Bad plug wire- 89 force 85hp

TWPilot

Seaman Apprentice
Joined
Feb 26, 2020
Messages
34
Welp, finally had an actual problem on the water last weekend. Was going "great" at only 4300rpm, and all of a sudden, it bogs down and will now only do 3000rpm. I get home, check compressions- and everything is as it was (95psi on all three with a cheap HF gauge). Start it up, and pull #1- no change and a helluva shock as I'm pulling the plug wire. #2 and #3 showed a noticeable drop in rpm once pulled- and no shock. SO, I was thinking bad plug wire. Ordered 3 new coils (they're 30 years old anyways), which came with new plug wires. On the water tomorrow- we'll see if that fixes the problem, and also the original problem of only getting to 4300rpm...
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,049
If it's an 89 you can just about bet the wire's bad. :(
I thought the plug wires were part of the coil and couldn't be replaced????
Post a pic??
I've changed the plug boot and covered the wire with double shrink wrap and liquid electric tape(actually worked)
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,349
Welp, finally had an actual problem on the water last weekend. Was going "great" at only 4300rpm, and all of a sudden, it bogs down and will now only do 3000rpm. I get home, check compressions- and everything is as it was (95psi on all three with a cheap HF gauge). Start it up, and pull #1- no change and a helluva shock as I'm pulling the plug wire. #2 and #3 showed a noticeable drop in rpm once pulled- and no shock. SO, I was thinking bad plug wire. Ordered 3 new coils (they're 30 years old anyways), which came with new plug wires. On the water tomorrow- we'll see if that fixes the problem, and also the original problem of only getting to 4300rpm...
What seize prop is on it? (the pitch?) on what seize boat?
 

puffitu

Chief Petty Officer
Joined
Dec 30, 2018
Messages
555
What seize prop is on it? (the pitch?) on what seize boat?
Not sure prop size has anything to do with his issues here but I reserve the right to be wrong; according to his description of what he’s experiencing
 

puffitu

Chief Petty Officer
Joined
Dec 30, 2018
Messages
555
The wrong prop can drop the rpm's a lot.
I understand the wrong prop thing but…He said all was going great at 4300 rpm until all the sudden…now the thing won’t go over 3300??? there’s no way his prop problem suddenly began at that speed -please correct me
 

The Force power

Commander
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Feb 3, 2019
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2,349
I understand the wrong prop thing but…He said all was going great at 4300 rpm until all the sudden…now the thing won’t go over 3300??? there’s no way his prop problem suddenly began at that speed -please correct me
I meant to say that 4300 rpms full tilt is not "great" and could be caused by a wrong pitched prop
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,049
MAYBE??? the tach is set wrong? Look at the back and see where the black arrow is set??
But a 1000rpm drop could be a coil, stator, diaphragm etc.
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,349
Exactly! This thing should be a bullet-not the prop
Yeah, we got distracted by the prop.
Inspect the diaphragms in the fuel-pump/the vent in fuel-tank
Also verify all trigger-wires & their ends by gently tugging on them
(they tend to break under the shrink-tube)
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
38,043
Maximum RPM of 4300 as indicated by the OP should be investigated.-----Up to the owner to find the issue.----And yes it could be the tach itself.----I can not see , touch this motor.
 

TWPilot

Seaman Apprentice
Joined
Feb 26, 2020
Messages
34
Thanks for the extra replies, guys. The tach is an aftermarket generic one- and unsure of the settings (I followed the directions for the set-up). I replaced all the gauges when I replaced the stringers/transom/floor, and changed nothing on the motor. The rpms were the same as the factory tach prior to "disassembly" of the hull- so I'm fairly certain the setup is correct. The engine was performing exactly as it had prior to the restoration. Since the restoration, I replaced the fuel pump diaphragm. During the restoration, I put in a new tank and ALL fuel lines are new. There is no "sputtering" or missing while at WOT- I did a 15 mile trek yesterday from the cabin we rented back to the landing where we put-in.

I think I may have found another issue, though- and this may or may not cause it. I've performed the link and sync many times, and made sure that the "tickmark" on the cam was pointing at the roller on the throttle linkage. Hole-shot starts were adjusted day before yesterday by "tweaking" the low rpm screws so there is no hesitation nor bogging from idle to WOT. However, full throttle still leaves about 30 degrees on the butterflies, never getting close to fully horizontal. Perhaps I don't have the correct throttle cam on this thing? SO, this morning I re-adjusted it so that it has full travel by extending the linkage to the cam from the timing tower, and re-adjusting the roller so that when the throttle lever is in the upright (closed) position, the butterflies are as well. At full throttle setting, the butterflies are now in the full horizontal position. Timing is spot-on, so I wonder if the extra thirty degrees of deflection would have any bering on the low-rpm issue? Perhaps it's running too rich at WOT, with fully advanced spark, but restricted airflow?

Taking her back up to the lake to find out if this did ANYTHING... Will keep you guys posted.
 

TWPilot

Seaman Apprentice
Joined
Feb 26, 2020
Messages
34
Only thing that did was improve throttle response. It's still "capping out" at 4300rpm. At this point, it's probably just tired and requires a rebuild. I'll just enjoy it this summer- or until it truly gives up. If it lasts the summer, I'll rebuild it over the winter. Once again, thanks for the replies!
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
18,049
The butterflies don't have to be horizontal at full throttle.
They can actually go past that at full throttle.
What's the compression readings? low comp and the motor wouldn't start or be real hard starting.
IF??? you get 4300 then the motors not "tired"
I'd get a "tiny tach" and see what the reading is then??
My twin 88/85hp. had over 2000 hrs. when the transom clamps broke from salt water corrosion. They started and ran great until they were removed.
 

WinnerCougar74

Petty Officer 1st Class
Joined
May 12, 2020
Messages
238
Just to give you a comparison. My 1974 Chrysler 135hp would only get to 4500rpms and 38mphs at WOT with a 19 pitch prop. The boat is a 19ft Winner all fiberglass. Weighs about 1800 lbs. When I switched to a 17 pitch prop it can go to 5500rpms and 34mph. I have done a lot of tuning but these numbers have stayed about the same. Tach is original to the boat and motor.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,049
you say 17p 19p
Is it a 17x13 or 17x131/2
Same with the 19 is it a 13? 14?
Aluminum or stainless
Are the alum props cupped? or just straight??

Just like the song "little things mean a lot"
A 1/2" and cupped or alum/stainless can make a big difference??
Oh yea trim and tilt can add 1500rpm's easy???
 

puffitu

Chief Petty Officer
Joined
Dec 30, 2018
Messages
555
you say 17p 19p
Is it a 17x13 or 17x131/2
Same with the 19 is it a 13? 14?
Aluminum or stainless
Are the alum props cupped? or just straight??

Just like the song "little things mean a lot"
A 1/2" and cupped or alum/stainless can make a big difference??
Oh yea trim and tilt can add 1500rpm's easy???
There’s a sweet spot the vessel hits when trimmed just right; least resistance.
 

TWPilot

Seaman Apprentice
Joined
Feb 26, 2020
Messages
34
you say 17p 19p
Is it a 17x13 or 17x131/2
Same with the 19 is it a 13? 14?
Aluminum or stainless
Are the alum props cupped? or just straight??

Just like the song "little things mean a lot"
A 1/2" and cupped or alum/stainless can make a big difference??
Oh yea trim and tilt can add 1500rpm's easy???
17X13.5
Aluminum
Cupped
 
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