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E38 with 5432 - Normal rpm and boat speed?

Dan W

Member I
Recently noticed our E38 seemed a little sluggish under power, GPS indicated 4.7 knots with the throttle wide open... relatively slack water and calm conditions.

Engine seems to run fine but rpm will not go over 2100 rpm. Linkage adjustment seems ok, there is no more room to push the throttle lever forward. However with the engine in Neutral the tach will go close to 3000 at full throttle.

I'm not really sure where to start... my suspicion is that there is some sort of fuel issue. However the engine starts/runs fine, just won't go past 2100 rpm. Engine temp is 180, I do notice a little steam in exhaust. If injectors are clogged or need maintenance is this a symptom?

A more far fetched idea --- After replacing my cutlass bearing I noticed the shaft seems to turn "stiffer" when bolted to the transmission. I was convinced this was a mis-alignment issue however there was really no unusual vibration with the boat in the water so I figured all was ok - could the friction of a misaligned engine and shaft reduce rpm??

I'm curious as to the normal rpm and boat speed experienced by other E38's, boat has a 16" Martec folding prop...

Dan
 

bayhoss

Member III
From the sound of things it would seem that the engine is running labored. If you can aquire higher rpm and lower engine operating temps. without enganging the prop. then it would seem to be an issue that makes itself present when you shift into gear. The cutlass bearing is a good place to start. As a rule the bearing gets worn and you can feel play in the shaft by pulling it back and forth. If the shaft is scored, then friction will build and increase the load on the motor. If you can get under the boat, then grab the prop and wiggle it back and forth. You should get very little, or no movement. If you have a tangle (crab pot line, discarded line, old fishing line, etc.) that will definitly do it. If you know a diver that will go under the boat, then check for shaft tangles and play. Shaft play will generally not cause the engine to run labored. Tangles will do it every time.

Good Luck!
Frank
E28+ Valinor
 

vbenn

Member III
I had a similar problem with my old boat, a 1984 Seidelmann 295 with Yanmar 2GMF. Problem was caused by a badly corroded mixing elbow which we promptly replaced.

My 1997 E-380 with Yanmar 3JH2BE turns close to 3800 rpm in neutral and 3400 in gear reaching 7.5 kts in calm water. My prop is a 16" Variprop pitched 11 forward, 12 reverse.

Vince Benn
Wild Blue
E-380, #22
 

EGregerson

Member III
cutlass bearing

I think Frank is on to it; if this all started after the bearing was replaced, then.... Sounds like the bearing is too tite.
 

u079721

Contributing Partner
That does sound like a too tight bearing. Maxing out at 2100 rpm could be possible if you were overpropped, but then you would be moving at more than 4.7 kts. If your rpm were 3000, at 4.7 kts, then I would say you were way underpropped.

With the correct prop pitch, on flat water, I think our max speed was 7.4 to 7.6 kts, with a normal cruising speed of 6.8 kts at 2450 rpm.
 

ted_reshetiloff

Contributing Partner
My first guess would be a dirty prop. When mine gets foul I cant get over 2100 RPM. Start by diving the prop. Mixing elbow issue I would think would not allow the neutral rev to 3k. Cutlass or shaft issues would produce a lot of vibration.

I run a two bladed feathering max prop. With everything clean I get 7kts cruising at 2100. Max is 2700 and 7.4-7.5.
 
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Kerry Kukucha

Member II
When we were working through a miriad of engine issues, & after we had put a new prop on (previous owner had put on a prop with wrong diameter & pitch - therefore max top end was only 2,200rpm's), we found that the electric fuel pump on the low pressure side of the fuel system was leaking air.

Prior to the fuel pump replacement, we'd be able to get 2,800 rpm's in neutral, but under load we would be lucky to get 2,000; as I recollect, there wasn't enough fuel getting through (we had also re-built the injector heads as well as serviced the rings/seals, etc. in the high pressure pump, all of which probably helped too). With a new supply pump (&everything else done), we can now get up to 2,800 rpm's underway (which is the spec'd 5432/M40 top end), & at 2,200 cruise along at +/- 6.75 knots.
 

Dan W

Member I
Some Great Suggestions here --- Thank You!!!

Thanks All!!

Some good tips to follow-up on this weekend. I'll let you know how I make out. I think the prop is a great place to start.... make sure nothing is fouled. I really hope that's it...

I don't think the bearing is too tight... the coupling and shaft spins easily by hand when unbolted from the transmission... definitely harder to spin when connected... I think that has to be due to a minor alignment issue and I can spin the transmission flange with one finger. However I don't think the vibration on my boat is unusual, so I can't imagine it's enough to "labor" the engine -- but I don't think I should rule it out just yet.

I think I'll look at fuel and mixing elbow as the next suspects. However the engine seems to "start" and "run" fine... in neutral she revs to 3000 rpm with no issue (should it go higher??).

Again -- thanks to all for the replies. I'll share anything that is learned.
 
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