View Full Version : Need to replace 1972 HM 302 exhaust manifolds

05-04-2012, 05:16 PM
Hello all . . . it seems I find myself needing to replace the exhaust manifolds and risers on a '72 HM 302 in a 16 Ski Sporter. I've just finished an engine re-build due to bad winterization/frozen block (thanks to all who helped in that thread) and now it turns out one of the ex manifolds is cracked as well. The pics aren't very clear, so if I need to provide more info just let me know and I'll give it my best shot.

Can any of you guys point me towards some sources, i.e. mfg, model nbrs, distributors, www sites, etc.? I'm hoping to just get her back in service, not necessarlily the latest/greatest thing going . . . . or does anyone have a "known good" set of them laying aroung they want to get rid of? (to the moderators - I'll move this portion to want ads if needed)


05-04-2012, 05:28 PM
the holman moody risers were made by glenwood I believe, search holman moody and glenwood on ebay another option would be barr or osco center risers . just watch the height of the risers

joseph m. hahnl
05-04-2012, 07:33 PM
the holman moody risers were made by glenwood I believe, search holman moody and glenwood on ebay another option would be barr or osco center risers . just watch the height of the risers


(http://www.glenwoodmarine.net/Catalog/COMPLETE CATALOG.pdf)

05-04-2012, 09:10 PM
i haved used OSCO

Gary S
05-05-2012, 12:47 PM
What is actually wrong with yours? I see a chip out of the mounting surface,anything else? Now that I look closer it must be a shadow.

05-05-2012, 01:02 PM
Barr marine for Fords (http://www.marineengine.com/parts/barr_marine/catalog.html?http://www.marineengine.com/parts/barr_marine/index.htm?gclid=CJO9w8HP6a8CFUFo4AodzzTP2A)

05-07-2012, 06:36 AM
Hello all,
Sorry for delayed reply - had to go out of town and had no access. Appreciate the suggestions, I'll try and look 'em up this evening. As for the problems mine have, apparently they suffered from the same "winterization/freezing" problem as did my block; i.e. there are internal cracks. When tested, water flows out the exhaust ports . .. ..

Tx again, and I'll be checking into glenwood, osco and barr this week.
Any specific limitations I need to worry about? especially w/riser to transom fitment?

05-07-2012, 07:14 AM
you'll need some wet exhaust hose if you go to the center risers. with your end riser logs there is a short piece of hose that attaches to the tips. the center riser dump is more towards the middle of the motor so that hose to the tips will be longer. you'll need to double clamp both sides of the hoses. the barr and osco come in 3 and 4 inch some of the older boats had smaller tips so you'll have to see what you have. I just did this on my boat I removed a jury rigged capt call system and had 3 inch center risers going to 4 inch tips. There are a bunch of adapters to help get the job done.

05-09-2012, 07:56 PM
OK guys . . . finally got time to check out some of the suggestions. I started Google-ing Glenwood and Barr, then found Osco. Looks like Osco not only mfg's some of their own, but is distributor for the others as well? I found them at: http://www.oscomotors.com/index.asp

So, on their site I found four candidates for Ford 302 - for both center and end risers. Other than fitment issues, i.e. overall height and length, I'm truly clueless as to pros/cons of either style or of any brand over the other . . .. . other than price of course. If you guys are familiar enough with dimensions to steer me in the right directions, it'd be really helpful - my new engine is still out of the boat, so I have know way of knowing if any of these will/will not clear the deck lid and provide enough room to connect to the transom ports.

sorry for the .pdf's - (I didn't have a way to convert 'em to .jpg's) - but they do scale up well.

THANX !! to all


Oh yeah - if anyone can recommend a supplier w/reasonable prices, that'd be cool, too.

