious to your thoughts.

I'm sorry need more detail on the problem? Vapor Lock is to general.

Thanks

[theeasynine]

Stall issue

[DFZ272]

Patrick, if you can, post the engine serial numbers so I can look up some specific info. 225 deg is WAY HOT. In general temps that hot border on detonation in the combustion chambers. My 7.4, though a carb model engine NEVER gets above 185 deg in the dead of summer. You may have a general cooling system issue and the vapor lock is simply a symptom. Maybe a silly question, but has the impeller in you pump been replaced lately? Are all you cooling system hoses in good shaped and not kinked in any way? Are they ran correctly especially the sea water pump inlet hose? Just me rambling, lol. Your engine temp shouldn't exceed the thermostat specs that many degrees. 7.4's use if I remember right a 160 deg thermostat. The engine also has an overtemp sensor that will shut off you motor, but I don't know the specific temp off the top of my head. Like I said post the serial numbers and we might can look at your problem from a different angle. Don't get discouraged
Happy Boating
Dan

[theeasynine]

Dan, I found a 90 degree elbow hose that is top of the water pump and goes into the block that looks like it crimps a little too much when it's installed. It looks like it could slow down the water flow. As far as I could tell the inlet hose in the outdrive looks okay. I really don't know where the inlet hose goes into the engine. Any help would be appreciated!

[DFZ272]

Patrick check in Mercruiser manual section under the Mercruiser maintenance section of the forum. It should be on the last page of the manuals listed..Service manual 454/502 7.4 & 8.2 liter On this page the manual is broken down into sections. Check out the cooling system section. It has diagrams showing the proper hose routings. There is a difference in the inlet and outlet positions on the raw water pump for fuel injected and non fuel injected engines and if they are wrong it will cause problems. The hose from the outdrive goes to a raw water pump that should be on the lower driver side of the engine. It pumps water to the engine mounted pump for distribution to the block. You will have to look at the manual to see the exact routings.
Hope this helps and let me know what u find.
Happy Boating
Dan

[Hudson River Steve]

Patrick,
Dan is right, 225 degrees is way too hot. You either have a cooling system problem or you may have a lean fuel situation or even a timing problem. I would start by looking for a restriction in the cooling system (pieces of an old impeller stuck in the fuel cooler, scaled/rusted up elbows etc.) or you may have a worn out impeller in the raw water pump. I have even seen the steel impeller on the engine circulating pump corrode away to almost nothing. I have a cooling system diagram for a 1999 7.4 MPI, let me know if your motor injected and I will try to get it to you.
Good luck,
Steve

[theeasynine]

Ok I took it in to get looked at yesterday. I'll let you know what they find.