Turning a 1977 crossflow into an animal, questions?

[tfmech]

The problem with using the 77 gearcase is that it looks to be the old (early) style: not a very hydrodynamic profile-when slicing through the water. Later models have the more optimum gearcase profile. Compare the skeg appearance and length of profile between the two. You might want to put a plain "long" driveshaft into the 81 gearcase.

With out dragging the newer one out into the cold to match them up it looks like the skeg is the only difference can I cut and reshape the skeg to match. Is that the only difference or is there others. I guess the other question is how much loss am I looking at with the older piece in mph or performance.

[EMDSAPMGR]

There should be another difference. Also check the length of the profile of the lower unit. From front to back measured across the area where the water intakes are. You will probably find the later case has a longer, profile. The factory re-did the cases for a reason. Likely more efficient thru the water and the later case will have a higher blowout speed. A gearcase expert may have the exact details.

[wideglide55]

stock 235 on my Vegas 80 all day never turned it over 5800 motor would last two to three summers before needing rebuild,i ran it 25 miles at full throttle many many times with no trouble whatsoever.premium fuel with extra oil and a good fuel separator,the only way to make it live long is keep your timing at 26 degrees,if you run 30 like they say the first load of ****ty gas crossflow go boom

[skeeter91]

ok i couldnt get to my shop for a couple of days,sorry for the delay.anyway here's a couple of pics of what can happen when you run one of these in the "no-no" rpm zone!yes it made horrible noise

[skeeter91]

here are a few of a 2.6xp someone ported heavily!was real screamer,once upon a time.

[bruzercomp81]

I would recommend running that motor as is before you take it apart as long as it's in running order. I run a moddified 77 200 crossflow on my boat and I haven't tuned it yet but it spins 6400 rpm and it's really rich. A friend runs a stock 77 200 crossflow at 7000 rpm on his viking and it's stock. Once you start doing a ton of mods at once tuning is a pain and running 1 3/8" carbs on a flat back crossflow is pointless in my opinion. I think 1 5/16" is more then enough.

[tfmech]

ok i couldnt get to my shop for a couple of days,sorry for the delay.anyway here's a couple of pics of what can happen when you run one of these in the "no-no" rpm zone!yes it made horrible noise

Ouch, looks like something out of the hot rod I work on!!

[tfmech]

I would recommend running that motor as is before you take it apart as long as it's in running order. I run a moddified 77 200 crossflow on my boat and I haven't tuned it yet but it spins 6400 rpm and it's really rich. A friend runs a stock 77 200 crossflow at 7000 rpm on his viking and it's stock. Once you start doing a ton of mods at once tuning is a pain and running 1 3/8" carbs on a flat back crossflow is pointless in my opinion. I think 1 5/16" is more then enough.

I am planning on firing up the 200 first when we finally get some nice weather around here. It was a running motor and had good compression. I will just see will probably start off the year with it. How often does your friend have to rebuild it? I am not afraid to twist it up but I don't want to hit 7G and have it last 30 seconds. If I need CHT gauges and egts I will install them if that is what it takes to tune it and make it live for a while anyway. If it lasts the maybe five times I will get a chance to take it out this summer and I have to re ring it next winter I will be happy. I just want to come out of the cove on the open water and run 75-80 down to the floating bar

[bruzercomp81]

He ran it for 3 years like that and because of too hot of spark plugs (you need to run surface gap plugs) it burnt a piston after holding it at 7000 rpm for about a mile. It was a really stout motor and he never had an issue with it. The only thing done to it was boyesen reeds. The motor on my boat is very modified and have only had it out 3 times but I'm not sure of the logjevity of it yet.

[tfmech]

He ran it for 3 years like that and because of too hot of spark plugs (you need to run surface gap plugs) it burnt a piston after holding it at 7000 rpm for about a mile. It was a really stout motor and he never had an issue with it. The only thing done to it was boyesen reeds. The motor on my boat is very modified and have only had it out 3 times but I'm not sure of the logjevity of it yet.

What boat was he running it on? What all do you have done to yours??

[tfmech]

A couple of you guys have said the nine pages mods are too much for the weight I am going to be pulling and that it will not wind up? My question is why? Why will it not wind up to much weight? I guess prop choice would come into play? Will is just take to long to get the rpm because the motor is not making any low end because I have raised the power band? With the nine pages what RPM would I be able to turn.....or is there a better porting setup. I am getting ready to gut the hull as soon as I get some nice weather. It is getting a new floor (maybe the stingers and transom too), two factory captains chairs and the fuel tank......guess I will leave the bilge pump might need it

[bruzercomp81]

He was running it on a hydrostream viking before it blew up and we put a different motor on. My motor was built by Rob king and was made to swirl the air going into the cylinders like on a hot rod car motor. Everything is smooth and matched perfectly. The ports are squared and the cylinders are scalloped. It doesn't sound like much but if you saw it compared to the inside of a stock motor there's a lot of work done. With these motor it seems like the more work you do to them the less low end you get. These motors were only designed to really spin 6000 rpms on a fishing boat and not much more so when you get over that with a heavy boat your just falling off the power band. I guess with the right prop and a long lake you could get it to high rpm but it seems like the only way to push a big boat with a crossflow is to put high compression on it and say good bye to longevity.

[wanagofass]

Let's see some pictures of that swirl work bruzer.

[bruzercomp81]

This is the only pic I have but most of the real work is in the exhaust. I don't have a pic on my phone but if I take it apart again i will take pics.

[hq_]

One thing I've been wondering for a while is that can the exhaust stuffers from an early 70's 135 be ported to match the later, 140 (and prop-rated 115) pattern and if yes, would the benefit be worth the trouble? There isn't much extra meat in the cast bubble manifold so any extensive porting is pretty much out of the question, but in addition to some smoothing, converting it to "140" pattern might be worth it if it's doable.

I just dug out a bunch of xflow parts from two different engines, laid them on a table and tried to figure out how much the flow can be improved in various places. Intake manifold is quite obvious but the whole exhaust side is a bit trickier to figure out, especially when I've never had a chance to take a close look at a modified or even a stock 140 for comparison.