Just Changed the TPS and IAC valve on a 7.4 Horizon... what a whipping!

[friscoboater]

As many of you know, my Father joined the Sea ray family a few months back with a 2000 340 with twin 7.4 Mag Horizons, and just recently joined the board (texray340). Since it got really cold the port engine did not want to start at all without multiple attempts and advancing the throttle quite a bit. I just thought it was a cold natured beast, and that was normal. Well after doing dome searching I found that the likely culprit after ruling out fuel pressure was the Idle air control valve (IAC). Being that the engine is a V-drive meant that you had to remove the exhaust elbow, or the intake plenum to do so. Well a well know mechanic in our area said it was easier to remove the plenum as the exhaust hoses are like wrestling a python! So that is what we did... we removed the torx bolts and took off the plenum. It is amazing to me how difficult marine manufactures make this stuff. Anyway we cleaned all the throttle body really good, and installed a new IAC valve, and went ahead and replaced the Throttle position sensor (TPS) for good measure.

Once we buttoned everything I hit the switch. The engine stumbled a bit, but then became acquainted with its new parts and ran perfect. Just to make sure, we went back out in the morning and fired her up... flawless!!! So the starboard engine is starting to exhibit the same symptom, so I will change that out too, and make a how too video on how it is done.

 

[Quint4]

I love happy endings.

 

[Escapade]

Great to hear issue solved. That is fantastic that you will be making a video of the IAC change. I do rely on those great YouTube vidoes to learn and solve many mechanical issues we would have normally call the tehnicians in for. I boated for alsmost 30 years w/ big blocks and never had the IAC issue till this year on the 8.2s. So if your one of those guys making the videos many thanks!

 

[The W.A.V.E.]

Frisco, I love your youtube how to's, Cant wait to see this one. Let us know when its up.

 

[Knot It]

I would love to see this how to video also. This spring, I want/need to clean the air intake filter on my 7.4 horizon. I put alittle over 100 hours on her since we got the boat and this has not been done and I dont know when it was done last. They dont look bad, I just want to do it as part of my spring shakedown. The manual says to remove it for cleaning but to do that, I think I will have to either remove the port risers or the plenum. Is that correct or is there an easier way to do this?

 

[jgoedd99]

I came up with a pretty good way to clean my spark arrester/air intake on my 7.4 Mag MPIs. Like you I cannot remove them from the boat because the exhaust elbows are in the way. So what i do is loosen all the bolts on the flame arreester, and i can slide it about an inch or so away from the air intake that it mounts to. I then take an aluminum foil baking pan (you can get them at the grocery store) and kind of work it under the spark arrester so it is completely under it. You will need to bend/reshape the pan to get it completely under. It now acts as a drip pan to catch the carb cleaner that i spray through the flame arrester. You have to stop occasionally and dump out the carb cleaner from the pan, and then put the pan back under and clean some more. If you use the spray wand on the can, you can insert it inside the filter and clean the bottom side of the arrester from the inside out. All in all it works pretty good, and is a lot easier than removing elbows. A couple oil adsorbent pads are nice to keep handy in case you see a spill or the fluid misses the pan.