1984 150 crossflo

I had my powerhead replaced rebuilder said new one is a 200 hp. it has a flat exh. cover, any way to tell the differance?

Re: 1984 150 crossflo

OMC did not manufacturer a 200hp in 1984, however the eariler 200hp crossflow blocks would interchange. Look on top of the block, on the port (left) side near the head gasket. There should be a core plug there (looks like a small quarter sized freeze out plug) that would have the model number on it.<br /><br />If it's there, get the number to us and we'll tell you what it is.<br /><br />Note that even if it is a 200hp block, in all probability you're using your original 150hp carbs, intake manifold, etc etc so you're really not going to develop 200hp. Usually a swap of that kind works out perfectly so don't go jumping to any negative conclusions. He may have performed a favor to you. Let us know what you find.

Re: 1984 150 crossflo

thanks for the reply,the number is 1200ti csm 5354073. The motor had broken timing bracket so we used the 150 intake and carbs rejetted to 1984 200hp spc.the exh. has the flat back cover. the motor doesn't seem to have as much power as the old one that had a weak cyl.timing had to be set at 32 deg. to get what we have. I am running double oil ,vro and oil in tank about half gallon in 30 gals of gas. I have had it out only once do to weather only getting 4600 rpm . mech. said that is a little low, looking at forum it should be close to 6000 to keep carbon from building up which I now think was problem with old motor.

Re: 1984 150 crossflo

Are the carb throats the same diameter on the 150 vs. the 200?<br /><br />Thanks,<br />Duck L.

Re: 1984 150 crossflo

thanks for the reply not sure on carbs I don't have the ones from 200 hp I am useing the carbs and intake from the 150 hp should I measure at the intake or block

Re: 1984 150 crossflo

The carb size is cast in on the front of the carb. The 150 cf and 200 cf have different port timing and port areas. <br /><br />To see any significent difference you would have to be maxed out on the 150 set up and have a hull (Hydrostream, Allison etc) that responds to small torque increases.<br /><br />A lot depends on the heads you have also.<br /><br />Good luck!

Re: 1984 150 crossflo

this boat is a 21 ft center counsol it used to run 40 cruise 32 now run 34 cruise 24 if it is a 200 hp using 150 intake and carb do I jet for 150 or 200? would it be ok with this intake and flatback exh. or doI need hump back exh and different intake?

Re: 1984 150 crossflo

The 150hp and 200hp both use the flat exhaust plate. The "200" and the "CS" in the model number indicates the powerhead is a 1980 200hp model.<br /><br />I'd suggest that you install the proper 150hp jets as you are using 150hp carburetors. It's logical that enlarging the jets would simply make the engine run rich which would restrict the top rpm.<br /><br />There's usually a difference of 2° in the full spark advance timing between the 150hp and the 200hp models, and since you've now got a mixture of a 1984 150hp and a 1980 200hp, I'd suggest you find out what those timing specification are and use the lowest setting.<br /><br />DHadley..... what are your thoughts pertaining to the full spark advance timing?

Re: 1984 150 crossflo

thanks joe,I will rejet carbs,we went with lower timing 23 deg. the motor was a dog topped out at 20 mph loaded up and quit running tried 32 deg. it ran decent, tried a little more 34 no improvement so went bact to 32. Do I just need to put a few hours on this before I get worried ,or am I in need of minor adjustments to get my performance back?