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  1. #1
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    235 Crossflow - won't hit WOT. Probably fuel , but want to check with tthe pros...

    I have been running a 1979 235 Crossflow on my 20 ft. Sea Ox for a few years. Got it for a bargain with no history. Turns out it was likely rebuilt then put in a garage. Great compression and leakdown but ignition and charging sytem seriously fubared. Probably why it was put in the garage. Swapped on a spare 1985 Crossflow 35 amp system (single power pack) I had and it's been running great - very stout.

    Last fall the fun started. Coming off a plane, I looked back and noticed white smoke coming out of the cowl vents. Turns out the voltage regulator caught fire. Got the fire out, disconnected the alt and drove it home with no more excitement. Swapped in a new voltage regulator and was able to resolder the stator leads and save it. Power pack seemed OK too. It's been running fine all summer, but...

    New problem last week - Motor won't go over about 3,000 RPM (it's propped for 5,300). It runs perfect at idle and up to about 3,000 RPM. First thought was fuel. I found it puts out 5-6 PSI at idle but approaching 3,000 RPM drops to 2 PSI and one or two cylinders drop out and it just hangs there. It doesn't run choppy, just drops what feels like 2 cylinders. The OMC manual says that 2.5 PSI should be enough, so I'm not sure it's just fuel. I tried pumping the primer when it's hanging at 3,000 RPM and I can get the two cylinders to fire and it will bump up a lot but gets a funny up/down RPM oscillation like the power pack is on the rev limiter, but it's only around 4,000 to 4,500 - couldn't tell for sure because I was alone on the boat, doing gymnastics trying to see the tach, see the fuel pressure gauge on the motor, pump the fuel bulb while trying to steer - what a circus.

    So I have a few questions:

    1. It 2 PSI too low for this motor? If it is, are the fuel pumps rebuildable or do I need to go new?

    2. Could the power pack also be on a low rev limiter for some reason - spoofed head temp sensor? If so, can I just disconnect one/both sensors to see of that's it? I'm sure the motor is running at right temp - new impeller, t'stats, grommets, clean water passages and it runs 20 psi at WOT - heads are warm to the touch, not hot.

    Advice much appreciated.

    Thanks...Steve2ManyBoats.

  2. #2
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    According to my 1978 factory manual, the fuel pressure should be between 2 1/2 lbs and 6 lbs, measured just after the second pump, before the fuel distribution tube to the carbs. Not sure just what ignition system you have on the engine. The 1985 through 1988 35 amp systems still used two power packs-similar to the original ones on your 79. In 1989 the 35 amp V6 crossflows converted to the single power pack and added two new features: SLOW and Quickstart. That SLOW system would limit rpm's to approx 2500 rpms when the engine sensed an overheat from the temp sender in either/both heads. Disconnecting the two knife leads to the head temp senders (for a test run) to see what happens to the top end rpm's should tell you something.

  3. #3
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    Thanks for the reply.

    Hmm...Now I'm more confused. I'll have to check the model number on the carcass I got the ignition system off of. Must have gotten the year wrong. I know it was a VRO motor and it has a single rectangular power pack, not the two wedge shaped ones the 79s came with. Didn't know about the two idle settings. Mine never idles fast at start up. Pretty much starts like all V6 Crossflows I've come across do - grumpy for about 30 seconds needing a little fast idle then settles down to about 800. Below that it loads up.

    I checked the fuel pressure after the second pump before the line splits to the carb when I got the 5-6 PSI at idle falling down to 2 PSI at 3,000 RPM. I found a couple of fuel pump rebuild kits locally and I'll rebuild the pumps this weekend. If it still won't hit WOT, I'll try removing the two temp sensors from the circuit to see if that makes any difference.

    The reason I went to the 35 amp system, other than the fact that the stock ignition system was in bad shape, was because I wanted more charging capacity for a fishing boat. Other than the idle differences (which I haven't seen to date - not sure why) are there any reasons why that ignition system wouldn't work on this 79 235?

    Thanks again for the insight...Steve2ManyBoats.

  4. #4
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    I think the ignition system will work out fine. You may not have noticed the Quickstart feature. It advances the timing a few degrees until the engine reaches something like 92 degrees. My guess is that you don't have the later temp switch in the head which will signal this feature. Not a big deal. My neighbor has this on his 89, and it still sputters somewhat for the first minute after cold start anyway. The only difference to me is that the single pack is rev limited at 5800, whereas your original factory 1979 dual power packs were unlimited. That 235 still makes good hp right up to 6000, so if you did ever prop it for speed, you might consider another pack with a different rev limit.

  5. #5
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    You guys are confusing me too, as far as I know, the V6 Crossflow;

    Used only two rectangular power packs, one one each side.

    Was only Mfg untill 1985.

    Never had Quick Start, thought that came out on the Loopers (1986 on).

    The temp sensors in the heads operate the warning buzzer and nothing else.



    I would start by cleaning the carbs first (fuel these days is crap).

    If your tach is not working, you probably have a bad stator and/or voltage regulator.

