1989 85hp WOT only 4300rpm

[TWPilot]

Same problem as last year. Had the boat out on the water yesterday. Over the winter, I replaced the reeds, reed backers, screens and gaskets on the recirculation system, thinking that was the last issue. Screens were gunned up, and it looked as though the backers were holding the reeds flat. So, new ones on...

After a day on the water: Idles fine (a bit choppy). Starts every time. Doesn't die. From idle to WOT- it seems a bit "choppy" while accelerating, but gets up to speed fairly quickly. Will max out at 28mph, and 4300rpm. Thought long and hard about it on the way home, and after putting her away in the garage, went back out and pulled the plugs. #2 looked a bit wetter than 1 and 3. I'm thinking #2 either isn't firing, or is firing intermittently.

Here's my dilemma- I'm going away for work for the next 5 weeks. When I return mid-June, I'll either have a week, or I'll have a few weeks to trouble shoot this. Last year, I put in-line spark testers on the plugs and they seemed to work in the garage (didn't fire her up all the way as it wasn't on the muffs. Set timing, and checked with the timing gun that all cylinders were firing. They seemed to work, although the gun is quite old and was only looking for the light to trigger for #2 and #3. So, with all that said, I'd like to order parts and have them here for when I get home and can maximize my time.

So, does the hive mind think I've got an intermittent coil, a CD, or a trigger? Has anyone had an issue with a coil missing intermittently, or something of that nature? On second thought- if it was intermittent that I'm missing a cylinder, then there would be times when that one came back online, and would max out power. So- should I just order new coils? In the electronics world- it's called "easteregging" when just randomly replacing parts- even if educated guesses are involved.

Thanks for the help all!

 

[jerryjerry05]

I seriously doubt you'd get 4300 if the motor was missing on one cyl.
Things to look for: load in the boat, motor not trimmed up, wrong prop(what's on there?) what size boat.
Try running with the cover off? Tank vent line clogged?

 

[Nordin]

As jerryjerry says check the prop, what size (pitch) and check the load.
Force 85Hp 1989 should be equipped with Prestolite CDI ignition two CDI boxes and three ignition coils (black or blue color).
One thing you can do if you have not done it is to check all the lugs under the shrink tubes for the ignition system.
These very thin wires tend to break under the shrink tube and can cause ignition issues.
Pull with a little bit of force at all the thin wires and check for bad connections.

 

[puffitu]

I second the wire tug test as Nordin spoke of; I had a similar issue and actually found two wires which were hanging by a thread and another was just riding in the shrink wrap held in place by the mere stiffness of the the wire itself. After that if it were me ic start checking the packs and coils; the plug and play connections can loose contact as well.just my 2 cents

 

[TWPilot]

Thanks guys. Will do the tug test.

It's an 89 Glastron 16', with a 17p prop. It had a 21p prop on it when I bought it, and would only get to 4100rpm. I think I may have put a bit more weight in it with the "extra" fiberglassing I did- i.e. I layered more than stock over the new stringers/floor, but perhaps not too much more. When trimmed, 4300rpm is the most it will go.

Compression (cheap HF gauge) is reading 95psi in all three cylinders, so either I've got a weak gauge (once again, all three reading the same), or I do have low compression in all cylinders- which would explain the cause better than intermittent firing.

 

[Redbarron%%]

I can't speak for the 85 hp outboard, but my 90 hp sport jet would turn 42-4300 rpm with one cylinder not working. The absorbed HP increases on the square with RPM so those final revs contribute more than the first.
With the 17" prop perhaps is is loaded less?
Of course the Sport Jet is a fixed pump as the impeller is located in the jet pump. I would check the power underload tied firmly to the dock and a safety person while checking for spark with an induction timing light.
Clean the plugs or install new plugs. do the test at WOT tied to the dock and shut it off from full throttle and look at the plugs for a wet one or one not firing.

 

[jerryjerry05]

Harbor Freight Gauge = crap results

 

[puffitu]

Harbor Freight Gauge = crap results

I second that notion; )