OMC Research

[DieselDood]

Hey guys

I have a 175hp Crossflow that needs a rebuild.
I'm debating just slapping 2 sleeves in it with 2 pistons and run it as is and be happy.

Or... Whoever rebuilt it before has 3 different bore sizes.

I could do 4 sleeves and return to stock 3.625 bore sizes, build it "right," and do the build it a bit more stout.

Right now the ports are what I have read, are called Figure 8 ports. Its 2 holes that look like someone simply drilled 2 half inch holes side by side all the way through the intake and exhaust of the sleeve.

What porting can be done that isn't crazy to get more out of it.
Whoever rebuilt it before already did the Larger carbs (can't remember size 1 3/8?), Bubble Back, Reeds and intake stuffers with the 8000rpm CDI boxes.

This will be going onto an 89 Skeeter SK1700 Bass Boat. So I won't be officially drag racing, but if you've been to a Bass Tourney Blast Off... it is kind of a race! LOL

What would you guys suggest? Is it worth putting the extra 2 sleeves into it? What is the max power you guys think is reliable?

[keefallan]

Your ports don't sound right at all. Can you post pics? There should be 3 ports on both the intake and exhaust sides of the sleeve. The engine came with 3 holes on each side, a bubble back exhaust and 1-3/8 carbs from the factory......based on the fact that you said it has 3.625 bores......a big bore 175 not the small bore 175 of earlier years.

[DieselDood]

Interesting.

I'll pull the covers off this weekend and get some pictures.

I'm hoping that I don't need to resleeve the whole thing due to the hack that rebuilt it last....

[Merc 2.5]

Interesting.

I'll pull the covers off this weekend and get some pictures.

I'm hoping that I don't need to resleeve the whole thing due to the hack that rebuilt it last....

People tend to think all u gotta do is pull sleeve and put new one in but just cant do that , especially if it got hot at all

[racer]

That engine the old sleeves have to be bored out, they do not pull after heating like the loopers do.

[flabum1017]

That engine the old sleeves have to be bored out, they do not pull after heating like the loopers do.

Yeah the sleeves are splined from what I remember

[Mark Poole ModVP]

OMC called them dual overlap ports. Normal on certain cross flows. On the V4's the 85 h.p. had small round ports.

[billybob]

I am sorry, but I can,t reccommend rodding or rebuilding those crossflow motors. The inherrent problem is the big dome on piston. The dome retains heat, and they will stick a piston much sooner, than any looper style motor. You are always better off keeping them as close to stock as possible. Then when you start adding sleeves, and port somehow gets enlarged. Then stock jetting is not big enough to save motor, from sticking a piston again.

[ChrisCarsonMarine]

What size bores are they,and which are how hurt.No problem to bore,and no reason mot to,up to 040.PIA to resleeve,better to find a borable block if yours isnt.

[DieselDood]

Bore sizes I'll have to double check my slip I wrote down at home, but 2 were 3.625, 2 were as I recall 20 over and 2 were 30 over.

They weren't companion cylinders either... I believe it was 2 and 4 were 3.625, 6 and 1 were 30 over and 3 and 5 were the 20 over. 5 has a crack so that sleeve HAS to be replaced. 3 is the cylinder that has a hole in the piston and a little ball of slag at the bottom where the sleeve meets the block. That one I believe could be saved.


I don't mind doing the work for rejetting. I have a buddy that works at a marine shop in town and said he can grab different size jets and I wouldn't have to pay for the whole pile to do testing. Just the ones I want to keep.

From what I can tell, cylinder 5 let go before. Someone put a sleeve in it and had to do some grinding repair to the lower part of the block that goes around the sleeve.
I don't think it's an issue, but I'll get some pics.

I didn't get a chance this weekend as I was chasing my other issue (low fuel pressure) from my other post. The pump rebuild kits I got weren't correct, they were to tall, so I modified the diaphrams slightly by adding a hole where it needed to be. I still had the same low pressure issue, so I added an electric pump that is rated 4-7psi and 73gph... And retested... apparently my gauge must read low, because it's still reading 3-4psi. I have a hard time believing that a brand new Delphi pump would be that low. I'm going to guess my 25 year old gauge is bad.

I'll take it out on the water today and find out though....

[DieselDood]

Sorry for my horrible description of the ports, here is a picture as requested.

[z1rider]

I'm doing a Evinrude XP 175 also. Started with all 6 pistons at .020 over. All 5 are lightly scuffed, and 1 is badly scuffed. Thinking it ran without oil, VRO? I just got off the phone with the boring shop. Going to do all 6 @ .040 over, and use Wiseco's. So much for a quick 1 cylinder bore, and hone the rest for a quick, and (cheap), fix. $$. I'm running the higher compression heads, 325638/325639, also. Jetting looks to be stock @ 62's.

[DieselDood]

I wish I could just bore, but i have one sleeve that is cracked. So at a minimum I HAVE to do one. At that point... do I just bite the bullet and bring it back to stock bore size or let them be all different sizes.....

[z1rider]

I would just replace the one sleeve, and have it bored out. Get those cylinders dialed out, first.

[racer]

Z1 the heads you installed will need more fuel than the stock 175 and less timing