Aq131d overheating issue

hi guys i have a AQ131D engine and its overheating replaced impeller and am having heat exchanger tested but was wondering about exhaust manifold as i have seen on other posts that peolpe have problems with the number 4 exhaust port on there heads was wondering how this causes a overheating issue . does the water circulate through the exhaust manifold on these motors . sorry if these are stupid questions new to working on these motors thanks in advance

Re: Aq131d overheating issue

A little more information would help. If the temp stays normal when at idle or slow speed and then goes up as your speed increases, then the water connection on the outdrive is suspect. They erode from the inside so it may be difficult to tell but they are considered a routine replacement item. Yes, the rest of your cooling should be inspected and verified as well but the water neck fitting is a common bad actor that isn't allways obvious.

As far as the #4 exhaust port, yes, it's typical for it to become eaten away but it's not a difficult fix for a machine shop and it should not affect engine temp.

Re: Aq131d overheating issue

we were running it on muffs and it was getting hot cant remember last time we were on the lake if it was gettin hot at idle or at speed but we will be testing it out soon and will repost thanks for the info

Re: Aq131d overheating issue

I had an overheating issue on my aq131 as well. I had the issue at #4 exhaust port. I decided to change the cylinder head. While I had it apart I also replaced the heat exchanger core. I also replaced the exhaust manifold.

Answer to your question tho, yes water does circulate through the exhaust manifold. Thats why the #4 exhaust port goes away...I believe its because of valve overlap, it allows a small portion, probably a light mist of water to get into the port and have its way with the metal.

I found a leak at the bushing in my outdrive as well. I went with a thru-hull water pick-up instead of messing with the drive. The way I was able to determine I had a leak at the drive was I put the muffs on and without running the engine I squeezed the muffs and looked for a water leak on the drive. Mine was leaking water at one of the bushings, so for sure it would have sucked air. I fixed that and it still overheated. So like I say I said screw it and went with the thru hull.

What I didnt realize at first, is if the exhaust manifold is corroded inside it will cause a water restriction on the exit side of the water. So if you're putting water into the heat exchanger you have to get it out as well....if the manifold is corroded it wont let the water out fast enough.

Hope this helps.