    When you get this straightened out you should prop your motor to turn closer to 5800 rpms or you could melt some pistons.
    Last edited by john j 80 viking; 10-18-2010 at 03:36 PM.
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    58' Farmall Cub

    Is that your mama's boat?

    "I said I didn't have much use for one. Didn't say I didn't know how to use it."- Mathew Quigley

  6. #6
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    They made 235Hp Crossflows intill 85'... they continued making smaller 175hp (2.6L) up to 91' or 92'. Those motors were at one point were updated with the newer single pack ignition...
    Last edited by Baja16; 10-18-2010 at 04:44 PM.
    Dan Cario

    1994 STV Mod-VP w/225HO Ficht Evinrude
    1987 22' Velocity w/225HO Evinrude E-Tec

  7. #7
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    EMDSAPMGR...

    Ran the serial numbers on the carcass I took the ignition system from. Turns out it's a 1989. I knew about the 235 power packs being unlimited, but my application is a heavy 20 ft. center console. I swing a 17" Viper prop and just hit 5,300 at about 50 mph, so I'm not worried about getting the last few R's.

    Got the 2 fuel pump rebuild kits at the local stealer and will rebuild both this weekend. The RPM oscillation still has me a bit stumped. Hopefully all problems will go away with sufficient fuel pressure. If not, I'll be back...

    Thanks...Steve2ManyBoats.

  8. #8
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    Quote Originally Posted by Steve2ManyBoats View Post
    my application is a heavy 20 ft. center console. I'm not worried about getting the last few R's.
    Its about not blowing up your motor.
    NRA Life Member


    58' Farmall Cub

    Is that your mama's boat?

    "I said I didn't have much use for one. Didn't say I didn't know how to use it."- Mathew Quigley

  9. #9
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    The RPM oscillation still has me a bit stumped.
    If you are not getting enough fuel, it could cause a surge. If it picks up when you pump the bulb, you have a fuel delivery problem.

  10. #10
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    Make sure your fuel delivery is ok. Double check the antisiphon valve and be sure the ball valve is not sticking.

  11. #11
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    Valve function question...

    EMDSAPMGR:

    You're talking about the innards of the primer bulb, right? If so, if I still get low fuel pressure readings after rebuilding the pumps, I can change fuel primer bulb. If still low, I can go to a portable tank.

    The oscillation thing is still a puszzle. When the motor was hanging at 3,000 RPM, running on what seemed to be 4 or 5 cyls, I squeezed the primer bulb a few times really hard and caught the missing cyls, but the motor still had a weird RPM oscillation at about 4,500 RPM (800 RPM short of normal WOT) - like twice a second for about 5 seconds until the fuel pressure dropped, a couple of cylinders dropped and RPMs dropped to about 3,000 again. Seems like a fuel starvation problem for the missing cylinders for sure, but once I pump the fuel pressure up, it sounds like it's bouncing off a rev limiter. Very strange. I only ran it like this for a few seconds. Didn't want to score any cylinders due fuel starvation.

    I was thinking of a carb clog problem in addtion to a low fuel pressure problem, but it starts, idles and runs up to 3,000 RPM perfectly.

    I'm interested (concerned) what will happen this weekend when I rebuild the pumps (boat is 120 miles away at beach house).

    Thanks...Steve2ManyBoats.

  12. #12
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    Steve,
    You can have a problem with the ball valves in the primer bulb, as well as the ball valve in the anti-siphon valve on the top of the built in fuel tank. I've seen grit/debris in the ball valve of the antisiphon valve-it restricts the ball movement, restricting fuel flow and won't let the engine rev out. A lean condition that is not good-tons of air flow, but restricted fuel flow. There is also a chance that you got some random dirt/debis in one of the jets of the carbs. It is possible to have it run great one day, then fall on it's face the next. I tore all my carbs apart when it happened to me-found a sizeable spec of black fuel hose lodged in one of the high speed jets. That was about 3 months after an engine overhaul-with all new fuel hoses, too.

  13. #13
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    Quote Originally Posted by Steve2ManyBoats View Post

    I was thinking of a carb clog problem in addtion to a low fuel pressure problem, but it starts, idles and runs up to 3,000 RPM perfectly.
    You need to think of a carb as having three different systems that overlap.

    Idle, midrange, and high speed, they are three distinct systems.
    NRA Life Member


    58' Farmall Cub

    Is that your mama's boat?

    "I said I didn't have much use for one. Didn't say I didn't know how to use it."- Mathew Quigley

  14. #14
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    the advice about the boat's fuel system is good advice...and to eliminate it from your testing, use a portable tank with fresh fuel.

  15. #15
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    No joy - what a circus...

    Well, I found a pinhole leak in one of the two fuel pump diaphragms and rebuilt both pumps. Now I get 4 psi on the gauge. Tested the boat and no change. Drops cylinders off and won't go over 3,000 RPM. Still showed 4 psi at this speed.

    Figured it was one or more clogged jets. Tore down all three carbs and pulled the jets. All were whistle clean, clean bowls and floats properly set.

    I'll go out tomorrow with a timing light to see if I'm dropping cylinders on ignition.

    Quick question - which NGK standard plug should I use - 7, 8 or 9 heat range?

    Thanks...Steve2ManyBoats

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