05-09-2012, 08:11 PM
you are going to want to stay away from the pleasurecraft risers they are for a ski boat with low exhaust exits the mercruiser ones are end risers similar to what you have now the end risers can be hard on the valve train on the back cyls. the osco with the 3 inch exhaust riser with no spacer should bethe ticket . the osco have a stainless insert and a short extension seen in the pdf which means the water and gases mix in the hose not the riser not sure the barr are the same

But if it were me I would get the motor in then take some measurements before getting the risers. this way you can find wether the 10 or 30 degree angle works and that they will fit under hatch.

here is a shot of osco's on my 302

05-09-2012, 09:32 PM
here's a shot of a 1970 16 with a 302 and newer center risers so they should fit. these look to have very low or no thru hulls so making up any angle out of the risers is fairly easy

05-12-2012, 09:48 PM
Scooter - thanks for pointing me towards the Osco site.
Mattyboy . . as always, appreciate all the good input. And especially the pics; glad to know the center riser style can be fitted in. I got a lead on a pair of "older ones" that are local to me earlier this week. Supposedly they are some flavor of MerCruiser and are end-riser style. Fellow says he'll water/pressure test 'em this weekend, and if they're "OK", then I'm planning on taking a look by mid week. As for getting the engine back in before before hand, that seems to be very sound advice. I will take one of my old ones w/me when I go check on these candidates.

Any specific things to watch for in a pair of "older" MerCruisers? I'm hoping that, when compared side by side, I should be able to get a pretty good idea as to fitment . . .

BTW, the guy has offered this set at at $200 bucks including risers. At what point would you guys say Nope - just go ahead and get new ones? I didn't chase down all the prices for the ones I listed, but I did price a set on the Glenwood site at something like $1,500 plus for a pair w/risers. . .. .. that's a bit much for me, seeing as how I got the engine re-build for only $1,600 - that makes the $200 sound really good (but I haven't seen them yet either).


05-13-2012, 12:37 AM
I would bet that those "Mercruiser" manifolds you are talking about locally will NOT fit your HM FORD 302 engine.

I suspect they are for a Chevy engine.

Mercruiser never built manifolds for any FORD application that I know about.

Why put old Marine manifolds of an unknown age & condition on a new rebuilt engine ?
Too risky in my opnion~~~just to save some money.

05-13-2012, 06:36 AM
I would bet that those "Mercruiser" manifolds you are talking about locally will NOT fit your HM FORD 302 engine.

I suspect they are for a Chevy engine.

Mercruiser never built manifolds for any FORD application that I know about.

Why put old Marine manifolds of an unknown age & condition on a new rebuilt engine ?
Too risky in my opnion~~~just to save some money.


Merc had the 188 and. Higher HP pkg the 233 i think all mated to one of their drives the drive was called the 888. This was in the mid 70s. Both of these used the ford 302 as a powerplant. That's why osco lists a merc end riser replacement pretty popular pkg.

there is a hm 16 for sale out on the island right now which has a 188 replacement motor in it. I believe Forrest Colie (sp) here also has a ford merc original factory 16 that runs very well left handed and all.

here's a vid of a merc ford setup with the stock merc end risers they also made a 255 which was the 351 as the powerplant unless merc moved the dist on their chevies??????



I think if you shop the barr center riser you can get them at around $300 a side new plus maybe around another $100 for hose and clamps and the little things . The used end risers may be ok but how long might they lastis the real question. plus I would be worried that they won't quite line up with the old ones and now you don't have enough room to make up the difference. rigid exhaust hose is a bitch to work with if you can get both sides for 200 and they test ok that is not a bad deal and if you had to re sell should be easy to get off your hands

05-13-2012, 07:30 PM

one more thing, make sure the mercruiser end dumps are straight out and not the ones with the downspout. the true value of the used ones might be only to get you thru this season. I would not look at them for a long term solution.

hope this works out for you

05-13-2012, 11:29 PM
hi guys, i'm running OSCO now on my 302 fords.
how much does OSCO want for a set of risers and exhaust man's now?
do they have 302s or 351s in stock, i heard they where only making 351's?
it may not be worth running used if you have a new motor, could lead to a problem.
thescooter nick

