Is this thru hull exhaust too low on the transom?? Check the pic

[dnsellers]

This was a custom job done on a boat I am thinking about buying. On all the other diagrams for fitting custom thru hull exhaust systems, it always seemed they suggested being at LEAST a few inches above the outdrive. What do you guys think..will this be a problem??

 

[dnsellers]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

I figured that wouldnt work...any sggestion on posting this pic?

Ahhh...there we go.

 

[Bt Doctur]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

maybe the reason being the exaust risers did not have enough height.

 

[dnsellers]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

But is this going to cause any problems?? I figure once up on a plane, the area of the exhaust tips will be out of the water...but what about @ idle?? Even worse, how about in revese. I understand that normally exhaust is routed out underwater thru the outdrive, but that is also with the force of all 8 cylenders exhaust gases being forced out of one hole. Plus it gets routed upwards, not straight inwards...any thoughts?

 

[newport dave]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

How long have they been running it like that? That is a disaster waiting to happen.<br /><br />Dave

 

[Don S]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

The big thing is how it's plumbed inside the boat, not necessarily the outside.<br />As long as the engine is idling, no water is going to back up the exhaust, are there any exhaust shutters inside the thru-hull?

 

[bigbrownbuku]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

i would install flappers and check the minimum recommended riser/waterline height. i believe its around 14 inches.

 

[mercrewser]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

I'd be more concerned about the thru hulls being perfectly sealed so that the plywood transom isnt compromised with water.

 

[Richard Petersen]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Mercruiser has a field installed dual exhaust kit to have a boat look just like yours. Check with Mercruiser on Monday. Have them send you the field instruction pak so you can see if this boat meets the water cooling pipeing to the engine and fully loaded boat water level to the top of the risers dimension. Get the pak for YOUR engine size. Hopefully they copied from another similar boat and your OK.-----------------------------------------If it looks close to ok. Check it in the water with a 15' length of clear hose from a auto store to get a really accurate measurement of waterlevel to the riser top.If not, haggle for the cost to do it right.

 

[bomar76]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Lot of installs around here like that to help beat the sound laws. A friends' performance marine shop does them all the time.<br />They use an 2 pipe in the boat to bring the tips downs below the water when the boat is at idle of slow speed....keeps the noise down.<br />On plane the tips are out and free flowing.<br />They don't use external rubber flappers, but all that I see do use shutters. The curve and rise of the s pipe is really what does 99.9% of the work.<br />I have never heard of anyone having a problem with them.<br />Additionaly some boats have a low swim deck situation and need to have the tips exit low to clear.

 

[rodbolt]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

funny thing is all I ever saw it do on modern center riser through hub systems is make an aggrevating noise, I have never seen any performance gains on a modern stern drive. I have also seen improper installs cause engine problems that warrenty wont cover.so it leaves the question, why?

 

[f_inscreenname]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Why rodbolt?? Because it sound cool and you can get rid of that big "Y" pipe in the motor compartment. I a lucky enough that my boat came that way and I couldn't pass exhaust gases through the drive if I wanted to. <br />As long as you don't tow the boat in reverse I do not think you will get water back up through the exhaust. The pressure from the exhaust when the motor is running should keep any water out when backing up. I would still like to see under the motor cove before I made a finale judgment on the deal.

 

[bomar76]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Why?<br />Because not all of us are into the same kind of boating as the rest.<br />Some of us actually enjoy the performance aspect of boating, and anyone that doen't think the stock y pipe and thru hub exhaust set up doesn't restrict the exhaust of any high performance is delusional.<br />Does it really help on a stock SBC? No<br />Does it help on any BBC? Yes<br /><br />Again, not all of us are piddling around in 1960's trihulls with 4 bangers.

 

[Richard Petersen]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Also, you do get rid of that big hose one day sinking the boat. Some last forever.

 

[rodbolt]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

what big hose sinking the boat?<br /> and yes I have seen thru-transoms that on a rapid shutdown will ingest water. took three times before I could convince a dofus buddy of mine to add flappers.<br /> on some big blocks it helps but only if power goes over 330 hp or so. if you GPS it or dyno it you will find most of it is just a noise increase. sounds cool maybe but I dont think its worth the money.<br /> I dont design them I just fix em. if that is what the customer wants I will install it. but when he complains about the cost and the fact it still only goes 52 MPH all I can say is oh well

 

[dnsellers]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Thanks for all the info. This particular job was dont when the original 135 HP 3.0L was swapped w/ a 5.0L V8. NO, the boat isn't rated for it but ohh well. Inside the engine compartment you can suspect there is next to no room left. I am thinking it was done this way because of clearence issuees, but as lonf as no water is getting back up in there...wonderful.

 

[Don S]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Derek, perhaps you could take a picture of how the inside of the exhaust is plumbed. From the sounds of the replies, many think that the thru the transom exhaust tubes are coming right off the end of the exhaust manifold instead of a drop down from the risers.

 

[dnsellers]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Sure thing...I'll se if I can get a few more pics of the inside.

 

[Richard Petersen]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Rodbolt, we had a near miss. Guy leaves his boat at his slip for 1-3 weeks at a time. Lucky he also puts the hoist slings loosely under it. Full of water and tight slings, exhaust hose.-----------------------You are right about stock engines sound cool, but do the same GPS.

 

[Richard Petersen]

Re: Is this thru hull exhaust too low on the transom?? Check the pic

Derek, Is your boat about 17' to 18.5' ? If so, TOMMAYS will fill you in about what to expect in the summer with that engine in it's close fitting box.