Merc 2.5L build

**Smalltownbassin** · 11-08-2021, 08:17 AM

Originally Posted by Will hedrick

https://youtu.be/XGZU5TRcEPY

What prop?

**Will hedrick** · 11-08-2021, 08:24 AM

Hill 30 drag 4

**Smalltownbassin** · 12-13-2021, 07:44 AM

*Performance update*

So ive got this frankenbeast broken in now and have a few performance issues which were expected since its my first porting attempt. The first issue is a hesitation of acceleration from idle. I started with stock jetting which was 80 & 82 with a single 84 on 5. Because it acted hungry after 5K i went ahead and upped the mains to 82 on 1,3,4,6 and 84 on 2,5. This jet change seemed to help the mid range but the hesitation was still there and the top end acted hungry still. No plug read yet due to the rich oil mixture still in the tank but ill be doing a hot pull soon with new plugs. The motor is lazy up to 3k but very strong from 3 to 5k. To be honest, its almost identical to a stock ff 200 in the way it runs on my hull. I was talking to some guys on FB about it and they seem to think that by me leaving the dumps in the block stock size for an EE block (basic fishing motor dumps), ive restricted all that port and chest work ive done making it pointless. In my mind i was leaving some bottom end but it sounds like this is whats killing the power over 5k. Simply put, it cant breath. Does this sound about right? It makes sense to me but im still learning. My plan is to pull the powerhead to open the dumps up but dont want to take that leap unless you guys that know more about this than i do say "go for it". So...... What say you S&F? Do i go for it or just be happy with a pretty 200?

**Mrzip** · 12-17-2021, 05:43 PM

What kind of fuel pump you running ?

**Smalltownbassin** · 12-17-2021, 05:48 PM

Oem pulse pump.

**Mrzip** · 12-18-2021, 05:59 AM

Running a modified Mota on a pulse pump? Get a Holley Red Pump. All the Jets need to be the same. Although in the top carb I ran a size bigger. All that does is keep you lubed good up top. That hull is only going run so fast. Probably 88 on top 86 on down. Probably 88 all the way sense I thought about it. Like I said. Hull only going run so fast.

**Smalltownbassin** · 12-18-2021, 07:37 AM

I've got a red holly but was under the impression that the pulse pump is fine up to 6k. I don't want to have to add a return line back to the tank if it's not necessary. What do you think about the dumps in the block?

**rjdubiel** · 12-18-2021, 09:12 AM

I bet the pulse pump keeps up higher than 6k. Pulse.pump or holly has nothing to do with jetting as long as the fuel delivery is correct and not pushing pat the needle and seat and flooding.

**Baker343** · 12-18-2021, 10:15 AM

Have you tried a different set of carbs yet.
WH's with 86 to 88"s for long pulls worked for me.
Really need to read your plugs. How rich a mixture are you running. I don't believe it makes that much of a difference when reading your plugs after a WOT test run.

**Smalltownbassin** · 12-20-2021, 07:21 AM

Originally Posted by Baker343

Have you tried a different set of carbs yet.
WH's with 86 to 88"s for long pulls worked for me.
Really need to read your plugs. How rich a mixture are you running. I don't believe it makes that much of a difference when reading your plugs after a WOT test run.

Yeah ive got a set of WH46's as well as a set of WMH3's from a 7 petal 200. Im wondering if these WMV18's will even let me see much over 6K. They may be restricting fuel by design. idk. Ive got the 46's on another motor at the moment but will try them out on this one before i pull it to do some more grinding on the exhaust dumps. A carb swap is a much easier and quicker change to see how the motor reacts. If its still weak up top with the 46's, ill open the dumps and start testing again. Its funny how strong it is from 3k to 5k but then falls on its face over 5k. I feel like the motor wants to run harder but cant. My break in mixture is 32/1 and my plugs are already too dark to read. I usually keep it at about a 40/1 mix for everyday use. Im at the point now i can top the tank off with little oil added to bring the mix back up to 40/1 and ill put a new set of plugs in then to get a read on them.

**Smalltownbassin** · 01-28-2022, 07:11 AM

Man O man its been a tough start of the year for me! I still haven't been able to get the hull wet since the last thread entry. But...i did go ahead and pull the powerhead to open the exhaust dumps in the bottom of the block. I also took the WMV-18 carbs off and put the WH-46 on. Running the motor on the muffs can be deceiving sometimes but it sure does seem like the 46's woke this SOB up. Im hoping to get it out in the next week or two to see how it actually runs under load but based on what i saw and heard after installing the 46's im pretty optimistic. Ill post up a video once i get it out. Then, im going back to the James Perry block because that MFer aint no slug lol!

**Smalltownbassin** · 01-30-2022, 04:06 PM

https://youtu.be/nfSBIB4WC6s

She is alive!

**Baker343** · 01-30-2022, 05:26 PM

Glad the 46's put a smile on your face.
What size main jets you running

**Smalltownbassin** · 01-30-2022, 05:33 PM

I'll have to look again but I think 80-82 if I remember right.

**Baker343** · 01-30-2022, 05:48 PM

Be careful. Those jets may keep your motor happy with short pulls. I ran 88's with my stock 2.5 4 petal with the exhaust dumps opened to match my 1 piece exhaust plate to keep it happy for 4 hours at WOT.
Make sure you do a plug check after a WOT shut down.
Are you running a 1 or 2 piece exhaust plate