Repowering ...Need a recommendation on Exhaust manifolds/risers

[donmcfadden]

I have a 1983 Chris Craft Catalina 281 which has 2 chris craft 305 motors in it which I am replacing with new motors (still 305) and transmissions. I had a got a great deal on 2 long blocks. I am changing the exhaust system completely to the mufflers and I am wondering if anyone has any recommendations for exhaust manifolds and risers <br /><br />Since I am changing both motors and I need to replace some old iron ehaust pieces, I figured it doesn't matter which 'design' of exhaust manifolds I use. I am looking for the best combination of Cost/ Life/ and ease of finding replacements. <br /><br />The old engines were raw water cooled and after 20 years of salt water use they were done (probably mostly done after 15 years)- with that life I am not looking to go fresh water cooled on the new motors- unless I am really talked out of it. <br /><br />Anyway any suggestions are welcome- Currently I am leaning towards the mercruiser design since it seems to both be the cheapest and most available, but I am unsure of there life expectancy.

 

[FatBack]

Re: Repowering ...Need a recommendation on Exhaust manifolds/risers

Three inch center risers will work great if they line up with the thru hull exhaust ports. It's the angle of the dangle that's your challenge. Does your 305's take high profile or low profile rocker arm covers? The center riser manifolds are different for each style of cover. Log type are more expensive,but if you have to get your angle right, you may have to use them with inboard risers. It really depends on the angle of the dangle. Good Luck

 

[donmcfadden]

Re: Repowering ...Need a recommendation on Exhaust manifolds/risers

I am not sure on the profile of the rocker arm covers, but I know have plenty of run to worry about lining up with the through hulls. It is a straight inboard and there is about a 5' run from the back end of the engine to the transom. I am gutting all of the metal exhaust pieces (used to y both sides of each engine and convert from 3" to 4" diameter) that were used originally - as well as the transmissions (old were straight direct drives, new have 8 degree down angle) so luckily I won't need to worry about lining up anything till I get to the mufflers. It would probably be a fools frustration to try and re-use the existing ehaust system anyway with the engine now sitting more level and going from log style manifolds to center risers.<br /><br />Is there any difference in reliability in any of the designs? Since I have so much to change I am free to pick the best balance of cost/reliability. My mechanic sells aqua power manifolds/ risers and is, of course, pushing them (in the center riser design), but I am just looking for some opinions on what you would pick if you were in my situation.<br /><br />thanks.

 

[mikeblare]

Re: Repowering ...Need a recommendation on Exhaust manifolds/risers

It would be better to stay with the same design unless you are changing to all new complete motors and exhausts. I just changed over from log to center on my chris craft scorpion w/merc 305 #1 drive. So far I have had to change alternator and steering pump brackets remote starter solenoid mount fuel filter mount. All of these mounted to the exhaust manifolds. Plus as I just found out today I think I am going to have to change the thermostat housing because of the route through the block the log style goes out of the engine into the manifold back into the engine and then out into the riser. The center style just goes out into the manifold and riser and then out not back into the block this use a different style thermo housing. It is a severe pain in the A$%. I hope this helps with your decision.

 

[akriverrat]

Re: Repowering ...Need a recommendation on Exhaust manifolds/risers

kemequipment.com/ sells center riser aluminum manifolds. you will get posts that say NO WAY in salt water but i have had mine for 10 years in saltwater with no sign of "rusting out" to date. i have seen nickson al manifolds with close to 20 years in salt with no apparent problems.