05-14-2012, 06:33 AM
The exhausts are the same for the 302 and 351. The only difference is the stroke so the 351 will be wider and higher than a 302 so center risers in a 351 16 might have some clearance issues compared to a 302 16

I've seen the 4 inch oscos for around 900 a set but have not really shopped them

05-14-2012, 07:23 AM
if you shop around and piece meal it you can find decent deals

like these only 2 left then you would need the gaskets and riser discharge fittings


05-17-2012, 08:17 PM
Hey Guys . . . .sorry so long getting back on here - been working so many hrs lately seems I barely have time to come home, beat the wife & kid, kick the dog and go to bed !!

Anyways, I did get out the other evening to take a look at the fellow's "older" ones. Don't know if they were ever truly MerCruiser or not, but they did have the Barr name, logo and part nbrs on them. They are the end vs center riser style.

I set my port side exhaust w/riser down next to it . . . on top of it . . . under it .. . and everywhere else to compare them. Then we drug out the tape; every dimension we checked seemed spot on in terms of bolting up, ports matching, length, height, etc. and all indications are they ** should ** fit. He also had two sets of risers, one with the exhaust exiting strait down and the other exiting rearward at an angle very close to the HM ones. I think between the two choices, one of the sets of risers should be able to be lined up OK. Fellow says he's used a number of combinations in mating to the transom ports - including bending 3" copper to make the proper angles mated to the rubber hoses when needed. Says he's water tested both of them overnight and they held.

In any event, the motor is back in the boat with the externals being connected, plumbed and wired. I'm hoping to get the boat to the manifolds early next week. Then that portion of the fun begins. He's agreed if we can't get them to mount up and clear everything, then they'll still be his, not mine.

Thanks again for all the input . . . and great pics. I feel like I actually have a prayer at getting her running now.

05-18-2012, 07:12 AM
sounds like the guy is willing to work with you that's half the battle. I would think barr or osco were the ones who originally supplied Merc with exhausts when Merc was using Ford Marinized motors as part of their offerings.
good luck hope it works out for you.

Just Say N20
05-18-2012, 07:29 AM
And, as you put the engine back in, I'm guessing you can see it would have been much harder to do with the exhaust on. I'm also guessing you will find that as you start to hook things back up to the engine, you will be thankful to have the extra room to work with the exhaust not on. There isn't much room to "play" in the engine compartment of a 16. :)

05-18-2012, 07:50 AM
very true I have forgotten all about that in a 16. funny just last night my daughter is home from college for a bit and she hopped up on the ladder to say hi while i was in the bilge of the hornet putting in the starter. the first words out of her mouth was wow this is alot bigger than the red boat. she then got in on the other side of the bilge and helped me get the starter's bottom nut and bolt started. I have very fond memories of my 16 working in the bilge was not one of them LOL

05-26-2012, 07:22 PM
so 72 how did it work out for ya?

05-28-2012, 03:00 PM
Well Guys, I had hoped to have her all back together and running for this weekend's holiday . . . But, it looks like the famous "good news - bad news" story instead.

Deal is, manifolds fit fine. Bad news is the strait-down risers that were bolted up to 'em had the end of the exhaust pipe too low. And then we discovered the rest of the bad news . .. . the other risers with exhaust exiting outward were apparently from a center riser set of manifolds and the bolt pattern was no where close. Sooooo . . . back to the drawing board. Looks like I'm gonna' be looking for a set of those center riser Osco ones like MattyBoy has . . . But at least now that all the parts and the boat are in the same place, maybe I can figure which angle risers to go with .. .. .

Thanks again guys, and I'll keep you posted.

05-29-2012, 12:09 PM

that's what I was afraid off most of the ford powered mercs didn't have thru hulls they used thru the drive exhaust so the risers usually had turn downs. check online for deals on the osco or the barr manifolds

good luck