thru hull exhaust conversion

Ok i have an 85 stringer 400 series and was wondering if it would hurt anything or cause any problems if i converted it to thru-hull exhaust the reason for this is omc parts are hard to find and expensive i have a mercruiser manifold that came on a motor i bought for some other parts and my omc manifold does not completely cover the number 2 intake or exhaust ports but the mercruiser will dont know why this is my original head which could be from another engine and the new 87 model mercruiser donor heads are identicalso i am thinking of using the mercruiser head and intake which the riser is longer than mine so would change to thru hull if possible thank you in advance for any and all help

Re: thru hull exhaust conversion

I don't see how your selectrim could work. the engine tips to trim the drive.
It also may not be legal (it isn't where I boat unless the boat is pre 1960).
also.... it would sound horrid.

Re: thru hull exhaust conversion

Well for now my selectrim doesnt work sound dont bother rather listen to horid exhaust than a major leak popping in the boat and im sure i could get enough flex to work with the selectrim and i dont know exactly what the laws are here or what would be different other than the fact that mine was thru prop but both my cousins supra and my brothers nautique are both thru hull

Re: thru hull exhaust conversion

vick 84 said:

Well for now my selectrim doesnt work sound dont bother rather listen to horid exhaust than a major leak popping in the boat and im sure i could get enough flex to work with the selectrim and i dont know exactly what the laws are here or what would be different other than the fact that mine was thru prop but both my cousins supra and my brothers nautique are both thru hull

Click to expand...

Ayuh,.... Whatever trips yer trigger,....

If you can make it work, you'll spend the rest of the boat's life, tryin' to quiet it down....

'cause it's gonna sound Worse than a lawnmower, without a muffler...

Re: thru hull exhaust conversion

Well let me throw another issue i am having when under it tops out wot at around 3500 rpms and about 25 mph dont know the ratio in the out drive but it is i believe 13 3/4" x 15" prop boat is 19'6" galaxy bow rider selectrim isnt working but it is getting on plane for the most part i have converted to the ect ignition for the donor motor timing is very close read somewhere that it could be a dirty/plugged up flame arrestor causing it to run rich does this sound right or should i look else where im going to try chanhing the carb jets to the ones off the donor motor since it is from here in texas and the boat came from new york i dont know if it was rejetted when it made this voyage as to im at least the third owner since any help with this would be great

Re: thru hull exhaust conversion

With a little common sense you should be able to route the exhaust through the hull AND run small mufflers like a Flow Master. We have done this before and even welded a tube in the exhaust pipes for the water pump returns to flow out of the exhaust.