Old 235 Crossflow Failing

[SRP71]

Got a couple of questions for my Old 1984 Crossflow 235 (E235TLCRC)

Trip before last motor was running fine all week until last day when idling into marina.
When I was almost to the dock it sounded like the Motor was not firing strong on all cylinders. Motor was jetted for Lower altitude and we were on a very high mountain lake. Figured it was just jetting. We pulled skiiers all day no problem and had about a 6 mi High speed run back to the marina no problems.

Took boat out yesterday and motor would not run and was dificult to start. Once I got it started it would not run ove 1500 rpm to about 2000 RPM. Sounded ike it was not firing on all cylinders kind of like fouled plugs. Checked Bulb while on the water and it was firm, when trying to take off I primed the motor with the key primer, this didn't help. checked Recirc check valves and they are fine.

Went home and put in a new set of plugs and problem didn't improve at all. Started it on the hose and the idle seems weak like it is partially firing on some cylinders.

Tried the River again after replacing Plugs and motor seems dificult to start, idle is rough. Can bump throttle and motor will rev up. If put in gear at idle it nearly dies. Floor it and it wont accelerate only gets louder. Verified advance lever is moving timer base.

Running 638/639 heads cut .030 Compression is 110 Psi warm on all cylinders at an altitude of 4550 ft above sea level. Running the newer OMS pump replaced last fall.

I feel that it is ignition and need confirmation that it might be power packs and coils.

Any tests I can use to determine this? Have access to Digital VOM.

Before this problem the motor ran strong and never missed a beat. In fact the lake we were running at was 6700 ft above sea level and it could still pull a slalom skiier fairly quick out of the hole and still top out at 55 to 60mph with rich jetting.

Using 100% synthetic oil and 93 octane. I think almost all of the coils are the original ones and not sure how old the packs are. New BRP coil wires 120 hrs ago.

Thanks, Scott

[stickmanc]

Scott, have you checked for fire on all cylinders yet?

[SRP71]

Yes I checked and all cylinders do fire. I verified this by disabling one coil at a time and then starting motor. Only diasabled one coil at a time. Also every plug is hot when it has ran a few minutes. Don't have IR temp probe but by feel they seem the same.

I think its a power pack but would like to know for sure. I don't think its the timer base because motor does respond to manually advancing the timing manually. and the Stator does charge the batts because if I run lights ect with motor off the volts on the batts drop a little.

Scott

[Neveredge]

If you are running the 638/9 heads and they are cut .030 and your only getting 110 psi then something is wrong. Even at that altitude you would need really good fuel with that head combination. Also, you need to be mixing your own oil and fuel. The stock 2.6XP requires 26 to 1 ratio with stock 638/9 heads and yours are cut. I know you have 235 porting but the oil is needed with those heads. The oms doesn't provide enough oil at full throttle or under heavy load.

Try replacing the ignition parts one by one until it improves. ( it never hurts to have spares) if none of this works pull the heads and look for scoring. This is what I think it is. To much load and not enough oil. That has killed many 2.6s. because guys mix them at 50-1 instead of 26-1

I just saw where you said if you fkloor it it only gets louder but doesn't accelerate. Does the rpms increase when you do this? If so you could have a lower unit problem.

[SRP71]

Thanks for the advice Neveredge. The boat does accelerate when I floor it. It just wont increase RPMS much above 2000 rpm. Can hear the noise of motor with carb barrels wide open (louder noise)
LU is fine nice firm shifts. I will add extra oil to the tank I guess to compensate for the OMS. 26:1 seems a little heavy. How do you get away with that on a lake ?
(Smoke Trail City on take off)

I might up the ratio to 40:1

Seldom run WOT for more than min or two. Usually run motor no more than 4000 rpm as I use it mainly for skiing. Have a prop that shifts from 16 pitch at take off to 22 pitch on plane. Motor revs up to about 5000 rpm before shifting (Adjustable with turn of knob. (Not the L&S Prop). Motor never lugs down. If pulling tubers motor wont shift, if going slow motor wont up shift. Speed has to be above 25 and rpms about 4500 to 5000 before it will shift to 22 pitch. Makes for awesome hole shot and great top end.

Low PSI might be altitude but I agree it seems low for 638 heads. The Batts were getting tired after several cranks on the motor.

Before I had the 638 heads the comp was 85 to 90 psi. Might be faulty gauge?

When I replaced the heads I checked bores and they were fine no scoring and the the bores were still within tolerances. ( not out of round). Thought I would see issues.

Could reeds cause low comp? Have had the same reeds since rebuild 3 yrs ago.
(Boysen Reeds)

Thanks, Scott


I went ahead and ordered new packs and coils as it appears that the ones it has are original or close to original.

Will let you know the outcome of that

[Neveredge]

The standard 235 heads would produce about 90 psi.

Yeah 26-1 seems high but that iss what is called for in my 2.6 manual.

At lower rpms you don't need as much oil as the motor is already richer than it needs to be for any given rpm. This is why the OMS/VRO is able to use less oil. If you aren't going full tilt boogie you should be OK. Just add a little oil when you are out screamimg and flyin.

[SRP71]

Thanks neveredge for the advice, I will remember to add oil to the tanks if planning on some long high speed runs. With fuel prices as they are for premium it makes you think twice about running it WOT very long

I usually add some Toluene to the mix if I plan on running it hard, A little more oil wont be a pain to add as well.

I thought the new OMS was a constant 50:1 regardless of motor rpms. I think that the old VRO could lean the mix down to 100:1 at idle or low rpms. I could never understand how a motor could survive very long if you idled it out of the marina for more than a few min and then expect to run it hard, as the carb bowls would be full of a lighter oil mix until that gas was burned.. When I rebuilt motor I upgraded to the OMS for that reason and for the fact the VRO was probably at least 14 yrs old. ( oh and I don't like to pre mix)

Glad to see a fellow S&F'r on BBC

Love this board just as much

Should I be concerned about the 110 PSI? or just run it? How long will Boysen's
last?

Thanks, Scott

(AKA Crossflow235 on S&F)

P.S. Nice FrankenRude motor Wish it would fit my crossflow mid.
Hope you dont have to sell it Looks like you put a lot of work into it.


Modified by SRP71 at 10:04 PM 7/31/2006


Modified by SRP71 at 10:04 PM 7/31/2006

[fishy]

FWIW - I have a full used set of igntion components for your engine. Power packs,coils,stator,flywheel, recitfiers,etc... It's all stuff that is just sitting on a shelf in my garage.