A Honda Question

[El and Bill]

For starters, we know nothing about engines, except how to maintain them.

We just had a dealer install two new Honda 40's. Old ones were 2001; new are 2006.

Old ones had WOT about 4500 rpm - top speed about 28k. New ones have WOT about 3500 - top speed about 22k. Exactly the same load in the boat (well, a few fried chickens and beers more) and same props with same pitch (took them off old motors, put them on new ones.

Talked to dealer - he can't explain the difference in performance and says they are set at top rpm. Maybe the new engines are set with a lower top rpm.

Is there a setting in the engine that the installer has to adjust to get a higher WOT (and higher speed)? And if so, what is the gizmo he needs to tweak?

We will be taking the engines back to him soon and would like the higher rpm. Thanks, gang.

[Casey]

I would be very surprised if the new engines varied that much from the performance figures of previous engines. For a baseline, what does the owner's manual show for WOT ? If, after some "loosening up time" the engines don't reach proper rpm, it does seem something is amiss (and since you've done the 20-hours service there is enough time on the new engines).

Initial guess would be the props, but if you're using the same props I would think they'd give similar performance.

As I recall you use the ProPulse graphite/adjustable props. Could they have been accidently readjusted to a higher pitch in the removal/reinstallation process? (I suspect not. I also have a ProPulse on the Suzuki; and changing the pitch is rather tedious, probably not done by accident.) Have you tried using different/spare props to see if there is any change?

Final thought. On most of the new engines (for the past several years actually) there are various rpm-limiter systems built into the electronics designed to protect the engine. Might that circuitry be limiting the rpm? (Have dealer check that one....)

Good luck!

Casey
C-Dory Naknek
PS: ...goodness, you get up Early!!!

[Byrdman]

Hey Bill and Casey! Hope all is well with both your families. Bill, how many hours did you get out of your old motors? I will pose this question to Mr. Mitchell at Mitchell Marine in Alexander City. He was one of the very 1st Honda dealers in the SE and still moves a very high volumn of motors due to customer loyalty. Many folks from the coast still come up this way for their upgrades and major work. Will give you a call when I get what ever response he gives. They will be open in about an hour.
Byrdman

[flagold]

On the face of it, it sounds like a rigging problem to me. Very improbable for both engines to not make rpm at the same time . . . Take the cover off one engine and have El go back and forth with the throttle -- find the throttle stop and see if it is hitting the stop as she goes back and forth (idle to wot). You'll see it - it will be the only thing moving. If it isn't hitting the stop, the problem is most probable to be in the cables going up to the engine (throttle quadrant) not opening the throttle fully.

My best guess not looking at it . . .

Good luck!

[journey on]

Just for ducks, the Honda web site says that max HP (40) is at 5500 RPM for those engines. So, 4500 was down from the max HP point, and 3500 is waay down.

Somethings wrong. Not a clue, but they seem geared wrong (propped wrong?)

By the way, those engines are still carbureted. Nothing wrong with that, just a comment.

Boris

[Bearbait]

I agree with Flagold, this looks like a simple problem of not having enough throttle movement.

[lloyds]

Any chance the factory changed the gearing in the latest editions. I can't imagine both engines coming from the factory with the wrong stop adjustment.

[Sea Wolf]

Gearing from 2001 to 2006 is unchanged at 2.09:1. Could also be a fuel restriction (maybe a KINK) induced in switching motors, but the throttle linkage would be the most likely source, assuming prop pitch wasn't changed. My $0.02. Joe.

[El and Bill]

Thanks for the ideas --

Not a fuel restriction problem, since each engine is totally isolated (fuelwise) from the other -- different tanks, filters, fuel lines.

Not the props -- same pitch, same props -- yep, ProPulse and the pitch didn't alter.


We'll check the throttle 'stop' when we get her on the hard at the end of this cruise. When we told the dealer of the problem, after the 20 hour check, he 'adjusted' the throttle to 'full stop' and rpm went up 500 rpm to the 3,500.

Our original engines -- dealer told us they could be set to 5500, but he recommended (from his experience) to set it at 4500. Thought it would give better life to engines, less top end stress, and he knew us well enough to know we're not hot rods. From his 'setting' the rmp, we assumed with these new engines that there is an adjustment that could be made --

Any other thoughts are appreciated -- thanks.

[Rabidfish]

Typically, the engine companies like to prop the engines to run towards the high end with a "light load". This will tend to make it run low-middle with a heavy load.

If you prop the boat to run too low at W.O.T. then you'll be running the engine overloaded, even at mid throttle settings. This will increase time to plane, and increase wear as a result of to much load.

Ideally, I'd like to see it run right at 5000 RPMs with a normal load.
This should put your best cruise speed, and hopefully, range at about 65-75%.

[TyBoo]